OBJECTIVES: We conducted a systematic review to assess the effect of pharmacist interventions on patients' medication adherence.

METHODS: Studies from five databases (Web of Science, PubMed, Cochrane Library, ScienceDirect, and Embase) since establishment to March 2024 were identified. The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) were used as guidelines for the review. Randomized controlled trials or observational studies comparing pharmacist intervention plus usual care to usual care among patient with chronic disease were included. Proportions of days covered (PDC) or percentage of adherent patients (defined as PDC≥80%) were used as the outcomes measured. The revised Cochrane Risk of Bias Tool and the Newcastle-Ottawa Scale were used to assess the quality of the studies. Weighted mean difference (MD) and the risk ratio (RR) were estimated in the meta-analysis for PDC and percentage of adherent patients, respectively. Heterogeneity was assessed using the I² statistic and random-effects model was used where I² exceeded 40%. Subgroup and sensitivity analysis were also conducted.

RESULTS: Among the 589 identified records, 15 of them were included for analysis. The meta-analysis found that the pharmacist intervention group generated higher PDC with MD of 0.08 (95% CI: 0.03-0.12, p=0.001, I²=100%) and higher percentage of adherent patients with RR of 1.09 (95% CI: 1.06–1.13, p <0.001, I² = 87%) compared with the usual-care group. Based on the results from different evaluation periods, pharmacist intervention improved adherence at both 6-month (RR=1.41 (0.68–2.92), p=0.36 , I²=64%) and 12-month (RR=1.15 (1.02–1.30), p=0.02 , I²=87%) assessment with higher improvement at the 6-month. By excluding the observational studies, similar results were estimated in the sensitivity analysis (MD=0.04 (0.01-0.07), RR=1.12 (1.04-1.21)).

CONCLUSIONS: Based on the results from the systematic review, pharmacist interventions can improve the medication adherence of patients compared with usual-care.