Findings by researchers at the University of Bristol from the largest review of clinical trials to date to determine whether patients prescribed the smoking cessation drug Varenicline (brand name Champix in the UK) are at an increased risk of neuro-psychiatric events have been published.
The drug, which was first licensed in the UK in 2006, has been shown to be the most clinically effective smoking cessation medicine for reducing nicotine cravings and withdrawal symptoms for short-term abstinence. However, since its introduction there have been concerns over its neuro-psychiatric safety following reports of adverse reactions to spontaneous reporting systems. These were reiterated in October 2014 when the US Food and Drug Administration (FDA) decided to keep the black box warning for Varenicline, the agency's strongest safety warning.
A team of researchers at the University of Bristol, carried out the first comprehensive published systematic review and meta-analysis to date on the neuropsychiatric effects associated with Varenicline use. Using results from 39 Varenicline studies the team identified a cohort of 10,761 participants that compared the effects of 5,817 patients who had received the maximum dose of 1mg of the drug twice daily and 4,944 patients who had received a placebo.
The findings showed no evidence of an increased risk of suicidal behaviour, depression or death in Varenicline users compared with those in placebo groups. Nor did the results show evidence for a variation in depression and suicidal behaviour by age group, sex, ethnicity, smoking status, or presence or absence of psychiatric illness.
The drug was found to be associated with an increased risk of sleep disorders including insomnia and abnormal dreams although these side effects are already well recognised and included in patient information leaflets. In addition, the results showed a 25% reduction in the risk of anxiety although this is likely to be explained by the positive impact of giving up smoking on mental health. Previous research has shown that smokers who quit have a reduction in depression and anxiety compared with those who continue to smoke.
Dr Kyla Thomas, a National Institute for Health Research clinical lecturer in public health based at Bristol’s School of Social and Community Medicine, who led the research, said: "This study represents the most comprehensive evaluation of adverse effects associated with Varenicline use to date and provides reassurance for both users and prescribers of this medicine. Ongoing fears regarding Varenicline's safety among prescribers and patients may be reflected in the 25% decrease in prescriptions observed between 2011 and 2013. Findings from this study show that the benefits of using Varenicline to give up smoking outweigh the yet unproven risks of suicidal behaviour. Therefore, the reduction in prescribing Varenicline should be as much a cause for concern to clinicians, regulatory agencies and policy makers as the unfounded fears regarding the drug’s association with suicidal behaviour."
[link url="http://www.bristol.ac.uk/news/2015/march/champix-study.html"]Bristol University material[/link]
[link url="http://www.bmj.com/content/350/bmj.h1109"]British Medical Journal abstract[/link]