7-DAY ANTINOCICEPTIVE EFFECT OF A SUSTAINED-RELEASE VAPREOTIDE FORMULATION

THIS work studies the antinociceptive effect of a sustained (7 day) re lease 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 ant inociceptive effect for 7 complete days with a maximal increase in voc alization 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 opi oidergic involvement throughout the antinociceptive effect. These find ings suggest potential interest in human therapy.