Bioavailability in vivo of naltrexone following transbuccal administration by an electronically-controlled intraoral device: A trial on pigs.

Abstract

Naltrexone (NLX), an opioid antagonist, is widely used in the treatment of opiate addiction, alcoholism and smoking cessation. Its current peroral administration induces various adverse side effects and has limited efficacy since bioavailability and patient compliance are poor. The development of a long-acting drug delivery system of NLX may overcome the current drawbacks and help in the improvement of treatment of addiction. The primary endpoints of this study were: a) to compare the NLX bioavailability and pharmacokinetics after delivering a single transbuccal dose, released by a prototype of intraoral device, versus an intravenous (I.V.) bolus of the same drug dose; b) to verify the functioning of a prototype of a new intraoral device in vivo; c) to evaluate the permeation enhancement effect of iontophoresis; d) to assess any histomorphological changes in the buccal mucosa after transbuccal delivery. The system was tested on 6 pigs in a cross-over trial. Venous blood samples were drawn at a fixed timetable from the beginning of drug administration and analyzed for the presence of NLX, using an LC/MS/MS method. A punch biopsy was performed for histological analysis after the final experiment. The administration of I.V. NLX induced a sharp increase in blood levels after 5 min and then a steep decrease. In contrast, transmucosal delivery resulted in a gradual increase in blood NLX levels, reaching its peak after 90 min, followed by a slow decrease. After 6 h the blood levels of NLX delivered through the buccal mucosa were higher as compared to I.V. administration. No signs of flogosis or tissue damage were histologically highlighted. These results suggest that buccal delivery by an intraoral electronic device could potentially induce long-lasting, continuous and controlled blood levels of NLX, avoiding at the same time spikes of drug plasma levels typical of the I.V. administration route.