seizure is a side effect of
**Core Concept**
Seizure is a side effect of certain medications that affect neuronal excitability, particularly those altering the balance between excitatory and inhibitory neurotransmission. This is often due to the modulation of ion channels, neurotransmitter release, or synaptic plasticity.
**Why the Correct Answer is Right**
The correct answer is likely a medication that increases neuronal excitability by enhancing glutamatergic transmission, such as isoniazid, a first-line antitubercular agent. Isoniazid inhibits GABA transaminase, the enzyme responsible for GABA degradation, leading to increased GABA levels and subsequent enhancement of inhibitory neurotransmission. However, by also increasing the release of excitatory neurotransmitters like glutamate, isoniazid can induce seizures as a side effect.
**Why Each Wrong Option is Incorrect**
* **Option A:** This is incorrect because beta-blockers, such as propranolol, are generally used to manage anxiety or tremors and do not typically cause seizures as a side effect.
* **Option B:** This is incorrect because anticholinergic medications, such as atropine, primarily cause side effects like dry mouth, blurred vision, and constipation, but are not typically associated with seizures.
* **Option C:** This is incorrect because antihistamines, such as diphenhydramine, cause sedation, drowsiness, and dry mouth as side effects, but are not commonly associated with seizures.
**Clinical Pearl / High-Yield Fact**
Remember that medications affecting GABA and glutamate balance are more likely to cause seizures as a side effect. This is particularly relevant for antitubercular agents like isoniazid and certain anticonvulsants.
**Correct Answer: C. Isoniazid**