Mirtazapine for gastrointestinal side effects of glucagon-like peptide-1 receptor agonist therapy in older adults

<b>Objective.</b> Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) play a role in management of type 2 diabetes (T2D) and obesity by promoting glycemic control and weight reduction. Beyond these benefits, GLP-1 RAs have demonstrated positive effects on cardiovascular, renal, and neurological health, with emerging evidence supporting their therapeutic potential in conditions such as chronic kidney disease, asthma, obstructive sleep apnea, Parkinson's disease, and Alzheimer's disease. However, their widespread clinical use is often hindered by gastrointestinal side effects including nausea, anorexia, vomiting, and diarrhea that limit adherence and dose titration. Effective management of these adverse effects is essential to optimize treatment outcomes and maintain long-term therapy. <b>Case report.</b> A 72-year-old woman with a history of cognitive impairment, T2D, atrial fibrillation, obesity, and mood disorders presented with persistent gastrointestinal symptoms while receiving semaglutide. Dose escalation was restricted due to severe nausea, vomiting, and diarrhea, which markedly affected her quality of life. To manage these symptoms, mirtazapine was initiated. Following its introduction, the patient reported significant improvement in gastrointestinal tolerance enabling continued semaglutide therapy and successful dose advancement. Additional benefits included enhanced mood, better sleep, and overall well-being. No adverse effects related to mirtazapine were observed throughout the treatment. <b>Conclusion.</b> This case suggests that mirtazapine may be beneficial in mitigating GLP-1 RA-induced gastrointestinal side effects, thereby improving adherence and therapeutic efficacy. Further research is needed to evaluate the safety, mechanism, and generalizability of this approach in broader clinical practice.