X0306 4 2020-06-14 0 0001297184 Amphastar Pharmaceuticals, Inc. AMPH 0001743927 Liawatidewi Yakob C/O AMPHASTAR PHARMACEUTICALS, INC. 11570 6TH STREET RANCHO CUCAMONGA CA 91730 0 1 0 0 EVP Corp Admin Center Common Stock 2020-06-14 4 F 0 128 19.58 D 45996 D Common Stock 2459 I See footnote The reported shares were withheld to satisfy the reporting person's tax liability in connection with the vesting of restricted stock units, or RSUs. The reported shares are held of record by the Yakob and Sunmoon Trust dated July 25, 2013 for which the reporting person serves as a trustee. /s/ Eva Wen, by power of attorney 2020-06-15