['To compare the effects of intravenously administered long-acting insulin analog glargine and regular human insulin on activation and deactivation of endogenous glucose output (EGO) and peripheral glucose uptake.', 'In this single-center, randomized, double-blind, crossover euglycemic glucose clamp study, 15 healthy male volunteers (aged 27 +/- 4 years, BMI 24.2 +/- 0.7 kg/m(2) [mean +/- SE]) received a primed continuous intravenous infusion of 40 mU/m(2) of insulin glargine or regular human insulin on 2 different study days in a randomized order. Euglycemia was maintained at 90 mg/dl using a simultaneous variable intravenous infusion of 20% dextrose containing D-[3-(3)H]glucose. EGO and peripheral glucose disposal kinetics were determined during a 4-h insulin infusion activation period and a 3-h deactivation period.', 'The results demonstrated no significant difference in activation or deactivation kinetics with respect to EGO and peripheral glucose disposal between insulin glargine and regular human insulin when given intravenously. The mean +/- SE time required for 50% suppression of EGO after insulin infusion was 73 +/- 23 min for regular insulin and 57 +/- 20 min for insulin glargine (NS). The mean maximum rate of glucose disposal was 10.10 +/- 0.77 and 9.90 +/- 0.85 mg. kg(-1). min(-1) for regular insulin and insulin glargine, respectively (NS). The mean time required for 50% suppression of incremental glucose disposal rate (GDR), defined as the time required for activation from the basal glucose disappearance rate (R(d)) to half-maximum insulin-stimulated R(d), was 32 +/- 5 and 42 +/- 10 min for regular insulin and insulin glargine, respectively (NS). The time required for deactivation from maximum insulin-stimulated GDR to half-maximum GDR after cessation of insulin infusion was 63 +/- 5 and 57 +/- 4 min for regular insulin and insulin glargine, respectively (NS).'] Do intravenous glargine and regular insulin have similar effects on endogenous glucose output and peripheral activation/deactivation kinetic profiles?