A hypertensive patient with Type II diabetes is taking multiple medications. Which of the following medications is known to cause gingival hyperplasia?

Phenytoin (Dilantin), an anticonvulsant, is one of the three classic drug-induced causes of gingival hyperplasia (overgrowth), along with cyclosporine (immunosuppressant) and calcium channel blockers (such as nifedipine, amlodipine). Approximately 50% of patients on phenytoin develop gingival overgrowth. The mechanism involves altered fibroblast function with increased collagen synthesis. Metformin (for Type 2 diabetes), aspirin (antiplatelet), and hydrochlorothiazide (diuretic for hypertension) do not cause gingival hyperplasia. Good oral hygiene reduces but does not eliminate drug-induced gingival overgrowth.