Question

Which of the following antiepileptic drugs is contraindicated for absence seizures in children?

• A. Ethosuximide
• B. Lamotrigine
• C. Phenytoin
• D. Valproic acid

Hint:

Absence Seizure Drug Rules: - Preferred: Ethosuximide (children), Valproic acid. - Aggravators Contraindicated: Phenytoin, Carbamazepine, Vigabatrin.

Answer 1

The Correct Option is C

Understanding the Concept: Absence seizures (petit mal) are characterized by brief, sudden lapses of consciousness, driven by synchronized $3\text{ Hz}$ spike-and-wave discharges generated by low-threshold T-type calcium channels in thalamocortical relay neurons.
• Ethosuximide: The first-line choice for pediatric absence seizures, as it selectively blocks these T-type calcium channels.
• Valproic Acid: A broad-spectrum antiepileptic that blocks T-type calcium channels along with sodium channels, making it highly effective for absence seizures.

Step 1: Evaluate the effect of Phenytoin on absence seizures.
Phenytoin functions primarily by prolonging the inactivated state of voltage-gated sodium channels. It lacks activity against T-type calcium channels and can paradoxically aggravate or increase the frequency of absence seizures. For this reason, it is strictly contraindicated in patients presenting with absence epilepsy.