Question:medium
Which of the following drugs reduces the efficacy of oral contraceptives?
Which of the following drugs reduces the efficacy of oral contraceptives?
Show Hint
Look for the hepatic enzyme inducer that speeds steroid metabolism.
Updated On: Jun 24, 2026
- Erythromycin
- Griseofulvin
- Cimetidine
- Disulfiram
Show Solution
The Correct Option is B
Solution and Explanation
Step 1: The question reduces to identifying the one drug that ramps up liver metabolism, since faster steroid clearance is what undermines the pill.
Step 2: Griseofulvin is a well known inducer of hepatic microsomal enzymes. Greater enzyme activity means estrogen and progesterone are degraded more quickly, dropping their levels below the threshold needed for reliable contraception. That is why it can lead to breakthrough ovulation and pregnancy, confirming option (b).
Step 3: The other choices behave oppositely or are unrelated. Erythromycin and cimetidine inhibit cytochrome enzymes, which slows steroid breakdown rather than speeding it. Disulfiram blocks aldehyde dehydrogenase and has no enzyme-inducing effect on the pill.
Step 4: Only an inducer threatens contraceptive cover, so the inhibitors and disulfiram are eliminated.
\[\boxed{\text{Griseofulvin}}\]
Step 2: Griseofulvin is a well known inducer of hepatic microsomal enzymes. Greater enzyme activity means estrogen and progesterone are degraded more quickly, dropping their levels below the threshold needed for reliable contraception. That is why it can lead to breakthrough ovulation and pregnancy, confirming option (b).
Step 3: The other choices behave oppositely or are unrelated. Erythromycin and cimetidine inhibit cytochrome enzymes, which slows steroid breakdown rather than speeding it. Disulfiram blocks aldehyde dehydrogenase and has no enzyme-inducing effect on the pill.
Step 4: Only an inducer threatens contraceptive cover, so the inhibitors and disulfiram are eliminated.
\[\boxed{\text{Griseofulvin}}\]
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