The purpose of this research study is to help in the development of male contraception (birth control).

The objective is to conduct a male contraceptive trial in which we will evaluate the suppressive effects of acyline when administered in combination with Testosterone (T) and the progestin depo-medroxyprogesterone acetate (DMPA).

We will be administering combinations of three drugs: Testosterone (T) by gel, Depot Medroxyprogesterone acetate (DMPA) and Acyline to see their effects on sperm production. The T/DMPA/Acyline combination will allow us to determine if the more rapid and complete gonadotropin suppression mediated by the early addition of a GnRH antagonist will accelerate and enhance suppression of spermatogenesis.

In prior studies with testosterone and DMPA these drug, which are hormones, have been found to be safe, and to reversibly suppress sperm counts to zero in about 80% of men. We hope to improve this to 100% of men by adding another drug, Acyline.

Acyline is an GnRH antagonist which blocks the release of LH and FSH from the pituitary. DMPA is approved by the FDA for use as a female contraceptive. The endpoint will be suppression of spermatogenesis to zero (azoospermia) by the end of the treatment phase.

Inclusion Criteria:

• Males between 18-55
• In good general health
• With normal sperm counts
• Willing to use an acceptable form of contraception

Exclusion Criteria:

• Men in poor health
• Significant chronic or acute medical illness
• Skin conditions that might interfere with or be exacerbated by testosterone gel
• Known history of alcohol, illicit drug or anabolic steroid abuse
• Abnormal reproductive function
• Participation in a long-term male contraceptive study within past three months