A patient on phenytoin develops gingival hyperplasia. The most accepted cellular mechanism is:

• A Direct stimulation of fibroblast proliferation mediated by calcium channel-independent pathways
• B Increased expression of folic acid-dependent collagen synthesis genes
• C Competitive antagonism of testosterone receptors in gingival cells
• D Phenytoin's blockade of voltage-gated calcium channels in gingival fibroblasts impairing collagen phagocytosis ✓

Explanation

Phenytoin blocks voltage-gated calcium channels in gingival fibroblasts, impairing their ability to phagocytose and degrade collagen. This leads to collagen accumulation and gingival overgrowth. Poor oral hygiene worsens the condition. The same fibroblast mechanism occurs with other calcium channel blockers (e.g., nifedipine) and cyclosporine, which also cause gingival hyperplasia. Good oral hygiene and professional dental cleaning can reduce its severity.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.