A study on Monday showed anti-smoking drug Chantix poses significant cardiovascular risks. Pharmaceutical giant Pfizer denied the claim immediately, while defending the drug's benefits.
According to the study published in the Canadian Medical Association Journal, the drug varenicline (brand name Chantix) is linked to a 72 percent greater risk of hospitalization due to a serious adverse cardiovascular event like a heart attack or arrhythmia.
"We have known for many years that Chantix is one of the most harmful prescription drugs on the US market, based on the number of serious adverse effects reported to the FDA" (US Food and Drug Administration), said study lead investigator Curt Furberg of Wake Forest Baptist Medical Center.
"It causes loss of consciousness, visual disturbances, suicides, violence, depression and worsening of diabetes," he said in a statement. "To this list we now can add serious cardiovascular events."
Pfizer promptly responded to the accusations and critiqued the study's methodology, noting that "the difference of 72 percent reported in the Singh analysis also needs to be put into appropriate context."
The firm said the actual difference in cardiovascular complaints between patients using Chantix and those using a placebo reported in the study analysis was less than a quarter of one percent.
The FDA has asked Pfizer to conduct several clinical studies that cross-prescribe Chantix and placebo groups to different patient groups.
As of the beginning of the year, more than 1,200 complaints had been filed in US courts about the side effects of Chantix.
The drug is sold in nearly 90 countries and used by seven million Americans.
The European Medicines Agency and national agencies issued a warning as early as December 2007 over the risks of depression, suicidal ideas or suicide attempts in people who use the drug, known as Champix in France, to quit smoking.