X0609 4 2026-09-02 0001297184 Amphastar Pharmaceuticals, Inc. AMPH 0001645326 Zhou Rong false C/O AMPHASTAR PHARMACEUTICALS, INC. 11570 6TH STREET RANCHO CUCAMONGA CA 91730 false true false false SENIOR EVP, PRODUCTION CENTER 0 Common Stock 2026-09-02 4 S 0 3187 23.6291 D 169203 D Common Stock 99668 I See footnote Common Stock 5000 I See footnote The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $23.62 to $23.69, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price. Includes 836 shares acquired on May 31, 2026 under the Issuer's 2014 Employee Stock Purchase Plan. The shares are held of record by the Zhou Family Trust for which the reporting person serves as a trustee. The shares are held of record by the reporting person's spouse. /s/ Eva Wen, by power of attorney 2026-09-03