Pharm

Zonisamide

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Zonisamide, Zonegran

  • Indications
  1. Adjunctive management of Partial Seizures
  2. Add to primary antiepileptic regimens
    1. Carbamazepine
    2. Phenytoin
    3. Valproate
  3. Other potential uses currently being researched
    1. Myoclonic Seizures
    2. Infantile Spasm
    3. Atypical Absence Seizure
    4. Generalized Tonic Clonic Seizures
  • Pharmacology
  1. Weak carbonic anhydrase inhibitor
  2. Sulfonamide that blocks Sodium and Calcium channels
    1. Increases Dopaminergic transmission
    2. Increases serotonergic transmission
  3. Metabolized by CYP3A4
  4. Half-Life: 60 hours
  • Drug Interactions
  1. Increased Zonisamide clearance with CYP3A4 inducers
    1. Phenytoin
    2. Carbamazepine
    3. Phenobarbital
  2. Concurrent carbonic anhydrase inhibitor (Topamax)
    1. Increased Nephrolithiasis risk
  • Adverse effects
  1. Dizziness
  2. Ataxia
  3. Somnolence
  4. Nausea
  5. Anorexia
  6. Abdominal Pain
  7. Insomnia
  8. Impaired cognition
    1. Confusion
    2. Decreased concentration
    3. Speech problems
  9. Psychosis
  10. Nephrolithiasis
  11. Rash
  12. Stevens Johnson Syndrome
  13. Toxic Epidermal Necrolysis
  14. Childhood Adverse Effects
    1. Oligohydrosis
    2. Hyperthermia (and Heat Stroke)
  • Contraindications
  1. Sulfonamide Allergy
  2. Pregnancy (Teratogenic in animals)
  • Dosing
  • Adults
  1. Initial: 100 mg PO qd
  2. Increase: 100 mg every two weeks as needed
  3. Maximum: 600 mg/day divided qd-bid
  4. Caution: Increase more slowly in Renal Insufficiency
  • References
  1. Padgett (1997) Epilepsia 38(suppl 8):107 [PubMed]
  2. Schmidt (1993) Epilepsy Res 15:67 [PubMed]
  3. Wallace (1998) Epilepsy Res 29:147 [PubMed]
  4. Yagi (2000) Neurology 54(Suppl 3):A195 [PubMed]
  5. Yanai (1999) Brain Dev 21:157 [PubMed]
  6. (2000) Med Lett Drugs Ther 42(1089):93-4 [PubMed]