Hypersensitivity. Diabetic ketoacidosis & pre-coma; renal failure/dysfunction (CrCl <60 mL/min); acute conditions w/ potential to alter renal function eg, dehydration, severe infection, shock; acute or chronic disease which may cause tissue hypoxia eg, cardiac or resp failure, recent MI, shock; hepatic insufficiency, acute alcohol intoxication, alcoholism. Childn.