Embryotoxicity and maternal serum concentrations of medroxyprogesterone acetate (MPA) in baboons (Papio cynocephalus)

A single dose of MPA (Depo-Provera; Upjohn Co.; USA) was administered intramuscularly on day 27 (+/- 2) of gestation to three dosage groups of pregnant baboons. The dosage expressed as mg/kg corresponded to 1 (2.5 mg/kg), 10 (25 mg/kg) and 40 (100 mg/kg) times the human contraceptive dose equivalent (HDE) based on body weight. Injectable MPA was not teratogenic in baboons at 1x HDE. The teratogenicity was confined to the higher doses which included malformations of the external genitalia at 10x and 40x HDE and adrenal gland hypoplasia at 40x HDE. The maternal serum MPA concentrations were high during the critical period of adrenal and genital development. The pattern of MPA concentrations in maternal sera was similar between animals in the low dose group (10x HDE). In contrast, animals in the high dose group (40x HDE) showed interanimal variations in maternal serum concentrations of MPA. This study has demonstrated that injectable MPA is not teratogenic in baboons at human contraceptive dose equivalent and, even at higher doses, does not result in any nontarget organ malformations.