Abstract
AIMS/INTRODUCTION: Many patients with diabetes now use 5-, 6- or 8-mm needles for insulin injection. However, it is unclear whether needle length, particularly for shorter needles, affects the pharmacokinetic properties of insulin. MATERIALS AND METHODS: This was a three-way, randomized, cross-over, single-center study involving 12 healthy Japanese adult males (age 27.4 ± 4.14 years; weight 64.2 ± 5.2 kg; body fat percentage 18.2 ± 1.5%). Participants received a subcutaneous (abdomen) dose of insulin lispro (1.5 U for participants weighing 55 to <65.0 kg; 2.0 U for participants weighing 65.0 to <80.0 kg) delivered using a 32-G × 4 mm (32G × 4), 31-G × 8 mm (31G × 8) or 32-G × 6 mm (32G × 6) needle with a 3-7-day washout between doses. Pharmacokinetic parameters of exogenous insulin were identified using non-linear least squares, where the total insulin concentration was fit to the measured plasma insulin concentration using an overall combined model that accounted for C-peptide/insulin secretion in addition to the injected dose. RESULTS: Maximum concentration and area under the curve for 0 to infinity min for insulin were bioequivalent for the 32G × 4 needle relative to the 32G × 6 and the 31G × 8 needles. The time to the maximum insulin concentration was bioequivalent for the 32G × 4 needle relative to the 32G × 6 needle, but not the 31G × 8 needle. CONCLUSIONS: The use of 4-mm needles is unlikely to change the pharmacokinetic properties of insulin when injected subcutaneously in adults. This trial was registered with UMIN-CTR (no. UMIN000004469).