What is a common adverse reaction associated with Phenytoin?

Phenytoin, an anticonvulsant medication often used to manage seizures, is associated with a variety of side effects, one of which is excessive hair growth, known as hirsutism. This adverse reaction occurs due to the effect of phenytoin on hair follicle activity and hormone levels, leading to increased hair growth in areas where men typically grow hair, as well as in women.

While some of the other choices listed may be associated with different medications or conditions, they are not commonly linked to phenytoin. For instance, hypoglycemia, or low blood sugar, is more frequently observed with certain diabetes medications rather than anticonvulsants. Pneumonia can occur in the general population but is not a direct side effect of phenytoin. Similarly, diarrhea can happen due to a variety of factors including other medications, dietary issues, or infections, but it is not a well-documented side effect of phenytoin. Understanding these specific interactions helps healthcare providers monitor patients for hirsutism and manage any cosmetic or psychological impacts it may have.