• Metabolism: Hepatic. CYP3A4 is the primary isoform responsible for the formation of carbamazepine-10,11-epoxide. This metabolite is active and shown to be equipotent to carbamazepine as an anticonvulsant. Carbamazepine is more rapidly metabolized to the aforementioned metabolite in younger patients than in adults. It also undergoes glucuronidation via UGT2B7, however this finding has been disputed. Route of Elimination: 72% of the dose is in the urine while 28% is in the feces. Hydroxylated and conjugated metabolites are largely what was recovered in the urine. 3% of the dose is recovered as unchanged carbamazepine. Half Life: Initial half-life values range from 25-65 hours, decreasing to 12-17 hours on repeated doses.
• Uses/Sources: For the treatment of epilepsy and pain associated with true trigeminal neuralgia.
• Health Effects: May cause a potentially dangerous rash that may develop into Stevens Johnson syndrome, an extremely rare but potentially fatal skin disease.
• Symptoms: Mild ingestions cause vomiting, drowsiness, ataxia, slurred speech, nystagmus, dystonic reactions, and hallucinations. Severe intoxications may produce coma, seizures, respiratory depression, and hypotension
• Treatment: The prognosis in cases of severe poisoning is critically dependent upon prompt elimination of the drug, which may be achieved by inducing vomiting, irrigating the stomach, and by taking appropriate steps to diminish absorption. If these measures cannot be implemented without risk on the spot, the patient should be transferred at once to a hospital, while ensuring that vital functions are safeguarded. There is no specific antidote. (L1712)
• Route of Exposure: Oral. In clinical studies, carbamazepine suspension, conventional tablets, and extended-release tablets delivered equivalent amounts of drug to the systemic circulation. However, it has been observed that the suspension is somewhat faster absorbed. Furthermore, the extended-release tablet is slightly slower than the conventional tablet. The bioavailability of the extended-release tablet is 89%, compared to the suspension. Plasma levels of carbamazepine are variable. The time to peak concentration for the different formulations are as follows: Suspension = 1.5 hours; Conventional tablets = 4-5 hours; Extended-release tablets = 3-12 hours.

Carbamazepine inhibits sustained repetitive firing by blocking use-dependent sodium channels. Pain relief is believed to be associated with blockade of synaptic transmission in the trigeminal nucleus and seizure control with reduction of post-tetanic potentiation of synaptic transmission in the spinal cord. Carbamazepine also possesses anticholinergic, central antidiuretic, antiarrhythmic, muscle relaxant, antidepressant (possibly through blockade of norepinephrine release), sedative, and neuromuscular-blocking properties.