Seven RCTs and two controlled trials met the inclusion criteria. Eight trials (n=11,597) were included in the meta-analyses. One RCT, which met the inclusion criteria, was excluded from all the statistical pooling because of the small sample size and the fact that the intervention was not OTC, owing to the amount of contact with participants. A further RCT was excluded from the meta-analysis of actual abstinence rates as the 10-week follow-up was considered too short.

OTC NRT versus OTC placebo (4 RCTs, n=2,290).

OTC NRT was significantly more effective than placebo (OR 2.5, 95% CI 1.8, 3.6). There was no evidence of statistical heterogeneity (P=0.8).

OTC NRT versus prescription NRT (2 RCTs and 2 controlled trials, n=9,307).

At the 6-month follow-up, OTC NRT and prescription NRT produced equivalent rates of abstinence (OR 1.4, 95% CI: 0.6, 3.3). There was evidence of statistical heterogeneity (P=0.01).

Actual abstinence rates with OTC NRT (5 RCTs and 2 controlled trials).

The mean 6-month abstinence rate was 7% (95% CI: 4, 11). There was evidence of statistical heterogeneity (P=0.01).