Re-Evaluation of Phenformin Therapy in Maturity-Onset Diabetic Patients

Nineteen adult, maturity-onset diabetic patients on combination sulfonylurea and phenformin treatment were studied at biweekly intervals for 1 year. Both drugs were continued for four months, after which phenformin was stopped for four months. In the third period of the study half the patients were restarted on phenformin and half received placebo for a two month period. In the fourth phase, also lasting two months, the phenformin and placebo group were switched. Mean plasma glucose concentrations (± SEM) in each period were: [Table Presented] Plasma lactate and pyruvate levels were lower oft phenformin than on therapy but lactate: pyruvate ratios were unchanged. No significant effects on basal glucagon and insulin concentrations were noted. Four patients had significant elevations of plasma triglycerides when phenformin was stopped but other chemistries were not affected. It is concluded that phenformin lowers the plasma glucose in most symptomatic maturity-onset diabetic patients even after continuous therapy for up to 16 years.