For better glycemic control in diabetic patients, some studies recommend using the combination of NPH or insulin lispro with sulfonylurea. What is the rationale behind such combinations, given that the sulfonylureas are insulin secretagogues? Why not increase the insulin dosage or add metformin, rosiglitazone (Avandia), or pioglitazone (Actos) instead?
—Fadi I. Jabr, MD, Florence, Ore.
Data from both the United Kingdom Prospective Diabetes Study (UKPDS) (Diabetes Care. 2002;25:330-336) and a meta-analysis of randomized placebo-controlled trials (Arch Intern Med. 1996;156:259-264) show a modest but reliable improvement in glycemic control when combination insulin-sulfonylurea use is compared with insulin monotherapy. Presumably, this is due to increased endogenous insulin secretion resulting from the sulfonylurea and possibly some very limited extrapancreatic effect, such as a reduction in hepatic glucose production. That said, your suggestions represent viable alternatives.
— Daniel G. Tobin, MD (115-6)