Real-World Anthropometric Outcomes, Safety, and Use Patterns of GLP-1 and Dual GIP/GLP-1 Receptor Agonists in Obesity and Glucose Metabolism Disorder: A Nationwide Multicentre Community Pharmacy Study

Background: Glucagon-like peptide-1 receptor agonists (GLP-1RAs) have transformed the management of obesity and type 2 diabetes mellitus (T2DM). Although randomized clinical trials have demonstrated substantial weight loss and metabolic benefits with incretin-based therapies, real-world evidence is needed to characterize anthropometric outcomes, safety, prescribing patterns, and treatment use under routine clinical conditions. Objectives: The objective of this study was to characterize real-world anthropometric outcomes, safety, and use patterns of GLP-1 receptor agonists and dual GIP/GLP-1 receptor agonists in patients with obesity or glucose metabolism disorder receiving treatment through Spanish community pharmacies. Methods: A nationwide multicentre cross-sectional study with retrospective data collection was conducted between January and April 2026 across community pharmacies in Spain. Adult patients receiving GLP-1 receptor agonists or dual GIP/GLP-1 receptor agonists were consecutively enrolled and classified according to therapeutic indication (obesity or glucose metabolism disorder). Changes in body weight and body mass index (BMI) were assessed using paired-sample t-tests, while multivariable linear regression explored independent determinants of weight loss. Crude safety signals were initially evaluated using exploratory crude safety association analysis based on Odds Ratios (ORs). Subsequently, multivariable logistic regression was performed to identify independent predictors of suspected digestive adverse drug reactions after adjustment for demographic characteristics, treatment-related variables, lifestyle factors, and concomitant glucose-lowering therapies. Baseline body weight was retrospectively reported by participants and was not independently verified against clinical records or other objective sources, whereas current body weight was measured by the pharmacist at the study visit. Results: A total of 531 patients were included (52.2% with obesity; 47.8% were classified in the glucose metabolism disorder (GMD) cohort, comprising 200 patients with type 2 diabetes mellitus and 54 with prediabetes/fasting glucose disturbance; the mean age was 56.5 ± 12.5 years; and 66.7% were women). The mean observed reduction in body weight from treatment initiation to the study assessment was 12.17 ± 10.64 kg, corresponding to an 11.71% ± 9.40% reduction relative to retrospectively reported baseline weight. Overall, 73.9% and 54.1% of participants achieved ≥5% and ≥10% weight loss, respectively. No statistically significant unadjusted difference in relative weight loss was detected across treatment groups; however, equivalence was not formally assessed. Gastrointestinal suspected adverse drug reactions were the most frequently reported safety outcomes. Exploratory crude analyses showed nominal associations between Wegovy® and nausea/vomiting and between Mounjaro® and constipation, as well as between concomitant insulin and dizziness and SGLT2 inhibitor therapy and urinary disorders; however, none of these associations remained statistically significant after Benjamini–Hochberg correction for multiple testing. In the exploratory multivariable linear regression model, treatment duration, treatment agent, dietary adherence, light physical activity, and age showed statistically significant adjusted associations with observed percentage weight loss. In the multivariable logistic regression model, increasing age was the only variable significantly associated with lower odds of reported suspected digestive adverse drug reactions (adjusted OR = 0.97 per year; 95% CI 0.96–0.99; p = 0.003). Conclusions: Observed percentage weight loss varied across treatment groups, although between-treatment comparisons should be interpreted cautiously because of differences in treatment duration, therapeutic indication, sample size, and dose exposure. Given the retrospective ascertainment of baseline weight and the cross-sectional design, these findings should be interpreted as real-world estimates of observed weight change rather than causal estimates of treatment effectiveness. Reported suspected adverse drug reactions were common, particularly gastrointestinal events. Although several nominal associations were observed in exploratory crude analyses, none remained statistically significant after correction for multiple testing. These findings support the importance of individualized monitoring in community pharmacy settings. These findings provide a rationale for the prospective development and evaluation of a standardized pharmacy-led dispensing and follow-up protocol to support patient safety and treatment adherence.