Methsuximide

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Contents 1 Introduction 2 Indications 3 Dosage 4 Pharmacokinetics 5 Monitor 6 Adverse-effects 7 Drug-interactions 8 Laboratory 9 More General Terms 10 Internet Database 11 References

Introduction

• Tradename: Celontin, Kapseals. Methsuximide was introduced in 1956 for treatment of absence seizures. Ethosuximide subsequently proved more effective [1].

Indications

• absence ( petit mal) seizures
• adjunctive therapy for refractory complex-partial seizures

Dosage

• adults: start 300 mg PO QD for 1st week
• may increase by 300 mg/day at weekly intervals up to 1.2 g/day divided BID- QID

• Tabs: 150 & 300 mg.

Pharmacokinetics

• metabolized in liver to active metabolite N-desmethyl- methsuximide
• t1/2 of 2-4 hours
• t1/2 of N-desmethylmethsuximide is 28-36 hours
  

• elimination via liver
• elimination via kidney
• 1/2life = 2-4 hours
• 1/2life = 30-50 hours N-desmethyl methsuximide
• protein binding = <5 % small

Monitor

• liver function tests periodically [6]
  
• monitor with anticonvulsants

Adverse-effects

• common (> 10%)

• Stevens-Johnson syndrome, lupus-like syndrome, anorexia, ataxia, dizziness, drowsiness, hiccups, headache, nausea/vomiting, weight loss

• less common (1-10%)

• aggressiveness, depression, nightmares, weakness, tiredness

• uncommon (< 1%)

• agranulocytosis, leukopenia, aplastic anemia, thrombocytopenia, pancytopenia, paranoid psychosis, urticaria, exfoliative dermatitis

• other

• ataxia
• lethargy
  
• drug adverse effects of anticonvulsants

Drug-interactions

• increases phenytoin level
• enhances conversion of primidone to phenobarbital
• agents which may increase methsuximide metabolism

• carbamazepine
• phenobarbital
• phenytoin
• primidone

• valproic acid may increase or decrease methsuximide levels

Laboratory

• specimen: serum
• methods: HPLC, GLC

More General Terms

• succinimide
• anticonvulsant

Internet Database

PubChem: 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#: [1] (subscription needed) [2]

methsuximide (Celontin, Kapseal)