Drug May Help Weight-Concerned Smokers Trying to Quit

The drug naltrexone might help reduce weight gain in smokers as they try to quit, according to a study by Yale School of Medicine researchers published this week in the Archives of Internal Medicine.

The researchers found that smokers who took a 25 mg dose of naltrexone in addition to the nicotine patch gained significantly less weight than those who did not take the drug. Over the six-week treatment period, those who took placebo gained 4.2 pounds while those who took the naltrexone gained 1.5 pounds on average.

 “These results show that naltrexone has promise when it comes to helping people reduce the weight gain so often associated with quitting smoking,” said Stephanie O’Malley, lead author of the study and principal investigator for the Transdisciplinary Tobacco Use Research Center (TTURC) at Yale. “This is an important finding because many smokers won’t even attempt to quit because they are concerned about gaining weight.”

Naltrexone works by blocking some of the reinforcing effects of endogenous opioids, which are part of the chemical system in the brain that creates a sense of reward and helps reduce pain. Substances such as sweet and rich foods, morphine, alcohol and smoking stimulate this system. The Food and Drug Administration originally approved naltrexone’s use for those who are trying to quit opiates, like heroin and morphine

The study included 400 patients who smoked at least one pack of cigarettes a day.  All patients were treated with a nicotine patch and were randomly assigned to receive placebo, 25 mg, 50 mg or 100 mg of naltrexone daily. Smoking behavior and weight were measured at weekly appointments and during a one-year follow-up.

Although the 25 mg dose reduced weight gain during treatment, it did not increase the number of smokers who were able to quit smoking. O’Malley is currently investigating the effect of 25 mg naltrexone in a subset of smokers who smoke, in part, to manage their weight. The reduction of post-cessation weight gain may translate into improved rates of smoking cessation, O’Malley said.

 “Many weight concerned smokers resume smoking in response to weight gain. If we can minimize weight gain, more people may be successful,” she said.

The study did find that a 100 mg dose of naltrexone improved the odds of quitting smoking in smokers who completed the treatment. O’Malley says this preliminary finding needs further investigation before this dose can be recommended for smoking cessation in clinical practice.

“Naltrexone hydrocholoride, an opiate antagonist, has the potential to promote smoking cessation and reduce weight gain based on the documented role of the endogenous opioid system in regulating these behaviors,”  the authors of the study said. “The results of this study provide support for further testing of the efficacy of the 100 mg dose for smoking cessation. In the meantime, the benefit of low-dose naltrexone on reducing weight gain may have immediate clinical utility for the subset of weight-concerned smokers.”

Yale University holds a patent for smoking cessation treatments using naltrexone and related compounds and is seeking a licensee.

For more information about TTURC, please see www.quitwithyale.org. The National Institute on Drug Abuse (NIDA), the National Institute on Alcohol Abuse and Alcoholism (NIAAA), the National Cancer Institute (NCI) and The Robert Wood Johnson Foundation, funds TTURC.

Archives of Internal Medicine 166: 667-674 (March 27, 2006)