Carbamazepine (Tegretol, Carbatrol, Atretol)

Category:

  • Miscellaneous

Description:

  • Anticonvulsant; antineuralgic; antimanic; antipsychotic

Indications:

  • Tonic-clonic, complex-partial, mixed seizures

  • Trigeminal neuralgia

Contraindications:

  • Hypersensitivity to tricyclic antidepressants, bone marrow depression, concomitant use of MAO inhibitor

Precautions:

  • Pregnancy category C

  • Glaucoma, hepatic disease, renal disease, cardiac disease, psychosis

  • Child < age 6

Adverse Reactions (Side Effects):

  • CNS: ataxia, confusion, dizziness, drowsiness, hallucinations, headache, parlaysis

  • CV: CHF, hypertension, hypotension, aggravation of coronary artery disease

  • EENT: bBlurred vision, conjunctivitis, diplopia, dry mouth, nystagmus, tinnitis

  • GI: abdominal pain, anorexia, constipation, diarrhea, glossitis, hepatitis, nausea

  • HEME: agranulocytosis, aplastic anemia, eosinophilia, leukocytosis, neutropenia, thrombocytopenia

  • RESP: fever, dyspnea, pneumonitis

  • SKIN: rash, Stevens-Johnson syndrome, urticaria  

Dosage:

Administered orally (tablet, chewable tablet, suspension)

  • Adult Dose:

    • Seizures: 

      • PO 200mg twice daily

      • may increase by 200mg daily in divided doses every 6-8 hours

      • maintenance 800-1200mg daily

      • maximum dose 1200mg per day

    • Trigeminal neuralgia: 

      • PO 100mg twice daily

      • may increase 100mg every 12 hours until pain subsides

      • not to exceed 1.2 grams daily

      • maintenance 200-400mg twice daily

    • Antidiuretic: 

      • PO 300-600mg daily as sole therapy

      • 200-400mg daily if concurrent with other antidiuretic agents

    • Antipsychotic: 

      • PO 200-400 mg/day divided 3-4 times per day

      • max 1600mg daily

  • Child < age 12:  

    • Seizures: 

      • PO 10-20 mg/kg/day in 2-3 divided doses

Drug Interactions:  

  • Calcium channel blockers (CCB): Verapamil and diltiazem reduce the metabolism of carbamazepine leading to increased carbamazepine toxicity when these CCBs are added to chronic carbamazepine therapy; enzyme induction by carbamazepine can reduce the bioavailability of CCBs that undergo extensive 1st-pass hepatic clearance, like felodipine (94% reduction)

  • Propoxyphene: reduces carbamazepine levels

  • Valproic acid: can increase, decrease, or have no effect on carbamazepine; carbamazepine decreases valproic acid levels

  • Theophylline: carbamazepine reduces levels and therapeutic effect

  • Omeprazole: may increase carbamazepine concentrations

  • Oral anticoagulants: decreased prothrombin time

  • Phenytoin: concurrent use reduces serum concentrations of both

  • Metronidazole and isoniazid: increases carbamazepine concentrations with toxicity

  • Ethinyl estradiol, oral contraceptives: carbamazepine-induced metabolic induction may lead to menstrual irregularities and unplanned pregnancies

  • Doxycycline: carbamazepine reduces doxycycline levels and antibiotic effects

  • Erythromycin and clarithromycin: increased carbamazepine levels

  • Corticosteroids: carbamazepine reduces levels and therapeutic effects

  • Cimetadine: Transient (1 week) increases in carbamazepine levels



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