OBJECTIVE To examine changes in glycemia and insulin secretion in response to SU per se and in response to a standard diet plus OD or TD SU therapy during chronic GP and GB therapy.

RESEARCH DESIGN AND METHODS Randomized (between agents and in order of dosing regimens), prospective, open, crossover study among 14 NIDDM patients to compare glucose, insulin, and C-peptide responses to a standard diet and to 10 mg of oral GP or GB taken without food 1) after 2 wk without therapy, 2) after 4 wk of either GP (n = 7) or GB (n = 7) treatment OD, and 3) after 4 wk of TD therapy with the same agent. Each patient received the same drug for maintenance therapy and for assessment of the response to the drug alone.

RESULTS We observed a comparable reduction in overall glycemia with both agents, with more marked postprandial effects for GP. Similar glucose, insulin, and C-peptide profiles for both agents during OD and TD therapy. Augmented insulin secretion in response to meals contrasting with reduced insulinotropic effects of the drugs per se with chronic therapy.

CONCLUSIONS Therapeutic equivalence of OD and TD dosing with GP and GB during chronic therapy. In view of the improved insulin secretion in response to nutrient stimuli, the attenuation of responses to SU per se during chronic therapy does not imply impairment of β-cell secretory capacity or represent a therapeutic disadvantage.