Psoriasis Drug Still Looks Good for Quitting Smoking
July 28, 2000 -- In March this year, WebMD reported that an old drug had a new trick. Oxsoralen (methoxsalen), a treatment for psoriasis, was found in a small preliminary study to help smokers quit the habit.
Now, the investigators have furthered their research to show that additional research shows that smokers treated with low doses of Oxsoralen, combined with oral nicotine supplements, do indeed smoke fewer cigarettes.
In addition, a recent CDC report showed that every time a new product to help people quit smoking becomes available, the public's attempts to quit increase. So, the discovery that this drug could increase the effectiveness of nicotine patches or gum and enhance the use of simple oral nicotine supplements may prompt even more people to kick the habit.
Frank J. Vocci, PhD, director of treatment research and development at the National Institute on Drug Abuse (NIDA), tells WebMD, "We are very encouraged by [the] findings, and we have encouraged [the researcher] to follow up on this possible use of [Oxsoralen]." NIDA is providing part of the funding for future studies.
The University of Toronto research, conducted by Edward M. Sellers, MD, PhD, and colleagues at the university, appears in a recent issue of the journal Clinical Pharmacology and Therapeutics.
"Our main finding in the first study was that [Oxsoralen] at either 30 mg or 10 mg plus nicotine slows nicotine metabolism, increases blood nicotine concentrations, and reduces the patients' desire to smoke," says Rachel F. Tyndale, PhD, who conducted the studies with Sellers. Tyndale is associate professor of pharmacology at the University of Toronto's Center for Addictions and Mental Health in Toronto.
The second study showed that patients given the Oxsoralen/nicotine combination smoked fewer cigarettes, waited longer between cigarettes, and took fewer and/or shallower puffs per cigarette. The result was a nearly 50% reduction in smoke exposure.
Tyndale tells WebMD that tobacco-dependent smokers regulate their blood nicotine levels within a relatively narrow range to avoid concentrations that are too high or those that are low enough to cause symptoms of withdrawal. This is done by smoking more or fewer cigarettes, and by smoking faster or slower. Nicotine levels drop as nicotine is metabolized, but Oxsoralen blocks the enzyme that metabolizes nicotine, so smokers feel like they have high enough levels in their blood and don't smoke.
Blocking the enzyme might allow the use of nicotine pills rather than the nicotine patches, gums, or inhalers that are currently being used. Absorption of nicotine when taken orally is very small, so this has prevented the development of effective oral treatments. The Toronto researchers hope that Oxsoralen might increase the anount of nicotine in the body when it is taken orally, enough to make it an option for nicotine replacement therapy.