Narcolepsy drug might lead to dependence through dopamine

Summarized by Susan Aldridge, PhD, medical journalist
March 27, 2009

Summary

Modafinil is a drug used to beat narcolepsy, or excessive sleepiness. Not much is known about how it works, however. A new study shows its blockage of the dopamine transporter in the brain, which suggests it could be addictive to certain patients.

Introduction

Narcolepsy is a neurological condition which leads to excessive sleepiness. One drug to treat it is modafinil, which is already used in sleep disorders and attention-deficit hyperactivity disorder (ADHD). Modafinil is a stimulant so it might have some potential for attention and abuse. But not much is known about how it acts upon the brain.

What was done

The effect of modafinil on the brains of ten healthy men aged 23-46 years was studied by researchers at the National Institute on Alcohol Abuse and Alcoholism. The men were given either the dose of modafinil used in narcolepsy, or that used in ADHD, or a placebo. Then the impact of the drug upon dopamine and the dopamine transporter were measured by positron emission tomography, an imaging technique that is used to monitor the activity of the brain.

What was found

Modafinil increase dopamine levels in the brain and also blocked the dopamine receptors. It also increased dopamine levels in the nucleus accumbens, the part of the brain that is linked to drug abuse.

What this study means

Modafinil was developed as a stimulant drug that would not affect the dopamine system of the brain. This study suggests, however, that the drug does indeed boost dopamine, especially in the area linked to drug abuse. Therefore, those on modafinil should be aware of the possibility of dependence and addiction.

Source

• Effects of modafinil on dopamine and dopamine transporters in the male human brain ND. Volkow, JS. Fowler,  et al, Journal of the American Medical Association, March 18 2009, vol. 301, pp. 1148--1154