Study examines effects of AEDs on nicotine metabolite levels in smokers

UMDNJ-Robert Wood Johnson Medical School researchers have determined that carbamazepine and oxycarbamazepine, medications commonly used to treat neurologic and psychiatric conditions, increase nicotine metabolism in smokers. As nicotine metabolism increases, cravings for nicotine return more quickly which could lead to more frequent cigarette consumption among individuals who also take these medications.

The study examined the effects of three anti-epileptic drugs - carbamazepine, oxcarbazepine and valproic acid - on nicotine and nicotine metabolite levels in 149 smokers with schizophrenia and bipolar disorder.

"We believe this is the first report of either carbamazepine or oxcarbazepine causing a clinically significant interaction with nicotine metabolism," study author Jill M. Williams, M.D., an associate professor of psychiatry and director of the Division of Addiction Psychiatry at UMDNJ-Robert Wood Johnson Medical School, said.

Smoking is more prevalent in people with serious forms of mental illnesses, such as schizophrenia and bipolar disorder, than in the general population, explained Kunal K. Gandhi, M.B.B.S., M.P.H., an instructor of psychiatry at the UMDNJ-Robert Wood Johnson Medical School and study co-author.

"The effect of these medications may have serious implications on nicotine metabolism and smoking behavior," Williams added.

"Anti-epileptic drugs (AED) are of particular concern with respect to drug interactions because of their potential to induce many hepatic cytochrome P450 enzymes and increases nicotine metabolism," Williams explained. "We will need to do more studies to see if carbamazepine or oxycarbamazepine affect smoking behavior or intake of tobacco smoke from cigarettes in groups of smokers who may or may not have mental illness, but they could increase smoking as well as craving for nicotine."

AEDs are commonly used as adjunctive treatment for conditions other than epilepsy, including schizophrenia and bipolar disorder. This has implications for smokers using these medications and seeking smoking cessation treatment, Williams noted.

"Although the study was conducted in smokers with mental illness, it is unlikely that this effect was due to mental illness alone since we have found no difference in nicotine metabolite ratios in our other studies of smokers with mental illness not taking these drugs," Williams added.