Orthostatic Hypotension from Therapeutic-dose Mirtazapine: A Case Report and Clinical Alert

A BSTRACT Orthostatic hypotension (OH) refers to a clinically significant decline in blood pressure upon standing. Mirtazapine, a tetracyclic antidepressant, has been typically associated with sedation and weight gain; however, cases of OH were rarely reported, predominantly in elderly patients at higher doses. This case reported a unique presentation of OH at a therapeutic dose (15 mg/day) in a young patient (body mass index: 22.4 kg/m²) without conventional risk factors – a combination not previously documented in the literature. A 40-year-old female with major depressive disorder presented with generalized weakness, dizziness, and lightheadedness after initiating mirtazapine. Clinical evaluation revealed significant hypotension (supine 122/78 mmHg to standing 88/52 mm Hg and heart rate: 72–96 bpm) without other identifiable causes. The Naranjo Adverse Drug Reaction Probability Scale yielded a score of 7, indicating a probable adverse drug reaction. Complete discontinuation of mirtazapine resulted in resolution of symptoms within 72 h, with blood pressure returning to baseline values. These findings underscored the need for clinicians to remain vigilant about potential OH even at standard doses of mirtazapine in patients without typical risk factors.