Unmodified regular insulin has a long absorption tail, unlike the fast-acting insulin analog lispro, and may contribute to hypoglycemia in the early part of the night. A randomized crossover double-blind study was performed to compare blood glucose concentrations in the early part of the night in type 1 diabetic patients receiving lispro or unmodified regular human insulin, in random order, on 2 separate study days.
We studied 23 C-peptide-negative patients; 12 were using a premeal plus basal insulin regimen, and 11 were using twice-daily insulin injections. Patients were admitted to the investigation unit at 5:00 P.M. and received a single dose of lispro or unmodified regular human insulin before the evening meal. In both groups, the NPH insulin dose remained unchanged. Identical meals and snacks were eaten at the same time during both study days.
Average postprandial (6:00−10:00 P.M.) blood glucose concentrations were significantly lower after lispro therapy compared with human insulin (7.1 ± 0.4 [SE] vs. 8.5 ± 0.4 mmol/l, P = 0.0002). Nighttime (midnight to 4:00 A.M.) blood glucose concentrations were significantly higher after lispro compared with human insulin (10.3 ± 0.4 vs. 9.1 ± 0.4 mmol/l, P = 0.02). This difference was greatest in patients on the premeal plus basal insulin regimen (11.6 ± 0.5 vs. 8.7 ± 0.4 mmol/l, P < 0.001). The incidence of nocturnal hypoglycemia (midnight to 4:00 A.M., blood glucose < 3.5 mmol/l) was less with lispro compared with unmodified insulin (1 vs. 6 patients, P = 0.04). Nighttime (midnight to 4:00 A.M.) 3-hydroxybutyrate (102 ± 13 vs. 51 ± 7 mumol/l, P = 0.000) and glycerol (52 ± 3 vs. 42 ± 2 mumol/l, P < 0.01) were significantly higher after lispro therapy compared with human insulin in patients on the premeal plus bolus insulin regimen.
Lispro can improve postprandial blood glucose control and reduce the incidence of nocturnal hypoglycemia at the expense of nocturnal hyperglycemia and hyperketonemia in patients using a premeal plus basal insulin regimen.