Question

Drug which decreases efficacy of testosterone?

• A. Isoniazid
• B. Ketoconazole
• C. Rifampicin
• D. None

Hint:

An azole antifungal that blocks P450 steroid-synthesis enzymes and acts as an anti-androgen.

Answer 1

The Correct Option is B

Step 1: Testosterone is synthesised through a series of steps involving cytochrome P450 enzymes, including those that convert cholesterol into androgens in the testes and adrenal glands.

Step 2: Ketoconazole is an azole antifungal that inhibits several P450 enzymes involved in steroidogenesis (such as 17,20-lyase and 17-alpha-hydroxylase). By blocking these enzymes it reduces testosterone synthesis, thereby decreasing its effect. This anti-androgen action is why ketoconazole has even been used to lower testosterone in conditions like prostate cancer.

Step 3: Hence ketoconazole is the drug that decreases the efficacy of testosterone, making it the correct answer.

Step 4: Isoniazid and rifampicin are antitubercular drugs; rifampicin is a strong enzyme inducer but is not classically the answer for lowering testosterone action here, and isoniazid does not reduce testosterone efficacy. So options a, c and d are incorrect.