 Treatments will be administered in a double-dummy manner. Identical bottles of Sativex and placebo should be obtained from the manufacturer GW Pharmaceuticals. Identical prefilled vials containing either the active placebo 1 mg midazolam 1 g acetaminophen or sodium chloride 0.9 should be prepared by the hospital pharmacist. To the best of our knowledge, no clinical studies evaluating the effects of nabiximols on acute pain or in a perioperative setting have been done to date. Therefore, the investigators estimate a Sativex dose range that seems reasonable to obtain relevant clinical and a manageable occurrence of adverse events, mainly based on the recommendations from the manufacturer, on the available pharmacological data presented in the previous section and on the results of other clinical trials with a similar design using comparable doses of oral THC. Nevertheless, the first 10 patients will be randomly assigned either to the nabiximols low dose group or to the placebo control group only. The investigators will proceed with the full four-group randomization only if no serious adverse events are registered among the 10 first recruited patients. 