Seven-day antinociceptive effect of a sustained release vapreotide formulation

This work studies the antinociceptive effect of a sustained (7 day) release dosage form of vapreotide, a peptidic analogue of somatostatin, in rats submitted to a nociceptive mechanical stimulus (paw pressure). One intramuscular injection (0.6 mg/animal) induced a significant antinociceptive effect for 7 complete days with a maximal increase in vocalization thresholds of 68 +/- 5% and a plateau of activity during the first 4 days. This action was totally inhibited by naloxone (1 mg kg-1, s.c.) injected 24 h or 6 days after vapreotide, suggesting an opioidergic involvement throughout the antinociceptive effect. These findings suggest potential interest in human therapy.