Which of the following is NOT listed as an adverse reaction to Dilantin?

• A. Gingival Hyperplasia
• B. Hypokalemia
• C. Ataxia
• D. Decreased Vitamin D Absorption

Answer: (B)

Phenytoin (Dilantin) adverse effects commonly involve gum overgrowth, coordination problems, and bone health changes from enzyme induction. Among the options, hypokalemia is not a typical adverse reaction to phenytoin. Gingival hyperplasia is a well-known effect caused by increased gingival fibroblast activity and collagen production, so dental hygiene and monitoring are often recommended. Ataxia reflects CNS toxicity and is a common side effect, especially during dose adjustments or at higher levels. Decreased vitamin D absorption occurs because phenytoin induces hepatic enzymes that increase vitamin D metabolism, leading to lower vitamin D levels and potential bone demineralization with long-term use. While electrolyte disturbances can occur in various contexts, hypokalemia is not listed as a standard adverse reaction to Dilantin.