An inexpensive drug commonly used to treat patients with type 2 diabetes may block symptoms of nicotine withdrawal, at least in rodents.
After researchers exposed laboratory mice to a two-week regimen of nicotine they displayed no withdrawal symptoms when they took the drug, called metformin, the researchers report in the Proceedings of the National Academy of Sciences.
Cigarette smoking is the leading cause of preventable illness and death in the United States, implicated in more than 500,000 deaths each year, according to public health officials. There are three medicines approved by the US Food and Drug Administration to help people break addictions to nicotine.
Still, smoking cessation rates remain low—at about 15 percent—even though some studies say up to 70 percent of smokers want to quit.
The three therapies now available are nicotine replacement, an antidepressant, and a medication aimed at reducing the cravings for and pleasurable effects of cigarettes. None directly treats nicotine withdrawal symptoms, says Sangwon Kim of the Johns Hopkins University School of Medicine’s Division of Endocrinology, Diabetes, and Metabolism.
Based on previous studies that identified how nicotine affects brain chemistry, Kim and his colleagues hypothesized that metformin might eliminate anxiety, irritability, and other withdrawal symptoms.
The research team, from both Johns Hopkins and the University of Pennsylvania, focused on activating an enzyme known as AMP-activated protein kinase. Among other roles, AMPK stimulates the breakdown of glucose for energy. Kim and his colleagues discovered that the AMPK pathway activates in mammals following chronic nicotine use, but is repressed during nicotine withdrawal. They set out to find whether AMPK, stimulated by metformin, could lessen or even eliminate the symptoms of nicotine withdrawal.
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“This is the first-ever study to examine AMPK’s relation to nicotine dependence,” Kim says.
Metformin suppresses liver glucose production. With proper dosages, however, the researchers thought it might treat nicotine withdrawal symptoms without throwing blood glucose out of balance.
The researchers found that nicotine-treated mice given metformin displayed none of the anxiety or other negative effects of withdrawal. Metformin, in fact, completely prevented anxious behaviors caused by nicotine withdrawal at doses that had no effect on body weight, food consumption, or glucose levels.
Kim says the research suggests that metformin, because of its long-term record of safety and relative lack of side effects, has “real potential” as a smoking cessation aid if clinical trials in humans confirm the findings in mice.
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The National Institutes of Health funded the study.
Source: Johns Hopkins University
