Background: Exenatide (synthetic exendin-4;AC2993) is a 39-amino acid peptide in the new class of antidiabetic agents known as incretin mimetics. In clinical trials, exenatide exhibited glucoregulatory effects (glucose-dependent stimulation of insulin secretion, suppression of inappropriately elevated glucagon secretion, slowing of gastric emptying) in patients with type 2 diabetes mellitus (DM).
Objective: The goal of this study was to determine the relative bioavailability of exenatide injected subcutaneously into the abdomen, arm, or thigh.
Methods: Patients with type 2 DM were randomized in an open-label, crossover study to assess relative bioavailability of exenatide (10 microg) injected into the arm and thigh versus injection into the abdomen. Serial plasma exenatide concentrations were measured for 10 hours after injection. A sample size of >24 patients provided approximately 80% power to ensure that 90% CIs were within the 80% to 125% interval for the ratios (geometric least squares [LS] means) of AUC(0-infinity).
Results: Twenty-eight patients were randomized into the study (mean age, 56  years; glycosylated hemoglobin, 8.0 [1.7]%; body mass index, 33  kg/m2; all values given as mean [SD]). AUC(0-infinity) values (geometric LS mean SE for SC injections into the abdomen arm and thigh were 63,935 (6608), 59,573 (6157), and 62,148 (6424) pg./mL, respectively. The AUC (geometric LS mean ratio for relative bioavailability) for arm versus abdomen was 0.93 (geometric 90% CI, 0.82-1.05); for thigh versus abdomen it was 0.97 (geometric 90% CI, 0.86-1.10). Consistent with the observed data, intrasubject variability of AUC(0-infinity) was low among the 3 treatments (coefficient of variation, 26%). C(max) values (geometric LS mean [SE]) were 220 (24) pg/mL, abdomen; 218 (23) pg/mL, arm; and 193 (21) pg/mL, thigh. The C(max) (geometric LS mean ratio) for arm versus abdomen was 0.99 (geometric 90% CI, 0.85-1.15), and for thigh versus abdomen it was 0.88 (geometric 90% CI, 0.75-1.02). The most common treatment-emergent adverse events were mild to moderate nausea (36%), headache (25%), vomiting (21%), and dizziness (18%). Three patients received an inadvertent 10-fold overdose and were withdrawn from the study immediately. All experienced severe nausea and vomiting, and 1 patient experienced severe hypoglycemia requiring aid. All recovered without mishap and were excluded from statistical and tolerability results. There were no adverse events related to the injection or the injection site.
Conclusion: In this study of patients with type 2DM, SC administration of exenatide into the abdomen, arm, or thigh resulted in comparable bioavailability.