Iminostilbenes

Iminostilbenes

Carbamazepine is the most commonly used iminostilbene anti-convulsant. It effectively treats:

·                 partial and generalized tonic-clonic seizures

·                 mixed seizure types

·                 complex partial seizures (drug of choice).

Pharmacokinetics

Carbamazepine is absorbed slowly from the GI tract and is metab-olized in the liver by the cytochrome P-450 isoform 3A4 (CYP450) and is excreted in urine. Carbamazepine is distributed rapidly to all tissues; 75% to 90% is bound to plasma proteins. A small amount crosses the placenta, and some is secreted in breast milk. The half-life varies greatly.

Pharmacodynamics

Carbamazepine’s anticonvulsant effect is similar to that of pheny-toin. The drug’s anticonvulsant action can occur because of its ability to inhibit the spread of seizure activity or neuromuscular transmission in general

Pharmacotherapeutics

Carbamazepine is the drug of choice, in adults and children, for treating:

·                 generalized tonic-clonic seizures

·                 simple and complex partial seizures.

Carbamazepine may worsen absence or myoclonic seizures. However, it relieves pain when used to treat trigeminal neuralgia (tic douloureux, characterized by excruciating facial pain along the trigeminal nerve) and may be useful in treating selective psy-chiatric disorders.

Drug interactions

Carbamazepine can reduce the effects of several drugs, including haloperidol, bupropion, lamotrigine, tricyclic antidepressants, oral anticoagulants, hormonal contraceptives, doxycycline, felbamate, theophylline, protease inhibitors, antipsychotics, and valproic acid. Other drug interactions can also occur:

Increased carbamazepine levels and toxicity can occur with the use of cimetidine, danazol, diltiazem, erythromycin, isoniazid, se-lective serotonin reuptake inhibitors, propoxyphene, ketocona-zole, valproic acid, and verapamil.Lithium and carbamazepine taken together increase the risk of toxic neurologic effects.

Confusion alert!

§    Don’t confuse Tegretol (a brand name for carbamazepine) with Toradol (a brand name for ketorolac).

§    Carbamazepine levels may be decreased when taken with barbi-turates, felbamate, or phenytoin. (See Adverse reactions to carba-mazepine.)

§    The herbal remedy plantain may inhibit GI absorption of carba-mazepine.