Phenytoin can cause a gingival overgrowth as a notable adverse effect requiring monitoring.

• A. Rash including Stevens-Johnson syndrome.
• B. Gingival hyperplasia.
• C. Weight gain.
• D. Photosensitivity.

Answer: (B)

Phenytoin commonly causes gingival hyperplasia, a noticeable overgrowth of gum tissue that requires monitoring. This occurs because the drug stimulates gingival fibroblasts and increases extracellular matrix production in the gums while slowing its breakdown, leading to thickened, enlarged gingiva. The condition often develops after months of therapy and can be worse with poor oral hygiene, so regular dental care and good oral hygiene are important parts of management. In some cases, dose adjustments or switching anticonvulsants may be considered if the overgrowth is severe.

Rash, including Stevens-Johnson syndrome, can occur with anticonvulsants but is not the most characteristic or routinely monitored adverse effect for phenytoin. Weight gain is more commonly associated with other medications, and photosensitivity is not a hallmark adverse effect of phenytoin.