Numerous studies have led to warnings being issued by regulatory agencies about varenicline, a widely prescribed smoking cessation drug. However, a new study suggests that there is no strong evidence to link the drug with increased risks of suicidal behavior or traffic accidents as previously thought.
The study, published in The BMJ, examined 69,757 individuals in Sweden aged 15 and above who were prescribed the drug between 2006 and 2009.
Between 2006 – when varenicline was approved by the US Food and Drug Administration (FDA) – and mid-2011, a total of 8.9 million people in the US were treated with the drug. Varenicline works by relieving withdrawal symptoms while simultaneously decreasing the rewards of smoking.
Although multiple studies have indicated that the drug is more effective in aiding smoking cessation than placebo, bupropion or single forms of nicotine replacement therapy, evidence has been presented linking varenicline with suicidality, depression and an increase in traffic accidents.
Due to these reports, use of the drug has been restricted or prohibited in some professions such as pilots, air traffic controllers and certain military personnel. Additionally, the drug is subject to a black box warning in the US.
In March, the FDA updated the label for varenicline, warning that use of the drug could alter the way the body reacts to alcohol and on rare occasions lead to seizures. In 2011, another study suggested that the drug had too poor a safety profile to make it suitable for first-line use.
“However, these increased risks are based on post-marketing surveillance and case reports, which are not consistent with observational data and randomized controlled trials that have found no association between varenicline and depression, suicidality, or violence,” write the authors.
Researchers from the Karolinska Institutet in Sweden and the University of Oxford in the UK set out to address these inconsistencies with a population-based cohort study using data obtained from national registers to measure a range of adverse outcomes such as suicidal behavior, criminal offending, transport accidents and traffic offenses.
“In between person analyses, adjusted for age and sex, we found that people taking varenicline had increased hazards of the adverse events investigated,” write the authors.
“However, when we compared periods of treatment with periods of non-treatment within the same person to control for confounding by indication, our principal analytical approach, we found no associations with suicidal behavior, suspected and convicted criminal offending, transport accidents, or suspected and convicted traffic offenses.”
The researchers did observe among individuals with pre-existing psychiatric disorders a small increased risk of mood and anxiety conditions in association with periods of medication. They state that this increase “requires confirmation using other study designs.”
As the study was an observational one, the authors are unable to draw any definitive conclusions from their findings. Additionally, the study is limited by a lack of information on time-varying variables and a reliance on events that resulted in hospital admissions or police reporting.
Despite these limitations, the authors state their findings “provide no evidence for a causal association between varenicline and criminal offending, transport accidents, traffic offenses, or psychoses.”
The study was funded by the Wellcome Trust, the Karolinska Institutet, the Swedish Research Council and the Swedish Research Council for Health, Working Life and Welfare.
Recently, Medical News Today reported on a study investigating whether cash incentives would help employees to quit smoking. Although popular, the incentive was not as effective at leading to cessation as a program offering potential winnings only after an up-front deposit was given.