Zopiclone-Induced Methemoglobinemia: A Case Report Highlighting How the Treatment Differs in Patients on Serotonergic Medication

TL;DR

A patient overdosed on zopiclone and developed a rare blood condition, which was treated with ascorbic acid due to risks from antidepressant use.

Contribution

Highlights the alternative treatment of ascorbic acid for zopiclone-induced methemoglobinemia in patients on serotonergic medication.

Findings

Zopiclone overdose can cause methemoglobinemia, indicated by a saturation gap and chocolate-brown arterial blood.

Ascorbic acid was safely used instead of methylene blue to avoid serotonin syndrome in a patient on antidepressants.

Early recognition of methemoglobinemia is critical for effective and life-saving treatment.

Abstract

Zopiclone is a sedative-hypnotic that is increasingly being used for insomnia, especially among patients with depression. The side effects of zopiclone include nausea, vomiting, headache, giddiness, sedation, altered mental status, and coma. Here, we describe a rare case of a patient with underlying depression who overdosed on zopiclone, resulting in a presentation of drowsiness and dyspnea. A diagnosis of methemoglobinemia was made only through astute observation of the presence of a saturation gap, poor oxygen saturation despite high flow oxygen supplementation, and the arterial blood gas sample appearing chocolate brown in color. Treatment of such patients usually includes the gold standard of methylene blue. However, in our case, there was a risk of serotonin syndrome as the patient was on a serotonergic antidepressant prior. As such, an alternative treatment with ascorbic acid was utilized instead. Methemoglobinemia, while uncommon, should always be suspected in patients who present with zopiclone overdose as it can be life-threatening and is easily treatable.