Researchers may have figured out how a drug called methoxsalen may help smokers quit smoking.

Methoxsalen blocks nicotine breakdown, write Jason Yano, PhD, and colleagues in Nature Structural & Molecular Biology. With nicotine intact, smokers may not crave cigarettes as much.

Methoxsalen also appears to block cancer-causing chemicals in tobacco from breaking down into even more harmful components, write the researchers.

The findings could lead to new quit-smoking medicines, writes Yano. He works in the molecular and experimental medicine department of the Scripps Research Institute in La Jolla, Calif.

Read WebMD's "Smoking Cigarettes Affects Brain Like Heroin"

About Methoxsalen

Methoxsalen's brand names include Oxsoralen, Oxsoralen-Ultra, Uvadex, 8-MOP, and, in Canada, Ultra MOP.

Methoxsalen is in a group of drugs called psoralens. It is used along with ultraviolet light to treat the skin conditions psoriasis and vitiligo, as well as a type of lymphoma called mycosis fungoides.

Read WebMD's "Quitting Smoking? Don’t Gain Weight"

Side Effects

Methoxsalen is a prescription drug that requires close medical supervision. It was not originally designed to help people quit smoking.

Methoxsalen's side effects include sensitivity to light, skin cancer, premature skin aging, and cataracts. Being exposed to sun while taking methoxsalen can lead to serious burns.

The drug is also not recommended for pregnant patients. It's not known if the drug can be passed through breast milk, so women who breastfeed should discuss the drug's risks with their doctor.

Methoxsalen may react with certain foods (such as carrots, celery, figs, limes, mustard, and parsley). Those foods should be avoided while taking methoxsalen.

Read WebMD's "CDC: Smoking Rates Continue to Drop"

Drug's Effects on Nicotine

How does methoxsalen affect nicotine and tobacco? The drug targets a protein called CYP2A6, which breaks down nicotine and tobacco's cancer-causing chemicals, write the researchers.

Yano and colleagues aren't recommending methoxsalen to smokers. They didn't test the drug on smokers who wanted to kick the cigarette habit. Instead, Yano's team wanted to figure out how methoxsalen affected CYP2A6.

Methoxsalen's structure "should aid the design of inhibitors to reduce smoking and tobacco-related cancers," write the researchers.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Yano, J. Nature Structural & Molecular Biology, advance online edition Aug. 7, 2005. News release, Nature Research Journals. Medline Plus, "Methoxsalen (Systemic)."