Case Study: Metformin-Associated Lactic Acidosis: Could orlistat be relevant?

Lactic acidosis is a rare (1) but serious complication of metformin therapy with a high fatality rate (2). In the majority of reported cases there is a preexisting disease, most often a degree of renal impairment. We present a case of metformin-associated lactic acidosis (MALA) where drug interactions (orlistat in the long term and cimetidine over a short period of time) may have potentiated the condition. A 59-year-old woman with type 2 diabetes for 14 years presented with a history of 3 months of vague abdominal pain and four to five loose bowel movements daily, which worsened over the 4 days before admission to hospital. On the day of admission she reported weakness, dizziness, and blurred vision. Her husband had noticed slurred speech and a reduced level of consciousness. There was a past history of a healed duodenal ulcer and obesity. She had documented normal renal function 4 months before this admission (urea 5.7 mmol/l and creatinine 105 μmol/l). Her diabetes was well controlled on metformin at 500 mg t.i.d. for the past 8 years. Three months before admission she started orlistat at 120 mg t.i.d., which coincided with the onset of the abdominal pain and chronic diarrhea. During the 4 …