X0306 4 2016-06-15 0 0001297184 Amphastar Pharmaceuticals, Inc. AMPH 0001645326 Zhou Rong C/O AMPHASTAR PHARMACEUTICALS, INC. 11570 6TH STREET RANCHO CUCAMONGA CA 91730 0 1 0 0 EVP, Production Center Common Stock 2016-06-15 4 S 0 1551 15.8503 D 37137 D Common Stock 2016-06-15 4 F 0 146 15.76 D 36991 D Common Stock 99668 I See footnote Common Stock 5000 I See footnote The reported shares were acquired under the Issuer's 2014 Employee Stock Purchase Plan. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $15.82 to $15.88, 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. The reported shares were withheld to satisfy the reporting person's tax liability in connection with the vesting of deferred stock units, or DSUs. 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/ Ken Stupak, by power of attorney 2016-06-17