Varenicline is a recently introduced smoking cessation product of proven effectiveness, but there have been concerns that it may increase the risk of suicidal behaviour and suicide. Despite warnings about the possible increased risks issued by regulatory authorities worldwide, varenicline continues to be used widely.
To provide more evidence, Professor David Gunnell and colleagues from the University of Bristol and the Medicines and Healthcare products Regulatory Agency (MHRA) compared the risk of self harm among people taking varenicline with the risk of self harm associated with other smoking cessation products, bupropion and nicotine replacement therapy (patch, inhaler, gum, tablet or lozenge).
Using data from the General Practice Research Database, 80,660 men and women aged between 18 and 95 years were identified who were prescribed a new course of smoking cessation product between September 2006 and May 2008.
Nicotine replacement products were prescribed to 10,973 participants, varenicline to 10,973 and bupropion to 6,422.
All electronic patient records over the period of the prescription and for three months after the date of the last prescription were examined for incidences of fatal and non-fatal self-harm, suicidal thoughts and depression.
In total, there were 166 incidences of self-harm and two suicides (both in patients prescribed nicotine replacement therapy).
After controlling for confounding factors, there was no clear evidence of an increased risk of self harm, suicidal thoughts or depression associated with either varenicline or bupropion.
The authors caution that although they found no strong evidence of an increased risk of self harm linked to varenicline, “the limited power of the study means we cannot rule out either a halving or a twofold increased risk.”
They go on to call for more investigation of varenicline’s effect on suicide risk in other databases and secondary analysis of all adverse event reporting in clinical trials.
They conclude by cautioning that any risks must be balanced 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 by D Gunnell, D Irvine, L Wise, C Davies and R M Martin bmj.com