First-line therapy for absence seizures is which of the following?

• A. Gabapentin (Neurontin)
• B. Ethosuximide (Zarontin)
• C. Phenytoin (Dilantin)
• D. Carbamazepine (Tegretol)

Answer: (B)

Absence seizures are driven by abnormal thalamocortical oscillations that rely on T-type calcium channels. Ethosuximide directly reduces calcium currents through these T-type channels in the thalamus, which suppresses the spike-and-wave discharges that produce the brief lapses in consciousness. This targeted mechanism is why ethosuximide is the preferred first-line therapy for typical absence seizures.

The other agents listed aren’t first-line for this type of seizure because they either act mainly on sodium channels and are better suited for focal seizures, or they don’t effectively counter the thalamocortical rhythm involved in absence seizures. Ethosuximide’s specific action on T-type calcium channels makes it the best initial choice.