A NONHUMAN PRIMATE STUDY (BABOON, PAPIO-HAMADRYAS) TO DETERMINE IF A LONG-ACTING PROGESTOGEN, LEVONORGESTREL BUTANOATE, COMBINED WITH A LONG-ACTING ANDROGEN, TESTOSTERONE BUCICLATE, CAN SUPPRESS SPERMATOGENESIS .1. DOSE-FINDING STUDY

This study in adult male baboons was conducted to establish the dose o f a long-acting progestogen, levonorgestrel butanoate, and that of a l ong-acting androgen, testosterone buciclate, which, when combined, wou ld achieve optimal and prolonged suppression of spermatogenesis. Two i ntramuscular injections of levonorgestrel butanoate at 3-month interva ls and in the dose range 1-8 mg/kg reduced sperm production and plasma concentrations of testosterone, LH and FSH for periods of up to 6 mon ths. The suppression of sperm production was greatest and most prolong ed in the 4 mg/kg group. Two intramuscular injections of testosterone buciclate at 3-month intervals, and at doses of 4 and 8 mg/kg, induced variable changes in circulating levels of testosterone, elevated by t he higher dose, and caused sperm suppression, in some animals to azoos permia. It was concluded that 8 mg/kg testosterone buciclate would pro vide adequate androgen replacement when combined with 4 mg/kg levonorg estrel butanoate as a putative male contraceptive regimen.