New antifertility agents active in the rabbit vaginal contraception (RVC) method

Zinc salts in aqueous K-Y Jelly are effective vaginal contraceptives in the rabbit. The minimum effective dose is 54 to 60 mg Zn/ rabbit as acetate, gluconate or lactate. Zinc salts added to suboptimal doses of Ortho-Gynol Jelly or Delfen Cream improves the vaginal contraceptive efficacy of these products. Twenty-seven mg zinc/rabbit as lactate or acetate and 28 mg zinc/rabbit as sulfate or chloride in 0.1 to 0.5 ml of cream or jelly are effective. Gossypol is effective at a dose of 2 mg/rabbit. Although there is some rationale for their use, manganese has no antifertility effect and Valium appears to promote fertility. The rabbit vaginal contraception (RVC) method shows undesirable variation but use of sufficient animals yields logical and reliable results. Artificial insemination instead of breeding appears to decrease variation.