**Core Concept**
Isotretinoin, a derivative of vitamin A, is a teratogenic medication used in the treatment of severe acne. Its use during pregnancy can lead to congenital anomalies and fetal malformations. To prevent such complications, it is crucial to manage isotretinoin therapy appropriately during pregnancy.

**Why the Correct Answer is Right**
Isotretinoin has a long half-life of approximately 18-20 hours, which allows it to remain in the body for an extended period. The drug's effects on the fetus can persist even after discontinuation. Therefore, it is essential to stop isotretinoin at least 3 months before conception to minimize the risk of teratogenic effects. This allows sufficient time for the drug to be eliminated from the body and reduces the likelihood of fetal exposure.

**Why Each Wrong Option is Incorrect**
**Option A:** Stopping isotretinoin 3 days before pregnancy is not sufficient, as the drug's half-life and prolonged elimination period make it necessary to discontinue therapy well in advance of conception.

**Option B:** Discontinuing isotretinoin 2 weeks before pregnancy is still not adequate, as the drug's effects can persist for several months after cessation.

**Option D:** Stopping isotretinoin 3 years before pregnancy is excessively cautious and not necessary, as the drug's teratogenic effects are most pronounced during the first trimester of pregnancy.

**Clinical Pearl / High-Yield Fact**
A key aspect of managing isotretinoin therapy is the use of two forms of birth control: a primary method (e.g., condoms, diaphragm) and a secondary method (e.g., oral contraceptives). This dual approach ensures that the patient is adequately protected against pregnancy while on isotretinoin.

✓ Correct Answer: C. 3 month