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Carbamazine

Commonly used agent for the treatment of epilepsy and trigeminal neuralgia and bipolar disorder.

Trade name Tegretol.

Used as well for attention-deficit hyperactivity disorder (ADHD), schizophrenia, phantom limb syndrome, extreme pain, post-traumatic stress disorder, and as a mood stabilizer in preganancy.

It induces the expression of the hepatic microsomal enzyme system CYP3A4, which metabolizes carbamazepine itself.

Carbamazine stabilizes the inactivated state of sodium channels, which are the molecular sites that allow neurons to generte action potentials, thereby making brain cells less excitable.

Potentiates GABA receptors made up of alpha1, beta2, gamma2 subunits.

Very high potential for drug interactions, and when administrated with phenobarbital, phenytoin, or primidone are associated with lower serm levels.

Is a CYP450 inducer, and may increase clearance of many drugs, decreasing their blood levels and includes: warfarin, phenytoin, theophylline, and valproic acid.

Drugs that decrease the metabolism of carbamazepine and increase its levels include erythromycin, cimetidine, propoxyphene, and calcium channel blockers.

Carbamazepine increases the metabolism of the hormones in birth control pills and can reduce their effectiveness.

Valproic acid inhibits microsomal epoxide hydrolase, the enzyme responsible for the breakdown of carbamazepine.

Grapefruit juice raises the bioavailability of carbamazepine by inhibiting CYP3A4 enzymes in the gut wall and in the liver.

Adverse effects include drowsiness, headaches, nausea, migraines, cardiac arrhythmias, impaired vision, thrombocytopenia, neutropenia, hyponatremmia and impaired motor coordination.

Associated with decreased alcohol tolerance, and may exacerbate hypothyroidism.

Carbamazepine increases the risk of developing lupus by 1.88 and may cause SIADH.

Associated with EEG slowing and cell apoptosis.

Stevens Johnson syndrome and toxic epidermal necrolysis are more common in patients with a particular human leukocyte antigen (HLA) allele, HLA-B*1502, that occurs almost exclusively in patients in Asia, including South Asian Indians.

In Europe a large proportion of dermatologic sensitivity is associated with HLA-B58, and HLA-B3101

A small number of patients can experience hypersensitivity reactions with substantial morbidity and mortality.

The mildest form of hypersensitivity is maculopapular exanthema occurring in 5 to 10% of treated patients of European ancestry.

Severe hypersensitivity reactions can be associated with mortality of up to 10% and includes fever, rash, eosinophilia, hepatitis and nephritis.

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