Clinical pharmacist-led interventions and their impact on outcomes in patients with bipolar I disorder: a systematic review and meta-analysis

Background Pharmacist-led interventions have increasingly been recognized as effective strategies for improving outcomes in psychiatric care, yet their role in patients with bipolar I disorder (BD-I) remains underexplored. This systematic review and meta-analysis synthesized existing evidence on the impact of clinical pharmacist-led interventions (defined as medication education, medication review, adherence support, relapse monitoring, and collaborative care with psychiatrists) on medication adherence, relapse prevention, hospitalization, and quality of life among individuals with BD-I. Objectives To evaluate the effectiveness of pharmacist-led interventions, either alone or in collaboration with psychiatrists, on key clinical and humanistic outcomes in adults diagnosed with BD-I. Methods Electronic databases (PubMed/MEDLINE, Embase, PsycINFO, Scopus, Web of Science, and the Cochrane Library) were searched from January 2000 to August 2025 for randomized controlled trials and non-randomized quasi-experimental designs (prospective cohort studies and pre–post intervention studies) assessing pharmacist-led interventions in BD-I. Studies were screened and appraised independently in accordance with PRISMA 2020 guidelines, using the Cochrane RoB 2 tool for randomized controlled trials and the Newcastle–Ottawa Scale for non-randomized studies. Meta-analyses were performed using Review Manager (RevMan 5.4). Primary outcomes were medication adherence, relapse, hospitalization, and health-related quality of life (QoL). Secondary outcomes included any additional clinical or humanistic measures reported by the included studies. Effect sizes were expressed as odds ratios (ORs) for dichotomous outcomes and as mean differences (MDs) or standardized mean differences (SMDs) for continuous outcomes, each reported with 95% confidence intervals (CIs). Results Five studies met the eligibility criteria, and four contributed quantitative data. Pharmacist-led interventions significantly improved medication adherence compared with usual care (MD = 1.47 [95% CI: 1.35–1.59], p < 0.00001). For relapse prevention, pooled analysis from two trials showed reduced relapse episodes (OR = 1.94 [95% CI: 1.15–3.23], p = 0.01; I 2 = 38%). Improvements were also observed in quality of life (SMD = –1.89 [95% CI: –4.95–1.20], p = 0.21; I 2 = 90%). Evidence for hospitalization reduction was limited but directionally favored pharmacist involvement. Conclusion Clinical pharmacist-led interventions significantly enhance medication adherence and quality of life and may reduce relapse risk among patients with BD-I. However, given the limited number of studies and small pooled sample sizes, the overall evidence remains preliminary, and the findings should be interpreted cautiously rather than as definitive conclusions. Further large-scale, multicenter studies are warranted to confirm these benefits and assess cost-effectiveness. Systematic review registration [ https://www.crd.york.ac.uk/prospero/ ], identifier [CRD420251123737 04/10/2025].