0001297184 2026-06-01 2026-06-01 0001297184 false 8-K 2026-06-01 Amphastar Pharmaceuticals, Inc. DE 001-36509 33-0702205 11570 6th Street Rancho Cucamonga CA 91730 909 980-9484 false false false false Common Stock, par value $0.0001 per share AMPH NASDAQ false