Methsuximide
CELONTIN
What it isSuccinimide T-type calcium channel blocker; absence seizures refractory to ethosuximide.
Why this oneIt penetrates better than ethosuximide and has some activity in focal seizures.
What limits itBlood dyscrasias require counts. More CNS toxicity than ethosuximide; it inhibits CYP2C19.
FDA-approved for
- refractory absence seizures (1957)
Off-label
- refractory focal and myoclonic seizures
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Absence (petit mal) seizures | adult/peds | 300 mg/day for first week | up to 1.2 g/day | 1.2 g/day |
Titration May increase at weekly intervals by 300 mg/day (over the 3 weeks following the first week)
Renal Undefined
Hepatic Undefined
Instructions
- Individualize to lowest dose controlling seizures; may combine with other anticonvulsants
- Do not discontinue abruptly (risk of precipitating status epilepticus)
Contraindications
- History of hypersensitivity to succinimides
Cautions
- Blood dyscrasias (leukopenia, pancytopenia, bone marrow suppression)
- Stevens-Johnson syndrome
- Psychiatric effects incl. depression, psychosis, suicidal behavior
- Do not discontinue abruptly
Adverse reactions
- Drowsiness, ataxia, dizziness (most frequent)
- Nausea/vomiting, anorexia, GI upset, weight loss
- Headache, blurred vision, photophobia
- Confusion, irritability, insomnia
- Rash, urticaria
Pregnancy Anticonvulsants associated with elevated incidence of birth defects; do not discontinue in patients where used to prevent major seizures
Lactation Undefined
NO BOXED WARNINGS
Principal riskBlood dyscrasias; more CNS toxicity than ethosuximide
Cost, est. cash$10–$500/month
Generic entry2023
Classes and tags
Clinical profile
Legacy pregnancy categoryC
Defining liabilitySedation, dizziness and agent-specific rash, behavioral, hepatic, hematologic or teratogenic toxicity.
Mechanism of action: Methsuximide ballicule
