A succinimide anticonvulsant, used mainly in absence seizures.

Generic availability.

Oral agent with 93% bioavailability.

Hepatic metabolism by CYP3A4, CYP2E1 enzymes.

Half-life of 53 hours.

Excretion by renal mechanism of 20%.

The first choice drug for treating absence seizures.

Therapeutic Range: 40-100 µg/mL, with potentially toxic serum concentration: >100 µg/mL.

Available as capsules or syrup.

Affects neuronal excitability including blockage of T-type Ca2+ channels, and may effect drugs of other classes of ion channel.

Subsequent experiments on recombinant T-type channels in cell lines demonstrated conclusively that ethosuximide

Blocks all T-type Ca2+ channel isoforms.

The decrease in Na+ current is responsible for the anti-absence properties.

Valproates can either decrease or increase the levels of ethosuximide.

Combinations of valproates and ethosuximide have a greater effect than either drug alone.

It may elevate serum phenytoin levels.

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