An international study found that Pzifer's anti-smoking drug Chantix, sold in Australia as Champix, is linked to a 72 percent greater risk of hospitalization due to a cardiovascular event like heart attack of arrhythmia. Pfizer immediately refuted the study which was released this Monday and defended to the drug's benefits to smokers.

The study published in the Canadian Medical Association Journal claims that the drug varenicline increases the chances of heart attack and stroke for people using the anti-smoking drug.

According to study's lead investigator Curt Furberg of Wake Forest Baptist Medical Center the drug is one of the most harmful prescription drugs on the US market.

"It causes loss of consciousness, visual disturbances, suicides, violence, depression and worsening of diabetes," he said in an AFP report. "To this list we now can add serious cardiovascular events."

Pfizer questioned the study's methodology noting that the 72 percent figure should be put into the appropriate context. According to the pharmaceutical giant there is actually less than a quarter of one percent difference between patients using Chantix and those using the placebo.

Varenicline works by targeting nicotine receptors in the brain to help reduce withdrawal symptoms. The drug has been the subject of numerous complaints since it was introduced. The European Medicines Agency and national agencies has already issued a warning about the increased risks of depression, suicidal ideas or suicide attempts in people who use the drug. More than 1,200 complaints have been filed in US courts about the side effects of the Chantix.

In Australia the drug is only available through prescriptions and is subsidized under the Government's Pharmaceutical Benefits Scheme. The head of the Melbourne-based cardiovascular disease research body Baker IDI Heart and Diabetes Institute doesn't believe the drug should be banned.

According to Professor Gary Jennings the smoking itself is more of a risk than the possible side effects of the drug.

"In fact, if you look at it literally and statistically, a person taking varenicline is more likely to give up smoking but has a 98.04 per cent chance of not having a cardiac event compared to a 99.18 per cent chance of not having an event on placebo," he said.

"Varenicline is authorized for short periods of use only, so limited exposure also minimizes the risk of harmful side effects.

"At this time, the study does not provide any basis for withdrawal of the drug here in Australia."