Medical termination of pregnancy in cynomolgus macaques

Background: Although pregnancy is expected during studies of novel contraceptives in non-human primates, gestation, delivery, and lactation remove females from groups for prolonged intervals. As the macaque cervix does not facilitate transcervical surgical termination of pregnancy, we sought to establish a medical termination protocol. Methods: A descriptive case series of outcomes of medical termination of pregnancy up to 32 days gestation in cynomolgus monkeys. Efficacy and time to uterine resolution were determined according to medication, dose, and route of administration. Results: Thirty-seven macaques underwent 65 medical terminations. Over 80% of animals terminated after initial treatment with mifepristone 20 mg intramuscularly (IM). Intrafetal methotrexate was effective for salvage treatment. Medical termination regimens were less effective for animals receiving investigational contraceptive agents. Conclusions: Medical termination for macaques is safe and effective. We recommend a protocol with mifepristone 20 mg IM and misoprostol 200 μg buccally as initial treatment.