On chronic treatment with a drug, a patient presents with gingival hyperplasia and facial hirsutism. The drug most likely to cause these side effects is :
**Core Concept**
The patient's presentation of gingival hyperplasia and facial hirsutism is likely due to an increase in androgenic activity, leading to an abnormal growth of hair and gingival tissue.
**Why the Correct Answer is Right**
This side effect profile is characteristic of drugs that inhibit the enzyme _P450 3A4_, which is involved in the metabolism of certain steroids, including dihydrotestosterone (DHT). The drug that most likely causes these side effects is **Phenytoin**, which is a well-known inducer of _P450 3A4_. By inducing this enzyme, Phenytoin increases the levels of free testosterone and DHT, leading to increased androgenic activity. This results in excessive hair growth (hirsutism) and abnormal growth of gingival tissue (gingival hyperplasia).
**Why Each Wrong Option is Incorrect**
* **Option A:** Not specified. This option does not provide a relevant drug that could cause the described side effects.
* **Option B:** Not specified. This option does not provide a relevant drug that could cause the described side effects.
* **Option C:** Not specified. This option does not provide a relevant drug that could cause the described side effects.
**Clinical Pearl / High-Yield Fact**
Phenytoin-induced gingival hyperplasia and hirsutism are classic side effects of this medication, and clinicians should be aware of these potential complications when prescribing Phenytoin to patients.
**Correct Answer: C. Phenytoin**