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methsuximide (Celontin, Kapseal)

Tradename: Celontin, Kapseals. Methsuximide was introduced in 1956 for treatment of absence seizures. Ethosuximide subsequently proved more effective [1]. Indications: 1) absence (petit mal) seizures 2) adjunctive therapy for refractory complex-partial seizures Dosage: 1) adults: start 300 mg PO QD for 1st week 2) may increase by 300 mg/day at weekly intervals up to 1.2 g/day divided BID-QID Tabs: 150 & 300 mg. Pharmacokinetics: 1) metabolized in liver to active metabolite N-desmethyl- methsuximide 2) t1/2 of 2-4 hours 3) t1/2 of N-desmethylmethsuximide is 28-36 hours Monitor: - liver function tests periodically [6] Adverse effects: 1) common (> 10%) - Stevens-Johnson syndrome, lupus-like syndrome, anorexia, ataxia, dizziness, drowsiness, hiccups, headache, nausea/vomiting, weight loss 2) less common (1-10%) - aggressiveness, depression, nightmares, weakness, lethargy 3) uncommon (< 1%) - agranulocytosis, leukopenia, aplastic anemia, thrombocytopenia, pancytopenia, paranoid psychosis, urticaria, exfoliative dermatitis Drug interactions: 1) increases phenytoin level 2) enhances conversion of primidone to phenobarbital 3) agents which may increase methsuximide metabolism a) carbamazepine b) phenobarbital c) phenytoin d) primidone 4) valproic acid may increase or decrease methsuximide levels Laboratory: 1) specimen: serum 2) methods: HPLC, GLC

Interactions

drug interactions drug adverse effects of anticonvulsants monitor with anticonvulsants

Related

methsuximide in serum/plasma

General

anticonvulsant succinimide

Properties

COMPARTMENT: mitochondrial matrix MISC-INFO: elimination route LIVER KIDNEY 1/2life 2-4 HOURS 30-50 HOURS therapeutic-range 10-40 NG/ML toxic-range >40 UG/ML protein-binding <5% pregnancy-category C safety in lactation ?

Database Correlations

PUBCHEM cid=6476

References

  1. The Pharmacological Basis of Therapeutics, 8th ed. Gilman et al, eds. Permagon Press/McGraw Hill pg 450
  2. The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996
  3. Harrison's Principles of Internal Medicine, 13th ed. Companion Handbook. Isselbacher et al (eds), McGraw-Hill Inc. NY, 1995, pg 701
  4. Kaiser Permanente Northern California Regional Drug Formulary, 1998
  5. Clinical Guide to Laboratory Tests, NW Tietz (ed) 3rd ed, WB Saunders, Philadelpha 1995
  6. Prescriber's Letter 17(7): 2010 Recommended Lab Monitoring for Common Medications Liver Function Test Scheduling Detail-Document#: 260704 (subscription needed) http://www.prescribersletter.com