Carbamazepine Tablets

Mechanism

Carbamazepine is an anticonvulsant and mood stabilizer used in the treatment of epilepsy, trigeminal neuralgia, bipolar disorder, and neuropathic pain. It works by stabilizing hyperexcited nerve membranes and reducing abnormal electrical activity in the brain.

Pharmacokinetics

• Absorption: Slow and variable after oral administration.
• Peak Plasma Concentration: 4–8 hours.
• Protein Binding: ~70–80%.
• Metabolism: Extensively metabolized in the liver (CYP3A4).
• Excretion: Metabolites excreted via urine.
• Half-life: Initially 25–65 hours, reduced to 12–17 hours with chronic use due to autoinduction.

Side Effects

• Drowsiness, dizziness
• Nausea, vomiting
• Diplopia (double vision)
• Rare: Aplastic anemia, Stevens-Johnson syndrome, hyponatremia

Contraindication

• History of bone marrow depression
• Hypersensitivity to carbamazepine or tricyclic antidepressants
• Concomitant use with MAO inhibitors

Interaction

• Induces CYP3A4 → reduces effectiveness of oral contraceptives, warfarin, etc.
• Interacts with other antiepileptics (phenytoin, valproate, lamotrigine)
• Alcohol increases CNS depression

Warning and Precautions

• Use under medical supervision only
• Monitor blood counts regularly
• Monitor liver function and electrolytes
• Genetic screening for HLA-B*1502 allele in Asian patients (risk of severe skin reactions)