Mirtazapine‐Associated Rapid Weight Gain and Decreased Physical Activity

Background: Mirtazapine‐associated weight gain is widely documented. However, data demonstrating changes in physical activity associated with mirtazapine have not been published. Aim: To describe a case of rapid weight gain and decreased physical activity associated with mirtazapine. Clinical features: A 55‐year‐old Caucasian man was admitted after attempting suicide and was diagnosed with post‐traumatic stress disorder and depression. He was treated with mirtazapine 30 mg daily and zopiclone 15 mg at night during 5 weeks of hospitalisation and discharged on the same therapy. As a part of a research protocol, the patient was followed closely for 17 weeks after first observation, and his body weight, physical activity and biochemical parameters were recorded. Outcomes: The patient's weight increased by 10 kg within 2 weeks of starting mirtazapine, and at the end of the 17‐week follow‐up period the total weight gain was 17.5 kg. The fasting blood glucose and serum lipid concentrations had also increased. At the conclusion of the follow‐up period, physical activity levels had decreased by 40% relative to baseline. An objective causality assessment revealed that the relationship between mirtazapine and weight gain could be regarded as possible. Conclusion: Patients on mirtazapine should be monitored for changes in weight and offered information about diet and exercise to assist in weight management. J Pharm Pract Res 2004; 34: 308–9.