Varenicline reduces relapse rates in smokers who quit
Most smokers are powerfully addicted to nicotine. As a result, the success rate of unsupported quit attempts is very low, so there is plenty of room for treatments to improve results. Nicotine replacement is the best established therapy, but in 2000 the centrally acting oral treatment bupropion was launched in the UK. Now there is a new kid on the block called varenicline, and the Cochrane Tobacco Addiction Group have been casting their eye over the evidence for its effectiveness.
Varenicline is a nicotine receptor partial agonist, which basically means that it is specifically targeted to the receptors in the brain that are responsible for addiction. By competing with nicotine for these receptors it reduces the urge to smoke, while also reducing withdrawal symptoms because of its partial agonist effect. It is based upon a similar drug called cytisine, which has been used for many years as a stop-smoking aid in Central and Eastern Europe.
The Cochrane group reviewed five randomised controlled trials of varenicline versus placebo, and one relapse prevention trial. The six trials covered a total of 4,924 participants, 2,451 of whom were randomised to use varenicline. The main outcome measure was abstinence from smoking after at least six months from the start of treatment.
The pooled data showed that continuous abstinence at one year was increased threefold in those taking varenicline compared with placebo. It was also increased one and a half times compared with bupropion. The main adverse effect was nausea, which affected about a third of patients, although this was generally mild and self-limiting.
Although clinical experience with varenicline is limited, these are promising results.
These findings are supported by a recent NICE technology appraisal, which has recommended varenicline as an effective treatment to help smokers quit.1
Varenicline would appear to be more effective than bupropion, without the same potential for drug interactions. As such, it could become a powerful addition to the therapeutic armoury, particularly for smokers who are heavily dependent and have failed with nicotine replacement.
Cahill K, Stead LF, Lancaster T. Nicotine receptor partial agonists for smoking cessation. Cochrane Database of Systematic Reviews 2007, Issue 1. Art. No.: CD006103. doi: 10.1002/14651858.CD006103.pub2Reviewer
Dr Kevin Lewis
Former GP, Clinical Director of Smoking Cessation, Shropshire County Primary Care Trust