The first step (single-blind standard group) aims to verify the sensitivity of the study pain model in the proposed surgery to confirm the validity of the surgery according to their pain and enrolment rate. 12 patients are planned to be enrolled.~The second step (dose-finding study) is a randomized, double-blind, parallel groups, controlled clinical trial involving a total of 106 patients divided into two groups in which patients will be randomized between STR-324 and morphine HCl:~Group 1: Titration initiated with a bolus~Group 2: Titration without initial bolus.
This study aims to evaluate the analgesic effect and the safety of 4 doses of STR-324 administered as an infusion, with or without initial bolus, to patients suffering from post-operative pain.~The sensitivity of the pain model used in the trial will be evaluated with a standard group treated with morphine under the usual care conditions.