CARBAMAZEPINE

 

Introduction:  Closely related to imipramine and other antidepressants, carbamazepine is a tricyclic compound effective in treatment of bipolar depression.  It was initially marketed for the treatment of trigeminal neuralgia but has proved useful for epilepsy as well.

Molecular structure:  Although not obvious from a two-dimensional representation of its structure, carbamazepine has many similarities to phenytoin.  The ureide moiety (–N–CO–NH 2) in the heterocyclic ring of most antiseizure drugs is also present in carbamazepine. Three dimensional structural studies indicate that its spatial conformation is similar to that of phenytoin.

Mechanism of Action:  The mechanism of action of carbamazepine appears to be similar to that of phenytoin. Like phenytoin, carbamazepine shows activity against maximal electroshock seizures. Carbamazepine, like phenytoin, blocks Na⁺ channels at therapeutic concentrations and inhibits high-frequency repetitive firing in neurons in culture.  It also acts presynaptically to decrease synaptic transmission.  Potentiation of a voltage-gated K⁺  current has also been described. These effects probably account for the anticonvulsant action of carbamazepine. Binding studies show that carbamazepine interacts with adenosine receptors, but the functional significance of this observation is not known.

Clinical Uses:  Although carbamazepine has long been considered a drug of choice for both partial seizures and generalized tonic-clonic seizures, some of the newer antiseizure drugs are beginning to displace it from this role. Carbamazepine is not sedative in its usual therapeutic range. The drug is also very effective in some patients with trigeminal neuralgia, although older patients may tolerate higher doses poorly, with ataxia and unsteadiness. Carbamazepine is also useful for controlling mania in some patients with bipolar disorder.

RELATED;

1.  EPILEPSY

2.  PHARMACOLOGY AND THERAPEUTICS

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