Aims: Despite considerable experience with insulin lispro, few blinded comparisons with soluble insulin are available. This study compared insulin lispro with human soluble insulin in patients with Type 1 diabetes mellitus on multiple injection therapy who inject shortly before meals.
Methods: Glucose control, frequency of hypoglycaemia and patient preference were examined in the course of a prospective, randomized, double-blind, crossover comparison, with a 6-week run-in period and 12 weeks on each therapy. Ninety-three patients took part, all on multiple daily doses of insulin, with soluble insulin before meals and NPH (isophane) insulin at night. The main outcome measures were self-monitored blood glucose profiles, glycated haemoglobin, frequency of hypoglycaemic episodes, patient satisfaction and well-being and patient preference.
Results: Blood glucose levels were significantly lower after breakfast and lunch, but higher before breakfast, lunch and supper, in patients taking insulin lispro. Levels of HbA(1c) were 7.4 +/- 1.1% on Humulin S and 7.5 +/- 1.1% on insulin lispro (P = 0.807). The overall frequency of symptomatic hypoglycaemia did not differ, but patients on insulin lispro were less likely to experience hypoglycaemia between midnight and 6 a.m., and more likely to experience episodes from 6 a.m. to midday. Questionnaires completed by 84/87 patients at the end of the study showed that 43 (51%) were able to identify each insulin correctly, nine (11%) were incorrect, and 32 (38%) were unable to tell the insulins apart. No significant preference emerged: 35 (42%) opted for insulin lispro, 24 (29%) opted for Humulin S, while the remainder had no clear preference.
Conclusions: Substitution of insulin lispro for soluble insulin in a multiple injection regimen improved post-prandial glucose control at the expense of an increase in fasting and pre-prandial glucose levels. Patients who already injected shortly before meals expressed no clear preference for the fast-acting analogue, and did not improve their overall control as a result of using it. Nocturnal hypoglycaemia was however, less frequent on insulin lispro, and may emerge as a robust indication for its use.