Intradermal Microneedle Delivery of Insulin Lispro Achieves Faster Insulin Absorption and Insulin Action than Subcutaneous Injection

Background: This study compared insulin lispro (IL) pharmacokinetics (PK) and pharmacodynamics (PD) delivered via microneedle intradermal (ID) injection with subcutaneous (SC) injection under euglycemic glucose clamp conditions. Methods: Ten healthy male volunteers were administered 10 international units (IU) of IL at 3 microneedle lengths (1.25, 1.50, or 1.75 mm) in a randomized, crossover fashion on Days 1–3 followed by a repetitive ID 1.5-mm microneedle dose (Day 4) and an SC dose (Day 5). Results: Microneedle ID delivery resulted in more rapid absorption of IL, with decreased time to maximum insulin concentration (ID vs. SC: 36.0–46.4 vs. 64.3 min, P < 0.05) and higher fractional availability at early postinjection times. ID produced more rapid effects on glucose uptake with shorter times to maximal and early half-maximal glucose infusion rates (GIRs) (ID vs. SC: time to maximum GIR, 106–112 vs. 130 min, P < 0.05; early half-maximal GIR, 29–35 vs. 42 min), increased early GIR area under the curve (AUC), and faster offset of insulin action (shorter time to late half-maximal GIR: 271–287 vs. 309 min). Relative total insulin bioavailability (AUC to 360 min and AUC to infinite measurement) did not significantly differ between administration routes. ID PK/PD parameters showed some variation as a function of needle length. Delivery of ID IL was generally well tolerated, although transient, localized wheal formation and redness were observed at injection sites. Conclusions: Microneedle ID insulin lispro delivery enables more rapid onset and offset of metabolic effect than SC therapy and is safe and well tolerated; further study for insulin therapy is warranted.