TORONTO — Scientists have developed a one-two chemical punch that might help smokers kick the habit by spoiling the pleasures of cigarettes.

The combination consists of a nicotine patch plus another substance that blocks nicotine’s effects. Small, preliminary studies suggest that might work better than a regular patch.

The idea is to rob smoking of its rewards, such as the taste of tobacco and the tranquilizing and alertness-inducing effects of nicotine.

“We have the prospect of ruining the enjoyment of a cigarette,” said psychologist Jed Rose.

Rose is chief of the nicotine research laboratory at the Department of Veterans Affairs Medical Center in Durham, N.C., and a professor in psychiatry at Duke University Medical Center in Durham. He discussed the research Tuesday at a meeting of the American Psychological Association.

Harry Lando, a psychologist who studies smoking cessation at the University of Minnesota in Minneapolis, noted the work is preliminary but said, “I think it is very promising.”

Nicotine produces its effects by binding to certain sites on brain cells called receptors. This triggers the pleasurable but addicting effects.

To interrupt that, Rose has been working with mecamylamine, which was used decades ago as a blood pressure drug. Like nicotine, mecamylamine also binds to the receptors, but in a way that blocks nicotine’s effects. Separately, the drug also alters the taste of cigarettes and makes them less enjoyable, Rose said.

When mecamylamine (pronounced MEH-kuh-MIL-LUH-meen) is used by itself, it can cause drowsiness and dizziness, and by blocking cigarettes’ effect, can also make smokers crave nicotine. When mecamylamine is taken along with nicotine, these drawbacks are greatly reduced.

So the idea is to use the two drugs together. Nicotine from a patch turns on some brain receptors and mecamylamine blocks others. That way, the constant level of nicotine quells craving, while the mecamylamine blocks the reward from cigarettes.

A small study of 48 smokers found that those who took mecamylamine capsules and also used a nicotine patch before and after their planned date to quit smoking did better than those who got standard nicotine-patch treatment.

Six months after the quitting date, the combined group had an abstinence rate of 40 percent vs. about 15 percent for the patch-only group, Rose said. The results were similar at one year.

In a follow-up study to be published later this year, 80 smokers were split into four groups. For the four weeks before their stop-smoking date, one group went on a nicotine patch and took mecamylamine capsules twice a day, one group used just the patch, one group used just the capsules, and one group took placebo capsules with no patch.

After the quitting date, all the smokers took capsules and used the patch for six weeks. Then they stopped taking the capsules and weaned themselves off the patch over two weeks.

Six months after the quitting date, researchers checked to see who did best at avoiding even one cigarette.

Forty percent of the group that had both the patch and the capsules before the quitting date met that goal. The three other groups had success rates ranging from 10 percent to 20 percent.

The capsule-plus-patch group also showed significantly less craving and significantly fewer cigarettes smoked than the three other groups.