Biovector (TM) nanoparticles improve antinociceptive efficacy of nasal morphine

Purpose. We have studied the antinociceptive activity and blood and brain d elivery of nasal morphine with or without Biovector(TM) nanoparticles in mi ce. Methods. A tail flick assay was used to evaluate the antinociceptive activi ty. The kinetics of morphine were evaluated in blood and brain, using triti ated morphine as tracer. Results. These nanoparticles were shown to increase the duration of the ant inociceptive activity of morphine after nasal administration. This effect w as not due to an increase of morphine in the blood; and the analgesic activ ity of morphine in association with nanoparticles was reversed by naloxone. The ED50 value was 33.6 +/- 15.6 mg/kg for morphine alone and 14.4 +/- 7.6 mg/kg in presence of nanoparticles. They were only effective at low doses (1.5 to 2.5 mu g), a higher or a lower dose had no effect. No interaction w as found between nanoparticles and morphine. NaDOC, a permeation enhancer, was unable to improve nasal morphine activity. Conclusions. These results show the presence of nanoparticles only at a ver y specific dose increases the antinociceptive activity of nasal morphine in mice. The occurrence of a direct transport of morphine from the nasal muco sa to the brain is discussed.