Effect of the withdrawal of phenformin on glycaemic control and on lactate production during exercise in non-insulin dependent diabetics

Summary To evaluate the metabolic effects of phenformin in non-insulin-dependent diabetics, 9 patients who had been treated for a long time with associations of sulphonyl-ureas and phenformin were submitted to exercise on a cycloergometer before and 7 days after the withdrawal of phenformin. Greater lactate production and lactate/pyruvate ratio during exercise without phenformin were observed in 8 of the 9 subjects, concomitant with worsened glycaemic control. The reverse was observed in 1 subject. In the 8 subjects, lactate and the lactate/pyruvate ratio approximated to the values observed in 8 well-controlled diabetics during phenformin treatment and to those observed in 9 poorly-controlled subjects after the withdrawal of phenformin. It is suggested that phenformin facilitates glucose utilization in non-insulin-dependent diabetics provided that it lowers their glycaemic profiles.