Relative safety of mirtazapine overdose

A 43-y-o male with a history of AIDS, atrial fibrillation, and alcohol abus e presented to the emergency department 2 h after ingestion of 25 tablets o f 15 mg mirtazapine (total 375 mg) with ethanol in a suicide attempt (no ot her coingestion). Vital signs were normal except for a mild tachycardia (ra te 112), Physical examination was unremarkable except for lethargy. Fifty g rams of activated charcoal with sorbitol was given. Electrocardiogram showe d sinus tachycardia, left ventricular hypertrophy, and non-specific ST-segm ent changes. Serum mirtazapine on admission was 530 ng/mL (therapeutic leve l 20-50 ng/mL). Overnight monitoring revealed no tachyarrythmias, and disch arge occurred after psychiatric evaluation. It appears that ingestions of m irtazapine approximately 10-fold of therapeutic exhibit minimal acute toxic ity. From this and other cases in the literature exhibiting a 10-fold overd ose, we conclude that isolated mirtazapine ingestions of this magnitude req uire no acute intervention other than short term (about 6 h) observation.