A second study comparing varenicline to nicotine replacement therapy (NRT) has been published in Thorax.
This study was an observational, open label study involving approximately 750 patients so it is larger that the study already reported. The study measured self-reported continuous abstinence rate (CAR) confirmed by a carbon monoxide breath test for the last 4 weeks of treatment. Secondary outcomes included 52 week CAR.
The results of the study are as follows:
- CAR over last 4 weeks was statistically greater with varenicline (55.9%) than with NRT (43.2%) Relative Risk 1.70, [95% CI 1.26 to 2.28, p<0.001] NNT = 9
- CAR at week 52 was greater but not significantly different with varenicline (26.1%) than with NRT (20.3%) Relative Risk 1.40, [95% CI 0.99 to 1.99, p=0.056] NNT = 17 (May not be valid as difference was not statistically different)
- The most frequently reported side effect was nausea (37.2% with varenicline and 9.7% with NRT) NNH = 4
The authors of the paper openly discuss the limitations of the study citing the higher drop out rate and the higher numbers of treatment refusal in the NRT arm. The open label approach in this study may have created a differential in patient motivation that could have biased the results.
The results of this study demonstrate a higher initial efficacy with varenicline however this difference appears to reduce over time. The calculated Numbers Needed to Treat (NNT) shown above show that at the end of a primary course of treatment with varenicline there will be one more quitter but two people with nausea when compared to treatment with NRT.