Belknap et al. investigated the impact of sulfonylurea on plasma lipids and glucose tolerance in 34 men from Seattle, Washington State, USA183. This was a double-blind crossover trial with random allocation of either 500 mg of tolbutamide twice daily or placebo taken for one year in random order. Subjects had a range of glucose intolerance from normal through to diabetic, though none were symptomatic. Baseline glucose levels suggest only three out of 34 subjects met current ADA criteria for diabetes. Nine men (21%) did not complete the two year trial (one year on each drug).
Very limited results were presented. No diabetes incidence was reported; however, it appeared that the active drug kept glucose levels from rising over baseline levels (+1 mg/dl, 0.056 mmol/L) whereas placebo levels increased more (+6 mg/dl, 0.33 mmol/L) leading to a significant difference at study end between active and control periods. The authors say that there were significant improvements in intravenous glucose tolerance, but present no results. No weight change occurred, and no improvements in triglycerides or total cholesterol were found. The small effects of tolbutamide seen in this crossover study with incomplete data presentation make it of limited use.
Another early trial of tolbutamide was conducted by Englehardt and Vecchio among oil company employees in Texas undergoing diabetes screen-ing184. Forty-two people with abnormal glucose tolerance by Fajans and Conn criteria were enrolled in a randomized, blinded study of 500 mg of tolbutamide
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