Question:
Which of the following drugs reduces the efficacy of oral contraceptives?
Which of the following drugs reduces the efficacy of oral contraceptives?
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Look for the hepatic enzyme inducer that speeds steroid metabolism.
Updated On: Jun 24, 2026
- Erythromycin
- Griseofulvin
- Cimetidine
- Disulfiram
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The Correct Option is B
Solution and Explanation
Step 1: Oral contraceptives can fail when given with hepatic enzyme inducers, because these drugs speed up the metabolism of estrogen and progesterone, lowering their blood levels. Classic inducers include phenytoin, phenobarbitone, carbamazepine, primidone, rifampicin and griseofulvin.
Step 2: Griseofulvin is a microsomal enzyme inducer. By accelerating the breakdown of the contraceptive steroids it reduces their effectiveness and can cause contraceptive failure. This makes option (b) correct.
Step 3: Erythromycin (a) and cimetidine (c) are enzyme INHIBITORS, so they would tend to raise, not lower, steroid levels. Disulfiram (d) inhibits aldehyde dehydrogenase and is not an inducer that lowers contraceptive efficacy. Hence none of these reduce OCP efficacy the way griseofulvin does.
Step 2: Griseofulvin is a microsomal enzyme inducer. By accelerating the breakdown of the contraceptive steroids it reduces their effectiveness and can cause contraceptive failure. This makes option (b) correct.
Step 3: Erythromycin (a) and cimetidine (c) are enzyme INHIBITORS, so they would tend to raise, not lower, steroid levels. Disulfiram (d) inhibits aldehyde dehydrogenase and is not an inducer that lowers contraceptive efficacy. Hence none of these reduce OCP efficacy the way griseofulvin does.
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