New research published today on bmj.com suggests there is no strong evidence that the popular smoking cessation drug varenicline increases the risk of self harm or depression compared to other cessation products.

The newly introduced Varenicline is a smoking cessation product of proven effectiveness. However, there have been concerns that it may increase the risk of suicidal behavior and suicide. Varenicline continues to be used widely, despite warnings about the probable increased risks issued by regulatory authorities worldwide.

A team of researchers from the University of Bristol and the UK’s Medicines and Healthcare products Regulatory Agency (MHRA) set out to provide further verification. They compared the risk of self harm among people taking varenicline with the risk of self harm associated with other smoking cessation products, such as bupropion and nicotine replacement therapy (patch, inhaler, gum, tablet or lozenge).

The researchers used data from the General Practice Research Database, including 80,660 men and women aged between 18 and 95 years. They were all prescribed a new course of smoking cessation product between September 2006 and May 2008.

Participants were prescribed nicotine replacement products (63,265), varenicline (10,973), or bupropion (6,422).

There was a review of all electronic patient records over the period of the prescription and for three months after the date of the last prescription. Incidences of fatal and non-fatal self-harm, suicidal thoughts and depression were examined.

Findings indicated there was no clear evidence of an increased risk of self harm, suicidal thoughts or depression associated with either varenicline or bupropion. Confounding factors were taken into account.

Although they found no strong evidence of an increased risk of self harm related to varenicline, the authors caution “the limited power of the study means we cannot rule out either a halving or a twofold increased risk.”

They recommend further investigation of varenicline’s effect on suicide risk in other databases and secondary analysis of all adverse events reporting in clinical trials.

In closing, they caution that any risks must be weighed against the long term health benefits of stopping smoking and the effectiveness of varenicline as a smoking cessation product.

“Varenicline and suicidal behaviour: a cohort study based on data from the General Practice Research Database”
D Gunnell, professor of epidemiology, D Irvine, pharmacoepidemiologist, L Wise, senior pharmacoepidemiologist, C Davies, senior pharmacovigilance assessor, R M Martin, professor of clinical epidemiology
BMJ 2009; 339:b3805
doi:10.1136/bmj.b3805
bmj.com

Written by Stephanie Brunner (B.A.)