METFORMIN TREATMENT IN NIDDM PATIENTS WITH MILD RENAL IMPAIRMENT

Metformin is contraindicated in patients with renal failure because of the risk of lactic acidosis. This study assessed the complications of metformin treatment in patients with non-insulin-dependent diabetes m ellitis with normal and raised serum creatinine. Subjects using metfor min with serum creatinine above the upper reference range (120 mu mol/ l) were identified (n=17) fi om a hospital diabetes register; those wi th abnormal liver function, cardiac failure, peripheral vascular disea se or recent severe illness were excluded. Reference plasma lactate le vels were established, mean 1.742 mu mol/l (SD 0.819) using age-matche d non-diabetic subjects. Age-matched patients treated with metformin w ith normal serum creatinine levels formed the control group (n=24). De tails of gastrointestinal disturbance were recorded, and plasma lactic acid and vitamin B12 levels measured. The median total daily dose of metformin in both groups was 1700 mg. The mean plasma lactate in subje cts with serum creatinine 80-120 mu mol/l (2.640 mmol/l (SD 1.434) p < 0.02) was higher than non-diabetic control levels while diabetic subj ects with serum creatinine 120-160 mu mol/l had a mean of 2.272 mmol/l (SD 0.763) p < 0.05. There was no significant difference between the two groups taking metformin, nor any significant difference in the rep orting of gastrointestinal symptoms between the groups on metformin (1 1.76% vs 12.5%). Plasma lactic acid levels are higher in diabetic subj ects taking metformin compared with healthy volunteers but, within the diabetic groups, the small elevation of serum creatinine was not asso ciated with higher plasma lactate levels.