X0306 4 2015-07-17 0 0001297184 Amphastar Pharmaceuticals, Inc. AMPH 0001611281 Shohet Stephen B. C/O AMPHASTAR PHARMACEUTICALS, INC. 11570 6TH STREET RANCHO CUCAMONGA CA 91730 1 0 0 0 Common Stock 2015-07-17 4 M 0 7692 11.68 A 19878 D Common Stock 2015-07-17 4 S 0 7692 17.4107 D 12186 D Stock Option (right to buy) 11.68 2015-07-17 4 M 0 7692 0.00 D 2015-12-18 Common Stock 7692 30770 D The sale reported in this Form 4 was effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 10, 2015. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $17.31 to $17.58, 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. Shares subject to the option are fully vested and immediately exercisable. /s/ Ken Stupak, by power of attorney 2015-07-20