Regulators in the UK have joined the list of bodies to ask doctors to monitor the safety of Pfizer’s smoking cessation pill Champix.

The Medicines and Healthcare products Regulatory Agency has issued a drug safety update noting that as of September 29 it had received 3,541 adverse event reports, most of which are psychiatric disorders in patients taking Champix (varenicline). This figure is up from 1811 reports in February.

In addition, the MHRA reported that 10 people committed suicide after taking the drug, out of 24 deaths reported. Also 213 people claimed they experienced suicidal thoughts, while 407 complained of depression.

However the agency noted that the "suspected reactions are not necessarily caused by the drug” and may relate to other factors such as nicotine withdrawal, other illnesses or other medications taken concurrently by the patient”. Still, the MHRA said that “as Christmas and the time for New Year’s resolutions approach”, it was reminding healthcare professionals to highlight to those taking varenicline the possibility of adverse psychiatric effects.

The MHRA’s warning comes a year after the European Medicines Agency told Pfizer to update the label to include that cases of suicidal ideation and suicide attempts have been reported in patients who took the product. The warnings were updated in July.

In June the firm launched a staunch defence of Champix, after the USA-based nonprofit Institute for Safe Medication Practices organisation and analysed the side effects associated with the product that have been reported to the 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 results led the US Federal Aviation Administration to ban use of Chantix by pilots and air traffic controllers.