Metformin efficacy and tolerance in obese non-insulin dependent diabetics: a comparison of two dosage schedules.

A comparative open study of metformin unit doses of 500 mg and 850 mg was carried out in 64 obese, non-insulin dependent diabetics on 1.5 to 3 g metformin daily. Glycaemic response, blood lactate, plasma metformin concentrations and tolerance for metformin were assessed. On changing from a 500 mg unit dose to an equivalent total dose of metformin using the 850 mg preparation, there were no significant changes in the random blood glucose, glycated haemoglobin, or blood lactate concentrations. Metformin plasma concentrations remained unchanged except for patients transferred from 1.5 to 2.0 g daily to 850 mg twice daily; in these patients plasma concentrations increased from 1.83 +/- 0.87 to 2.50 +/- 0.89 micrograms/l (p less than 0.01). Seven patients (3 asymptomatic and 4 with background symptoms) became intolerant of the 850 mg regimen and required to return to the 500 mg dose regimen. After exclusion of patients intolerant of the 850 mg dose regimen (11%), the remaining patients noted no significant change in symptoms and 28% of all patients transferred to the 850 mg dose unit indicated an overall preference for this regimen.