Sulphonylurea and insulin: combined treatment in Type 1 (insulin-dependent) diabetes
Dear Sir, In contrast to the recent observations of Ratzmann et al. [1] that tolbutamide is not a useful adjunct to insulin treatment in Type 1 diabetes, I would like to refer to our recent work on a similar theme [2]. We demonstrated that when a combination of insulin and glibenclamide treatment was given to patients with Type i diabetes in a randomized and double-blind cross-over trial for periods of 3 months, measurements of diabetic control improved significantly in those patients who retained residual endogenous insulin secretion. During an oral glucose tolerance test 3 months after combined treatment, C-peptide secretion increased by 47%, the mean + SD daily blood glucose level fell from 8.4+ 1.7 to 7.4+ 1.5 mmol/1 (p < 0.02) and the mean glycosylated haemoglobin decreased from 8.1_+0.5% to 7.5_+0.9% (p <0.05). These results substantiate a previous study [3] which showed that glibenclamide, when added to the insulin regimen of Type 1 diabetic patients with residual insulin secretion, increased their C-peptide secretion by 60% over a 1-month period. Less than half of the seven subjects in Ratzmann et al.'s study could be described as having retained residual endogenous insulin secretion according to the criteria of Madsbad [4] of a plasma C-peptide concentration > 0.07 mmol/1. Although limited insulin and glibenclamide treatment may be only of limited value, I believe that further research is needed to follow up our observations and determine how long increased insulin secretion and improved metabolic control persist. Yours sincerely,