Background: Adverse drug events and medication errors are threats to quality care. Inpatient studies suggest that a pharmacist may reduce these events, but outpatient studies have not been forthcoming.
Methods: We conducted a pooled analysis of 2 randomized controlled trials to determine the effect of pharmacist intervention on adverse drug events and medication errors. We studied 800 outpatient cases of hypertension stratified into complicated (n = 535) and uncomplicated (n = 265). Patients in the complicated stratum had heart failure or other cardiovascular complication. Computer programs examined 1-year electronic record data to identify events classified as adverse drug events and preventable or potential adverse drug events. Medication errors included preventable and potential adverse drug events.
Results: Of the 800 participants (mean [SD] age, 59  years), 484 (90.5%) and 258 (97.4%) participants remained in the complicated and uncomplicated strata, respectively, at 12 months. Compared with the control group, the risk of any event was 34% lower in the intervention group (risk ratio, 0.66; 95% confidence interval [CI], 0.50-0.88), including a lower risk of adverse drug events (risk ratio, 0.65; 95% CI, 0.47-0.90), preventable adverse drug events (risk ratio, 0.52; 95% CI, 0.25-1.09), potential adverse drug events (risk ratio, 0.70; 95% CI, 0.40-1.22), and medication errors (risk ratio, 0.63; 95% CI, 0.40-0.98).
Conclusions: This post hoc analysis suggests that pharmacist intervention to improve medication use in outpatients with cardiovascular disease decreases the risk of adverse drug events and medication errors. Further studies are needed to confirm this finding.