Bioavailability and Dose Proportionality of Intramuscular Diazepam Administered by Autoinjector

A diazepam 10-mg autoinjector was evaluated in bioequivalence and dose proportionality studies; both involved 24 young, healthy subjects and used randomized, open-label, 2-treatment, 2-period crossover designs with a 3-week washout period between treatments. The bioequivalence study compared a single diazepam 10-mg autoinjector with a conventional needle and syringe containing 10 mg of diazepam injectable. The dose proportionality study compared the pharmacokinetics of a single diazepam 10-mg autoinjector with that of 2 diazepam 10-mg autoinjectors given simultaneously (20 mg). Injections were intramuscular in the midanterolateral thigh in both studies. The studies showed that the diazepam autoinjector produced consistent plasma diazepam levels, with a rapid onset of absorption. The diazepam 10-mg autoinjector given intramuscularly was bioequivalent to a conventional syringe containing diazepam 10 mg. A single (10-mg) autoinjector and 2 (20-mg) diazepam autoinjectors administered simultaneously produced plasma diazepam concentrations that were essentially dose proportional.