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 CCB’s are added to chronic carbamazepine therapy; enzyme induction by carbamazepine can reduce the bioavailability of CCB’s that undergo extensive 1^st-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