Side effects of Phenytoin do not include:

 # Side effects of Phenytoin do not include:
 A. Osteomalacia
B. Gum hypertrophy
C. Folate deficiency
D. Blindness

The correct answer is D. Blindness. 

Adverse effects:  After prolonged use numerous side effects are produced at therapeutic plasma concentration; others occur as a manifestation of toxicity due to overdose.

At therapeutic levels
• Gum hypertrophy is common (20% incidence), especially in younger patients. It is due to the overgrowth of gingival collagen fibers. This can be minimized by maintaining oral hygiene.
• Hirsutism, coarsening of facial features (troublesome in young girls), acne.
• Hypersensitivity reactions are—rashes, DLE, and lymphadenopathy; neutropenia is rare but requires discontinuation of therapy.
• Megaloblastic anemia: Phenytoin decreases folate absorption and increases its excretion.
• Osteomalacia: Phenytoin interferes with metabolic activation of vit D and with calcium
• It can inhibit insulin release and cause hyperglycemia.
• Used during pregnancy, phenytoin can produce ‘fetal hydantoin syndrome’ (hypoplastic phalanges, cleft palate, hare lip, microcephaly), which is probably caused by its areneoxide metabolite.

Reference: Essentials of medical pharmacology, KD Tripathi.

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