An Unusual Association Between Metformin and Nightmares: A Case Report.

Metformin remains the oral drug of choice for patients with type 2 diabetes mellitus (T2DM). It is an ideal anti-diabetic drug for maintaining good glycemic control in diabetics. However, the side effect profile of metformin varies from minor or no effects to substantial impact on the GI tract. In addition, metformin is rarely known for its association with nightmares. Here we present the case of a newly diagnosed 40-year-old diabetic who developed recurrent nightmares within a week of starting metformin treatment. The patient had no previous history of psychiatric or sleep disorders. However, it was the first time he had experienced such recurrent nightmares, especially after the start of 500 mg metformin thrice a day. Based on the Naranjo Adverse Drug Reaction (ADR) Probability Scale, and sudden onset and disappearance of nightmares after metformin initiation and discontinuation made metformin the primary cause of his nightmares.