ABSTRACT
Methsuximide (MSM) was introduced in 1957 for the treatment of refractory absence seizures. It belongs to the succinimide family ethosuximide (ESM) and phensuximide, which shares a common heterocyclic ring. Phenyl group substitution at the 2C position counteracts experimentally induced maximal electroshock seizures, whereas alkyl group substitution at the 2C position counteracts experimentally induced pentylenetetrazol (PTZ) seizures. Methyl group substitution at the 5N position adds to the anti-pentylenetetrazol effect and the sedative activity of the molecule. MSM is readily absorbed and achieves peak plasma levels within 2 to 4 hours. It distributes evenly throughout the body and penetrates into the brain and fat tissue better than ESM. MSM interacts with other antiepileptic drugs (AEDs) and close monitoring of serum levels and an adjustment in dosage of concurrent AEDs may at times be necessary, especially if the patient begins to show signs of clinical toxicity. Common adverse effects of MSM include gastrointestinal disturbance, lethargy, somnolence, fatigue, and headaches.
