The Evaluation of the Effectiveness and Safety of Nalbuphine Hydrochloride Injection for Analgesia in ICU Patients: A Multicenter, Randomized, Single-blinded, Parallel, Two-step Trial

brief summary

The analgesic effect of nalbuphine hydrochloride injection will be evaluated in a multicenter, randomized, single-blind, parallel, positive-controlled approach in two steps: step 1, to explore the optimal dosage of nalbuphine hydrochloride injection with 2 experimental arms and 1 positive control and step 2, to evaluate the effectiveness and safety of nalbuphine hydrochloride injection in mechanically ventilated ICU patients at a dosage determined in step 1 with the same positive control.