Objective To evaluate the impact of comparative performance feedback to community pharmacists on provision of professional services and the quality of patients’ medication use.

Design Randomised, controlled, single-blind trial.

Setting All 1833 community pharmacies in the Quebec province, Canada.

Participants 1814 pharmacies not opting out and with more than 5 dispensings of the target medications during the 6-month baseline were randomised by a 2×2 factorial design to feedback first for hypertension adherence (907 control, 907 intervention) followed by randomisation for asthma adherence (791 control, 807 intervention). 1422 of 1814 pharmacies had complete information available during the follow-up for hypertension intervention (706 intervention, 716 control), and 1301 of 1598 had the follow-up information for asthma (657 intervention, 644 control).

Intervention Using provincial billing data to measure performance, mailed comparative feedback reported the pharmacy-level percentage of dispensings to patients non-adherent to antihypertensive medications or overusing asthma rescue inhalers.

Primary and secondary outcome measures The number of hypertension/asthma services billed per pharmacy and percentage of dispensings to non-adherent patients over the 12 months post intervention.

Results Feedback on the asthma measure led to increased provision of asthma services (control 0.2, intervention 0.4, RR 1.58, 95% CI 1.02 to 2.46). However, this did not translate into reductions in patients’ overuse of rescue inhalers (control 45.5%, intervention 44.6%, RR 0.99, 95% CI 0.98 to 1.01). For non-adherence to antihypertensive medications, feedback resulted in no difference in either provision of hypertension services (control 0.7, intervention 0.8, RR 1.25, 95% CI 0.86 to 1.82) or antihypertensive treatment adherence (control 27.9%, intervention 28.0%, RR 1.0, 95% CI 0.99 to 1.00). Baseline performance did not influence results, and there was no evidence of a cumulative effect with repeated feedback.

Conclusions Comparative pharmacy performance feedback increased the provision of asthma pharmacists’ services but did not improve the performance on medication-use measures. Billing data can be used to evaluate the impact of billable services rendered by pharmacists on the quality of patients’ medication use.