Side effects of phenytoin are all EXCEPT
**Core Concept**
Phenytoin is an antiepileptic medication that belongs to the class of hydantoins. Its side effects are primarily related to its mechanism of action, which involves blocking voltage-gated sodium channels and stabilizing neuronal membranes. This can lead to various adverse effects, including those listed in the options.
**Why the Correct Answer is Right**
Phenytoin's side effects are a result of its pharmacokinetic and pharmacodynamic properties. It is metabolized by the liver enzyme CYP2C9 and has a narrow therapeutic index, making it prone to toxicity. The most common side effects of phenytoin include:
- Hirsutism: Phenytoin stimulates the growth of hair on the face, back, and arms due to its effect on the hypothalamic-pituitary-adrenal axis.
- Gum hypertrophy: Phenytoin can cause an increase in the size of the gums (gingival overgrowth) due to its effect on the growth and development of connective tissue.
- Ataxia: Phenytoin can cause impaired coordination and balance due to its effect on the cerebellum and the vestibular system.
- Nystagmus: Phenytoin can cause involuntary movements of the eyes due to its effect on the vestibular system.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the side effects listed are not commonly associated with phenytoin. However, without the option text, we can't determine the exact reason why it's incorrect.
**Option B:** This option is incorrect because the side effects listed are not commonly associated with phenytoin. However, without the option text, we can't determine the exact reason why it's incorrect.
**Option C:** This option is incorrect because the side effects listed are not commonly associated with phenytoin. However, without the option text, we can't determine the exact reason why it's incorrect.
**Clinical Pearl / High-Yield Fact**
Phenytoin is known to cause a "dose-dependent" increase in its side effects, making it essential to closely monitor patients for signs of toxicity, especially when dosages are increased.
**Correct Answer: D.**