Lactic acidosis after concomitant treatment with metformin and tenofovir in a patient with HIV infection.

We present an uncommon case of lactic acidosis after concomitant administration of Metformin and Tenofovir. This is a 74-year-old man with a history of diabetes mellitus receiving treatment with metformin. He had coronary artery disease and HIV infection treated with emtricitabine, tenofovir and recently started on efavirenz. He presented with zoster-like abdominal pain, tachypnoea, nausea and vomiting. On clinical examination, the patient was afebrile, hypotensive and tachycardic, he was markedly dehydrated and oliguric. The abdomen was soft, tender on palpation, not distended without rebound tenderness. The arterial blood gases revealed marked lactic acidosis and the laboratory tests on admission showed acute renal failure. The patient received nine treatments of slow continuous veno-venous hemofiltration (CVVHF). Despite the prolonged period of anuria, urine output progressively improved after 25 days and serum biochemical parameters of renal function returned to normal within 40 days. Health professionals must be aware of this uncommon effect in patients on antiretroviral treatment. Prompt initiation of CVVHF resulted in resolution of both lactic acidosis and renal failure.