Researches have found that Chantix, the popular Pfizer drug that helps people quit smoking, may instead give people heart attacks and other cardiovascular problems.

 Scientists in the UK and the US said this week that after looking at 14 clinical trials, the likelihood of developing serious heart problems resulting in hospitalization, disability or death was 72 percent higher in patients taking the drug compared with those taking a placebo.

The new study comes just over a week after the Food and Drug Administration reported a small but significant risk while using the drug.

All smokers who take Chantix are at risk for heart attack, stroke or other cardiovascular event, said study author Dr. Sonal Singh, an assistant professor of general internal medicine at the Johns Hopkins.

Our new research shifts the risk-benefit profile of varenicline, said Sonal Singh of Johns Hopkins University School of Medicine, who led the research and published it in the Canadian Medical Association Journal.

The drug works by reducing both the cravings and the pleasurable effects of cigarettes. t is one of the biggest-selling stop-smoking drugs in the United States.

People should be concerned. They do not need Chantix to quit and this is another reason to consider avoiding Chantix altogether, he said in a statement. People want to quit smoking to reduce the risk of cardiovascular disease, but in this case they are taking a drug that increases the risk for the very problems they are trying to avoid.

The findings, published July 4 in CMAJ are based on a review of more than 8,200 smokers or users of smokeless tobacco. About 4,900 took Chantix.

The researchers found that 52 (1.06 percent) of the participants taking Chantix had serious cardiovascular events compared with 27 (0.82 percent) of those taking the placebo.

Pfizer said it disagreed with Singh's interpretation of the data, calling the study lacking.

The analysis contains several limitations -- most notably that it is based on a small number of events, which raises concerns about the reliability of the authors' conclusions.

The authors acknowledge that their risk 'estimates are imprecise owing to the low event rates, the drug company explained.

The actual difference in cardiovascular event rates seen in the Singh analysis was less than one-quarter of one percent.

Overall the author of the study advised doctors to consider the potential cardiovascular and psychiatric problems before prescribing Chantix.

Pfizer banks around $800 million from the drug annually.