Varenicline: quantifying the risk

We agree that there is a lack of clarity in Singh and colleagues’ article; it is very difficult for readers to follow how the various assumptions and extrapolations have been made.1

The rather alarming figure of a 72% increase in serious cardiovascular events has been picked up by the media. However, in absolute terms, the increase in risk is only 0.24%, which computes to an NNH (number needed to harm) of about 400. This is a very small increase in risk compared with the benefits of quitting smoking (number needed to treat 10 for varenicline).

Admittedly, Singh and colleagues’ study may signal the need for caution when using varenicline in patients with a history of cardiovascular or active disease. The authors need to offer more explanation about how they reached the estimate of NNH of 28, which appears to be an extrapolation of their findings to a population at very high risk of cardiovascular disease.