Pfizer has received a jolt on the publication of a study which claims that the firm’s smoking cessation product Chantix has been linked to more than 3,000 reports of adverse events including “attempted and completed suicide”.

The nonprofit Institute for Safe Medication Practices organisation has issued a report which analyses the side effects associated with Chantix (varenicline) that have been reported to the US Food and Drug Administration. The ISMP noted that these included 227 reports of suicidal acts, thoughts or behaviours, 397 cases of possible psychosis and 525 reports of hostility or aggression. These figures included 28 cases of suicide and 41 mentions of homicidal ideation, 60 cases of paranoia and 55 cases of hallucination.

The ISMP added that “we have immediate safety concerns about the use of varenicline” among people operating aircraft, trains, buses and other vehicles, due to reports of “sudden loss of consciousness, seizures, muscle spasms, vision disturbances, hallucinations, paranoia and psychosis”. As such, “we believe varenicline may not be safe to use in these settings”, the group said.

The effect of the report was immediate and the USA’s Federal Aviation Administration has now banned the use of Chantix by pilots. It comes three months after the FDA said that the drug could be linked to serious psychiatric problems, just a fortnight after the firm updated its label on the product.

Prescriptions for Chantix have fallen appreciably of late amid these fears and Tim Anderson, an analyst at Sanford Bernstein, has cut sales estimates for the drug by 42% to $758 million for 2009. He issued a research note saying that “the launch of Chantix had been a bright spot for Pfizer until safety issues surfaced in November 2007 that have since sent performance into a tailspin''.

Pfizer responded by saying that "the current Chantix label accurately reflects the product's efficacy and safety profile."