<?xml version="1.0" encoding="US-ASCII"?>
<!-- Generated by CompSci Transform (tm) - http://www.compsciresources.com -->
<!-- Created: Mon Mar 30 17:04:24 UTC 2026 -->
<xs:schema elementFormDefault="qualified" xmlns:srt-types="http://fasb.org/srt-types/2025" targetNamespace="http://www.pasitheaclinics.com/20251231" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:us-types="http://fasb.org/us-types/2025" xmlns:ktta="http://www.pasitheaclinics.com/20251231" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:dtr="http://www.xbrl.org/dtr/type/2024-01-31" xmlns:xbrli="http://www.xbrl.org/2003/instance">
  <xs:annotation>
    <xs:appinfo>
      <link:linkbaseRef xlink:type="simple" xlink:href="ktta-20251231_lab.xml" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef"/>
      <link:linkbaseRef xlink:type="simple" xlink:href="ktta-20251231_pre.xml" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef"/>
      <link:linkbaseRef xlink:type="simple" xlink:href="ktta-20251231_def.xml" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef"/>
      <link:linkbaseRef xlink:type="simple" xlink:href="ktta-20251231_cal.xml" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef"/>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ConsolidatedBalanceSheet" id="ktta_r_ConsolidatedBalanceSheet">
        <link:definition>995301 - Statement - Consolidated Balance Sheets</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ConsolidatedBalanceSheet_Parentheticals" id="ktta_r_ConsolidatedBalanceSheet_Parentheticals">
        <link:definition>995302 - Statement - Consolidated Balance Sheets (Parentheticals)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ConsolidatedIncomeStatement" id="ktta_r_ConsolidatedIncomeStatement">
        <link:definition>995303 - Statement - Consolidated Statements of Operations and Comprehensive Loss</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ConsolidatedIncomeStatementAlt0" id="ktta_r_ConsolidatedIncomeStatementAlt0">
        <link:definition>995303 - Statement - Consolidated Statements of Operations and Comprehensive Loss Alternate 0</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ShareholdersEquityType2or3" id="ktta_r_ShareholdersEquityType2or3">
        <link:definition>995304 - Statement - Consolidated Statements of Changes in Stockholders&#8217; Equity</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ConsolidatedCashFlow" id="ktta_r_ConsolidatedCashFlow">
        <link:definition>995305 - Statement - Consolidated Statements of Cash Flows</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/NatureoftheOrganizationandBusiness" id="ktta_r_NatureoftheOrganizationandBusiness">
        <link:definition>995306 - Disclosure - Nature of the Organization and Business</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/SummaryofSignificantAccountingPoliciesandNewAccountingStandards" id="ktta_r_SummaryofSignificantAccountingPoliciesandNewAccountingStandards">
        <link:definition>995307 - Disclosure - Summary of Significant Accounting Policies and New Accounting Standards</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/PropertyandEquipment" id="ktta_r_PropertyandEquipment">
        <link:definition>995308 - Disclosure - Property and Equipment</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/Leases" id="ktta_r_Leases">
        <link:definition>995309 - Disclosure - Leases</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/IntangibleAssetsandGoodwill" id="ktta_r_IntangibleAssetsandGoodwill">
        <link:definition>995310 - Disclosure - Intangible Assets and Goodwill</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/StockholdersEquity" id="ktta_r_StockholdersEquity">
        <link:definition>995311 - Disclosure - Stockholders&#8217; Equity</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/StockOptions" id="ktta_r_StockOptions">
        <link:definition>995312 - Disclosure - Stock Options</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/Warrants" id="ktta_r_Warrants">
        <link:definition>995313 - Disclosure - Warrants</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/IncomeTaxes" id="ktta_r_IncomeTaxes">
        <link:definition>995314 - Disclosure - Income Taxes</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/NetLossPerCommonShare" id="ktta_r_NetLossPerCommonShare">
        <link:definition>995315 - Disclosure - Net Loss Per Common Share</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/RelatedPartyTransactions" id="ktta_r_RelatedPartyTransactions">
        <link:definition>995316 - Disclosure - Related Party Transactions</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/CommitmentsandContingencies" id="ktta_r_CommitmentsandContingencies">
        <link:definition>995317 - Disclosure - Commitments and Contingencies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/SegmentInformation" id="ktta_r_SegmentInformation">
        <link:definition>995318 - Disclosure - Segment Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/SubsequentEvents" id="ktta_r_SubsequentEvents">
        <link:definition>995319 - Disclosure - Subsequent Events</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/AccountingPoliciesByPolicy" id="ktta_r_AccountingPoliciesByPolicy">
        <link:definition>996000 - Disclosure - Accounting Policies, by Policy (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/SummaryofSignificantAccountingPoliciesandNewAccountingStandardsTables" id="ktta_r_SummaryofSignificantAccountingPoliciesandNewAccountingStandardsTables">
        <link:definition>996001 - Disclosure - Summary of Significant Accounting Policies and New Accounting Standards (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/PropertyandEquipmentTables" id="ktta_r_PropertyandEquipmentTables">
        <link:definition>996002 - Disclosure - Property and Equipment (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/LeasesTables" id="ktta_r_LeasesTables">
        <link:definition>996003 - Disclosure - Leases (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/IntangibleAssetsandGoodwillTables" id="ktta_r_IntangibleAssetsandGoodwillTables">
        <link:definition>996004 - Disclosure - Intangible Assets and Goodwill (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/StockOptionsTables" id="ktta_r_StockOptionsTables">
        <link:definition>996005 - Disclosure - Stock Options (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/WarrantsTables" id="ktta_r_WarrantsTables">
        <link:definition>996006 - Disclosure - Warrants (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/IncomeTaxesTables" id="ktta_r_IncomeTaxesTables">
        <link:definition>996007 - Disclosure - Income Taxes (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/SegmentInformationTables" id="ktta_r_SegmentInformationTables">
        <link:definition>996008 - Disclosure - Segment Information (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/NatureoftheOrganizationandBusinessDetails" id="ktta_r_NatureoftheOrganizationandBusinessDetails">
        <link:definition>996009 - Disclosure - Nature of the Organization and Business (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/SummaryofSignificantAccountingPoliciesandNewAccountingStandardsDetails" id="ktta_r_SummaryofSignificantAccountingPoliciesandNewAccountingStandardsDetails">
        <link:definition>996010 - Disclosure - Summary of Significant Accounting Policies and New Accounting Standards (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ScheduleofMeasuredatFairValueonaRecurringBasisTable" id="ktta_r_ScheduleofMeasuredatFairValueonaRecurringBasisTable">
        <link:definition>996011 - Disclosure - Summary of Significant Accounting Policies and New Accounting Standards - Schedule of Measured at Fair Value on a Recurring Basis (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ScheduleofReconciliationoftheLevel3RepresentativeWarrantLiabilitiesTable" id="ktta_r_ScheduleofReconciliationoftheLevel3RepresentativeWarrantLiabilitiesTable">
        <link:definition>996012 - Disclosure - Summary of Significant Accounting Policies and New Accounting Standards - Schedule of Reconciliation of the Level 3 Representative Warrant Liabilities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ScheduleofNetLossPerShareTable" id="ktta_r_ScheduleofNetLossPerShareTable">
        <link:definition>996013 - Disclosure - Summary of Significant Accounting Policies and New Accounting Standards - Schedule of Net Loss Per Share (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ScheduleofRelevantTranslationRatesTable" id="ktta_r_ScheduleofRelevantTranslationRatesTable">
        <link:definition>996014 - Disclosure - Summary of Significant Accounting Policies and New Accounting Standards - Schedule of Relevant Translation Rates (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/PropertyandEquipmentDetails" id="ktta_r_PropertyandEquipmentDetails">
        <link:definition>996015 - Disclosure - Property and Equipment (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ScheduleofPropertyandEquipmentNetTable" id="ktta_r_ScheduleofPropertyandEquipmentNetTable">
        <link:definition>996016 - Disclosure - Property and Equipment - Schedule of Property and Equipment, Net (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/LeasesDetails" id="ktta_r_LeasesDetails">
        <link:definition>996017 - Disclosure - Leases (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ScheduleofROUAssetsandLeaseLiabilitiesTable" id="ktta_r_ScheduleofROUAssetsandLeaseLiabilitiesTable">
        <link:definition>996018 - Disclosure - Leases - Schedule of ROU Assets and Lease Liabilities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/IntangibleAssetsandGoodwillDetails" id="ktta_r_IntangibleAssetsandGoodwillDetails">
        <link:definition>996019 - Disclosure - Intangible Assets and Goodwill (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ScheduleofIntangibleAssetsNetTable" id="ktta_r_ScheduleofIntangibleAssetsNetTable">
        <link:definition>996020 - Disclosure - Intangible Assets and Goodwill - Schedule of Intangible Assets, Net (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ScheduleofFutureExpectedAmortizationExpenseofIntangibleAssetsTable" id="ktta_r_ScheduleofFutureExpectedAmortizationExpenseofIntangibleAssetsTable">
        <link:definition>996021 - Disclosure - Intangible Assets and Goodwill - Schedule of Future Expected Amortization Expense of Intangible Assets (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/StockholdersEquityDetails" id="ktta_r_StockholdersEquityDetails">
        <link:definition>996022 - Disclosure - Stockholders&#8217; Equity (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/StockOptionsDetails" id="ktta_r_StockOptionsDetails">
        <link:definition>996023 - Disclosure - Stock Options (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ScheduleofStockOptionActivityTable" id="ktta_r_ScheduleofStockOptionActivityTable">
        <link:definition>996024 - Disclosure - Stock Options - Schedule of Stock Option Activity (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ScheduleofWeightedAverageAssumptionsTable" id="ktta_r_ScheduleofWeightedAverageAssumptionsTable">
        <link:definition>996025 - Disclosure - Stock Options - Schedule of Weighted Average Assumptions (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/WarrantsDetails" id="ktta_r_WarrantsDetails">
        <link:definition>996026 - Disclosure - Warrants (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ScheduleofWarrantActivityTable" id="ktta_r_ScheduleofWarrantActivityTable">
        <link:definition>996027 - Disclosure - Warrants - Schedule of Warrant Activity (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ScheduleofWarrantsExercisableTable" id="ktta_r_ScheduleofWarrantsExercisableTable">
        <link:definition>996028 - Disclosure - Warrants - Schedule of Warrants Exercisable (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/IncomeTaxesDetails" id="ktta_r_IncomeTaxesDetails">
        <link:definition>996029 - Disclosure - Income Taxes (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ScheduleofDeferredTaxAssetsTable" id="ktta_r_ScheduleofDeferredTaxAssetsTable">
        <link:definition>996030 - Disclosure - Income Taxes - Schedule of Deferred Tax Assets (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ScheduleofReconciliationoftheFederalIncomeTaxRateTable" id="ktta_r_ScheduleofReconciliationoftheFederalIncomeTaxRateTable">
        <link:definition>996031 - Disclosure - Income Taxes - Schedule of Reconciliation of the Federal Income Tax Rate (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/NetLossPerCommonShareDetails" id="ktta_r_NetLossPerCommonShareDetails">
        <link:definition>996032 - Disclosure - Net Loss Per Common Share (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/RelatedPartyTransactionsDetails" id="ktta_r_RelatedPartyTransactionsDetails">
        <link:definition>996033 - Disclosure - Related Party Transactions (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/SegmentInformationDetails" id="ktta_r_SegmentInformationDetails">
        <link:definition>996034 - Disclosure - Segment Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/ScheduleofReconciliationtotheConsolidatedNetLossTable" id="ktta_r_ScheduleofReconciliationtotheConsolidatedNetLossTable">
        <link:definition>996035 - Disclosure - Segment Information - Schedule of Reconciliation to the Consolidated Net Loss (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/SubsequentEventsDetails" id="ktta_r_SubsequentEventsDetails">
        <link:definition>996036 - Disclosure - Subsequent Events (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.pasitheaclinics.com/role/DocumentAndEntityInformation" id="DocumentAndEntityInformation">
        <link:definition>000 - Document - Document And Entity Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
      </link:roleType>
    </xs:appinfo>
  </xs:annotation>
  <xs:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd"/>
  <xs:import namespace="http://fasb.org/us-types/2025" schemaLocation="https://xbrl.fasb.org/us-gaap/2025/elts/us-types-2025.xsd"/>
  <xs:import namespace="http://www.xbrl.org/dtr/type/2024-01-31" schemaLocation="https://www.xbrl.org/dtr/type/2024-01-31/types.xsd"/>
  <xs:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd"/>
  <xs:import namespace="http://fasb.org/srt-types/2025" schemaLocation="https://xbrl.fasb.org/srt/2025/elts/srt-types-2025.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/sic/2025" schemaLocation="https://xbrl.sec.gov/sic/2025/sic-2025.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/cyd-af/2025" schemaLocation="https://xbrl.sec.gov/cyd/2025/cyd-af-2025.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/ecd/2025" schemaLocation="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/ecd-sub/2025" schemaLocation="https://xbrl.sec.gov/ecd/2025/ecd-sub-2025.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/dei-sub/2025" schemaLocation="https://xbrl.sec.gov/dei/2025/dei-sub-2025.xsd"/>
  <xs:element name="ScheduleOfMeasuredAtFairValueOnARecurringBasisAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ScheduleOfMeasuredAtFairValueOnARecurringBasisAbstract"/>
  <xs:element name="ScheduleOfReconciliationOfTheLevel3RepresentativeWarrantLiabilitiesAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ScheduleOfReconciliationOfTheLevel3RepresentativeWarrantLiabilitiesAbstract"/>
  <xs:element name="ScheduleOfNetLossPerShareAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ScheduleOfNetLossPerShareAbstract"/>
  <xs:element name="ScheduleOfRelevantTranslationRatesAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ScheduleOfRelevantTranslationRatesAbstract"/>
  <xs:element name="ScheduleOfPropertyAndEquipmentNetAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ScheduleOfPropertyAndEquipmentNetAbstract"/>
  <xs:element name="ScheduleOfRouAssetsAndLeaseLiabilitiesAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ScheduleOfRouAssetsAndLeaseLiabilitiesAbstract"/>
  <xs:element name="ScheduleOfIntangibleAssetsNetAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ScheduleOfIntangibleAssetsNetAbstract"/>
  <xs:element name="ScheduleOfStockOptionActivityAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ScheduleOfStockOptionActivityAbstract"/>
  <xs:element name="ScheduleOfWarrantActivityAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ScheduleOfWarrantActivityAbstract"/>
  <xs:element name="ScheduleOfWarrantsExercisableAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ScheduleOfWarrantsExercisableAbstract"/>
  <xs:element name="ScheduleOfDeferredTaxAssetsAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ScheduleOfDeferredTaxAssetsAbstract"/>
  <xs:element name="ScheduleOfReconciliationToTheConsolidatedNetLossAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ScheduleOfReconciliationToTheConsolidatedNetLossAbstract"/>
  <xs:element name="LiabilitiesAbstract0" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_LiabilitiesAbstract0"/>
  <xs:element name="WarrantLiabilitiesPlacementAgentWarrants" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item" id="ktta_WarrantLiabilitiesPlacementAgentWarrants"/>
  <xs:element name="RealizedForeignCurrencyTranslationLossFromDissolutionOfSubsidiaries" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item" id="ktta_RealizedForeignCurrencyTranslationLossFromDissolutionOfSubsidiaries"/>
  <xs:element name="ChangeInFairValueOfDerivativeWarrantLiability" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item" id="ktta_ChangeInFairValueOfDerivativeWarrantLiability"/>
  <xs:element name="StockIssuedDuringPeriodValueMay2025PublicOfferingOfCommonStockAndWarrantsNet" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item" id="ktta_StockIssuedDuringPeriodValueMay2025PublicOfferingOfCommonStockAndWarrantsNet"/>
  <xs:element name="StockIssuedDuringPeriodSharesPublicOfferingOfCommonStockAndWarrantsNet" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_StockIssuedDuringPeriodSharesPublicOfferingOfCommonStockAndWarrantsNet"/>
  <xs:element name="StockIssuedDuringPeriodValueDecember2025PublicOfferingOfCommonStockAndPrefundedWarrantsNet" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item" id="ktta_StockIssuedDuringPeriodValueDecember2025PublicOfferingOfCommonStockAndPrefundedWarrantsNet"/>
  <xs:element name="StockIssuedDuringPeriodSharesPublicOfferingOfCommonStockAndPrefundedWarrantsNet" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_StockIssuedDuringPeriodSharesPublicOfferingOfCommonStockAndPrefundedWarrantsNet"/>
  <xs:element name="StockIssuedDuringPeriodValueIssuanceOfCommonStockFromTheExerciseOfWarrantsNet" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item" id="ktta_StockIssuedDuringPeriodValueIssuanceOfCommonStockFromTheExerciseOfWarrantsNet"/>
  <xs:element name="StockIssuedDuringPeriodIssuanceOfCommonStockFromTheExerciseOfWarrantsNet" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_StockIssuedDuringPeriodIssuanceOfCommonStockFromTheExerciseOfWarrantsNet"/>
  <xs:element name="AdjustmentToAdditionalPaidInCapitalIssuanceOfPrefundedAndCommonWarrantsNet" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item" id="ktta_AdjustmentToAdditionalPaidInCapitalIssuanceOfPrefundedAndCommonWarrantsNet"/>
  <xs:element name="StockIssuedDuringPeriodIssuanceOfCommonStockFromTheExerciseOfPrefundedWarrantsNet" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_StockIssuedDuringPeriodIssuanceOfCommonStockFromTheExerciseOfPrefundedWarrantsNet"/>
  <xs:element name="GainLossOnAssetWriteoff" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item" id="ktta_GainLossOnAssetWriteoff"/>
  <xs:element name="ProceedsFromExercisesOfPrefundedWarrants" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item" id="ktta_ProceedsFromExercisesOfPrefundedWarrants"/>
  <xs:element name="DeemedDividendWarrantModification" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item" id="ktta_DeemedDividendWarrantModification"/>
  <xs:element name="WarrantsTextBlock" type="dtr:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_WarrantsTextBlock"/>
  <xs:element name="DefinedContributionSavingsPlanPolicyTextBlock" type="dtr:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_DefinedContributionSavingsPlanPolicyTextBlock"/>
  <xs:element name="GrantsPolicyTextBlock" type="dtr:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_GrantsPolicyTextBlock"/>
  <xs:element name="CommonStockWarrantsPolicyTextBlock" type="dtr:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_CommonStockWarrantsPolicyTextBlock"/>
  <xs:element name="WarrantLiabilityPolicyTextBlock" type="dtr:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_WarrantLiabilityPolicyTextBlock"/>
  <xs:element name="TranslationOfForeignOperationsPolicyTextBlock" type="dtr:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_TranslationOfForeignOperationsPolicyTextBlock"/>
  <xs:element name="RecentlyAdoptedAccountingPronouncementsPolicyTextBlock" type="dtr:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_RecentlyAdoptedAccountingPronouncementsPolicyTextBlock"/>
  <xs:element name="ScheduleOfStockholdersEquityNoteWarrantsTableTextBlock" type="dtr:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ScheduleOfStockholdersEquityNoteWarrantsTableTextBlock"/>
  <xs:element name="SummaryofSignificantAccountingPoliciesandNewAccountingStandardsScheduleofMeasuredatFairValueonaRecurringBasisDetailsTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem" id="ktta_SummaryofSignificantAccountingPoliciesandNewAccountingStandardsScheduleofMeasuredatFairValueonaRecurringBasisDetailsTable"/>
  <xs:element name="SummaryofSignificantAccountingPoliciesandNewAccountingStandardsScheduleofNetLossPerShareDetailsTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem" id="ktta_SummaryofSignificantAccountingPoliciesandNewAccountingStandardsScheduleofNetLossPerShareDetailsTable"/>
  <xs:element name="SummaryofSignificantAccountingPoliciesandNewAccountingStandardsScheduleofRelevantTranslationRatesDetailsTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem" id="ktta_SummaryofSignificantAccountingPoliciesandNewAccountingStandardsScheduleofRelevantTranslationRatesDetailsTable"/>
  <xs:element name="ForeignCurrencyTranslationClosingRate" type="xbrli:pureItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item" id="ktta_ForeignCurrencyTranslationClosingRate"/>
  <xs:element name="ForeignCurrencyAverageRateForPeriodEnded" type="xbrli:pureItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item" id="ktta_ForeignCurrencyAverageRateForPeriodEnded"/>
  <xs:element name="IntangibleAssetsandGoodwillScheduleofIntangibleAssetsNetDetailsTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem" id="ktta_IntangibleAssetsandGoodwillScheduleofIntangibleAssetsNetDetailsTable"/>
  <xs:element name="StockOptionsScheduleofStockOptionActivityDetailsTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem" id="ktta_StockOptionsScheduleofStockOptionActivityDetailsTable"/>
  <xs:element name="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsGrantsInWeightedAverageRemainingContractualTerm" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsGrantsInWeightedAverageRemainingContractualTerm"/>
  <xs:element name="WarrantsScheduleofWarrantActivityDetailsTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem" id="ktta_WarrantsScheduleofWarrantActivityDetailsTable"/>
  <xs:element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumberEnding" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item" id="ktta_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumberEnding"/>
  <xs:element name="ShareBasedCompensationArrangementByShareBasedPaymentsAwardNonOptionEquityInstrumentsOutstandingExercisePricePerShare" type="dtr:perShareItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item" id="ktta_ShareBasedCompensationArrangementByShareBasedPaymentsAwardNonOptionEquityInstrumentsOutstandingExercisePricePerShare"/>
  <xs:element name="ShareBasedCompensationArrangementByShareBasedPaymentsAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice" type="dtr:perShareItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item" id="ktta_ShareBasedCompensationArrangementByShareBasedPaymentsAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice"/>
  <xs:element name="ShareBasedCompensationArrangementByShareBasedPaymentsAwardNonOptionEquityInstrumentsGrantedExercisePricePerShare" type="dtr:perShareItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ShareBasedCompensationArrangementByShareBasedPaymentsAwardNonOptionEquityInstrumentsGrantedExercisePricePerShare"/>
  <xs:element name="ShareBasedCompensationArrangementByShareBasedPaymentsAwardNonOptionEquityInstrumentsGrantedWeightedAverageExercisePrice" type="dtr:perShareItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ShareBasedCompensationArrangementByShareBasedPaymentsAwardNonOptionEquityInstrumentsGrantedWeightedAverageExercisePrice"/>
  <xs:element name="ShareBasedCompensationArrangementByShareBasedPaymentsAwardNonOptionEquityInstrumentsExpiredWeightedAverageExercisePrice" type="dtr:perShareItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ShareBasedCompensationArrangementByShareBasedPaymentsAwardNonOptionEquityInstrumentsExpiredWeightedAverageExercisePrice"/>
  <xs:element name="ShareBasedCompensationArrangementByShareBasedPaymentsAwardNonOptionEquityInstrumentsExercisedWeightedAverageExercisePrice" type="dtr:perShareItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ShareBasedCompensationArrangementByShareBasedPaymentsAwardNonOptionEquityInstrumentsExercisedWeightedAverageExercisePrice"/>
  <xs:element name="ShareBasedPaymentArrangementNonOptionExercisePriceRangeOutstandingWeightedAverageRemainingContractualTerm" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ShareBasedPaymentArrangementNonOptionExercisePriceRangeOutstandingWeightedAverageRemainingContractualTerm"/>
  <xs:element name="DeferredTaxAssetsAmortization" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item" id="ktta_DeferredTaxAssetsAmortization"/>
  <xs:element name="DeferredTaxLiabilitiesAmortization" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item" id="ktta_DeferredTaxLiabilitiesAmortization"/>
  <xs:element name="DeferredTaxLiabilitiesDepreciation" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item" id="ktta_DeferredTaxLiabilitiesDepreciation"/>
  <xs:element name="EffectiveIncomeTaxRateReconciliationReturnToProvisionAdjustment" type="dtr:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_EffectiveIncomeTaxRateReconciliationReturnToProvisionAdjustment"/>
  <xs:element name="EffectiveIncomeTaxRateReconciliationPermanentItems" type="dtr:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_EffectiveIncomeTaxRateReconciliationPermanentItems"/>
  <xs:element name="PreclinicalResearch" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item" id="ktta_PreclinicalResearch"/>
  <xs:element name="CMCSegmentExpenses" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item" id="ktta_CMCSegmentExpenses"/>
  <xs:element name="ClinicalDevelopment" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item" id="ktta_ClinicalDevelopment"/>
  <xs:element name="TotalOperatingAndSegmentExpenses" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item" id="ktta_TotalOperatingAndSegmentExpenses"/>
  <xs:element name="WorkingCapital" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item" id="ktta_WorkingCapital"/>
  <xs:element name="SummaryofSignificantAccountingPoliciesandNewAccountingStandardsDetailsTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem" id="ktta_SummaryofSignificantAccountingPoliciesandNewAccountingStandardsDetailsTable"/>
  <xs:element name="BookValueOfAssetsSoldGross" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item" id="ktta_BookValueOfAssetsSoldGross"/>
  <xs:element name="StockholdersEquityDetailsTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem" id="ktta_StockholdersEquityDetailsTable"/>
  <xs:element name="NumberofAggregateAuthorizedShares" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_NumberofAggregateAuthorizedShares"/>
  <xs:element name="CommonStockAvailableForIssuance" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item" id="ktta_CommonStockAvailableForIssuance"/>
  <xs:element name="NetProceedsAfterDeductingPlacement" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item" id="ktta_NetProceedsAfterDeductingPlacement"/>
  <xs:element name="WarrantsExercisedShares" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item" id="ktta_WarrantsExercisedShares"/>
  <xs:element name="CommissionAggregateGrossProceeds" type="dtr:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_CommissionAggregateGrossProceeds"/>
  <xs:element name="GrossProceeds" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item" id="ktta_GrossProceeds"/>
  <xs:element name="IssuedDuringPeriodSharesIssuanceOfCommonStockFromTheExerciseOfPrefundedWarrantsNet" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_IssuedDuringPeriodSharesIssuanceOfCommonStockFromTheExerciseOfPrefundedWarrantsNet"/>
  <xs:element name="BeneficialOwnershipLimitationEffectiveDays" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_BeneficialOwnershipLimitationEffectiveDays"/>
  <xs:element name="AggregateNetProceeds" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item" id="ktta_AggregateNetProceeds"/>
  <xs:element name="CommonStockExercisePrice" type="dtr:perShareItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item" id="ktta_CommonStockExercisePrice"/>
  <xs:element name="StockOptionsDetailsTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem" id="ktta_StockOptionsDetailsTable"/>
  <xs:element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsStrikePrice" type="xbrli:decimalItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item" id="ktta_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsStrikePrice"/>
  <xs:element name="WarrantsDetailsTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem" id="ktta_WarrantsDetailsTable"/>
  <xs:element name="DividendWarrantModification" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item" id="ktta_DividendWarrantModification"/>
  <xs:element name="UnderwritersRepresentativeWarrantsIssued" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_UnderwritersRepresentativeWarrantsIssued"/>
  <xs:element name="ClassOfWarrantOrRightsExercisable" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ClassOfWarrantOrRightsExercisable"/>
  <xs:element name="NumberOfAdditionalWarrants" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_NumberOfAdditionalWarrants"/>
  <xs:element name="IncomeTaxesDetailsTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem" id="ktta_IncomeTaxesDetailsTable"/>
  <xs:element name="NetLossPerCommonShareDetailsTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem" id="ktta_NetLossPerCommonShareDetailsTable"/>
  <xs:element name="RelatedPartyTransactionsDetailsTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem" id="ktta_RelatedPartyTransactionsDetailsTable"/>
  <xs:element name="SubsequentEventsDetailsTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem" id="ktta_SubsequentEventsDetailsTable"/>
  <xs:element name="ClassOfWarrantOrRightNumberOfSecuritiesExercised" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item" id="ktta_ClassOfWarrantOrRightNumberOfSecuritiesExercised"/>
  <xs:element name="ATMAgreementMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ATMAgreementMember"/>
  <xs:element name="AlloMekWarrantsMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_AlloMekWarrantsMember"/>
  <xs:element name="Alpha5WarrantsMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_Alpha5WarrantsMember"/>
  <xs:element name="AtTheMarketAgreementWithHCWainwrightMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_AtTheMarketAgreementWithHCWainwrightMember"/>
  <xs:element name="CommonStockParValue00001PerShareMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_CommonStockParValue00001PerShareMember"/>
  <xs:element name="ConsultantMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ConsultantMember"/>
  <xs:element name="December2025PreFundedWarrantSharesMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_December2025PreFundedWarrantSharesMember"/>
  <xs:element name="December2025PreFundedWarrantsMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_December2025PreFundedWarrantsMember"/>
  <xs:element name="DecemberTwoThousandTwentyFIVEPreFundedWarrantsMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_DecemberTwoThousandTwentyFIVEPreFundedWarrantsMember"/>
  <xs:element name="DecemberTwoThousandTwentyFivePlacementAgentWarrantsMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_DecemberTwoThousandTwentyFivePlacementAgentWarrantsMember"/>
  <xs:element name="DecemberTwoThousandTwentyFivePublicOfferingMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_DecemberTwoThousandTwentyFivePublicOfferingMember"/>
  <xs:element name="DerivativeWarrantLiabilitiesMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_DerivativeWarrantLiabilitiesMember"/>
  <xs:element name="ExercisePrice12000Member" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ExercisePrice12000Member"/>
  <xs:element name="ExercisePrice12500Member" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ExercisePrice12500Member"/>
  <xs:element name="ExercisePrice175Member" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ExercisePrice175Member"/>
  <xs:element name="ExercisePrice2000Member" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ExercisePrice2000Member"/>
  <xs:element name="ExercisePrice3760Member" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ExercisePrice3760Member"/>
  <xs:element name="ExercisePrice385Member" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ExercisePrice385Member"/>
  <xs:element name="ExercisePrice813Member" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ExercisePrice813Member"/>
  <xs:element name="ExercisePriceFivePointOneThreeMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ExercisePriceFivePointOneThreeMember"/>
  <xs:element name="ExercisePriceOnePoitFourZeroMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ExercisePriceOnePoitFourZeroMember"/>
  <xs:element name="FederalMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_FederalMember"/>
  <xs:element name="IPOWarrantsMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_IPOWarrantsMember"/>
  <xs:element name="May2025PlacementAgentWarrantsMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_May2025PlacementAgentWarrantsMember"/>
  <xs:element name="May2025PreFundedWarrantMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_May2025PreFundedWarrantMember"/>
  <xs:element name="MayTwoThousandTwentyFiveWarrantsMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_MayTwoThousandTwentyFiveWarrantsMember"/>
  <xs:element name="MedicalAndOfficeEquipmentMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_MedicalAndOfficeEquipmentMember"/>
  <xs:element name="OwnershipLimitationMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_OwnershipLimitationMember"/>
  <xs:element name="PIPEWarrantsMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_PIPEWarrantsMember"/>
  <xs:element name="PlacementAgentWarrantsMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_PlacementAgentWarrantsMember"/>
  <xs:element name="PreFundedWarrantsMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_PreFundedWarrantsMember"/>
  <xs:element name="PrivateInvestmentInPublicEquityPIPEWarrantsMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_PrivateInvestmentInPublicEquityPIPEWarrantsMember"/>
  <xs:element name="ProfSteinmanMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_ProfSteinmanMember"/>
  <xs:element name="PublicWarrantLiabilitiesMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_PublicWarrantLiabilitiesMember"/>
  <xs:element name="PublicWarrantMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_PublicWarrantMember"/>
  <xs:element name="RepresentativeWarrantLiabilitiesMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_RepresentativeWarrantLiabilitiesMember"/>
  <xs:element name="RepresentativeWarrantMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_RepresentativeWarrantMember"/>
  <xs:element name="SecuritiesPurchaseAgreementsMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_SecuritiesPurchaseAgreementsMember"/>
  <xs:element name="September2024PreFundedWarrantsMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_September2024PreFundedWarrantsMember"/>
  <xs:element name="September2024PrivatePlacementMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_September2024PrivatePlacementMember"/>
  <xs:element name="SeriesAWarrantsMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_SeriesAWarrantsMember"/>
  <xs:element name="SeriesBWarrantsMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_SeriesBWarrantsMember"/>
  <xs:element name="SeriesCCommonMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_SeriesCCommonMember"/>
  <xs:element name="SeriesCWarrantsMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_SeriesCWarrantsMember"/>
  <xs:element name="SeriesDCommonWarrantMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_SeriesDCommonWarrantMember"/>
  <xs:element name="SeriesDWarrantsMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_SeriesDWarrantsMember"/>
  <xs:element name="StockBasedCompensationMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_StockBasedCompensationMember"/>
  <xs:element name="StockOptionPlanMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_StockOptionPlanMember"/>
  <xs:element name="TwoThousandTwentyOneIncentivePlanMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_TwoThousandTwentyOneIncentivePlanMember"/>
  <xs:element name="TwoThousandTwentyOneMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_TwoThousandTwentyOneMember"/>
  <xs:element name="TwoThousandTwentyThreeIncentivePlanMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_TwoThousandTwentyThreeIncentivePlanMember"/>
  <xs:element name="TwoThousandTwentyThreeMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_TwoThousandTwentyThreeMember"/>
  <xs:element name="TwoThousandTwentyThreePlanToEmployeeMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_TwoThousandTwentyThreePlanToEmployeeMember"/>
  <xs:element name="TwoThousandTwentyThreeStockIncentivePlanMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_TwoThousandTwentyThreeStockIncentivePlanMember"/>
  <xs:element name="WarrantDerivativeLiabilityMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_WarrantDerivativeLiabilityMember"/>
  <xs:element name="Warrants1Member" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_Warrants1Member"/>
  <xs:element name="WarrantsToPurchaseSharesOfCommonStockParValue00001PerShareMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_WarrantsToPurchaseSharesOfCommonStockParValue00001PerShareMember"/>
<!-- [WMV6][qJYlV1hY+HH1z/i3h+tm9kNQinbBHxR9aFT2Cj4yJwpjHKn2sPgsrbEVCRc/A6LJtWbft4nrWAK5GD9MDhykmvrlpZ+EHasalNB71YCaJ5bBYXA7KP0bl0SkS1qHrkyR52UDY2prcpYsQfhvS10jx8w3WQKBOygFfVs3GXOYONPsSBtbQvqIsuXIkySWFLbZO0q2TtVlQXCbieQz4T3IPoL2jlMFp7Vfbdlbk7xaSCXQXo5XeujVOs1sqnklho5OHql6jEgmQAL9s8ljuacWxZOLqHEkpoSwdvQ7lHVF09UTO4cnK5dF4MR42XmXmHrR+obdqeImRuhJaJhTQtu9FJGYtIfhuGLZ8I6vUxkJMLV2sb5pJvYedO0=] CSR-->
  <xs:element name="DocumentAndEntityInformationAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ktta_DocumentAndEntityInformationAbstract"/>
</xs:schema>
