INVESTIGATION OF THE PHARMACOKINETICS AND ANALGESIC EFFECTS OF AN INTRAMUSCULAR INJECTION OF SUSTAINED-RELEASE SUFENTANIL FOR POSTOPERATIVEPAIN - AN OPEN STUDY

Study Objectives: To investigate the pharmacokinetics after an intramu scular (IM) injection of sufentanil in thin vegetable oil in postsurgi cal patients and to deretmine whether sustained-release IM sufentanil can provide safe and sufficient analgesia of lans duration in these pa tients. Design: Open study. Setting: University hospital. Patients: 10 ASA physical status land II patients aged 18 to 65 years who were sch eduled for elective surgery. Interventions: All patients were premedic ated with lorazepam and anesthetized with a general anesthetic techniq ue containing nitrous oxide, fentanyl, and isoflurane. As soon as sign ificant pain [visual analog scale score of 5 or greater (range, 0 = no pain to 10 = worst pain imaginable)] occurred during the early postop erative period the patient received an IM injection of sustained-relea se sufentanil. Measurements and Main Results: During the first 48 hour s following surgery, blood samples were taken for determination of pla sma sufentanil concentrations. Blood pressure, heart rate, respiratory rate, pain scores, and sedation scores were documented at the same ti me. The IM administration of sufentanil in thin vegetable oil provided sufficient pain relief although the onset of analgesia was rather slo w (+/- I hour). The analgesic effect was still apparent 48 hours later Plasma concentration of sufentanil at the different time points varie d from 0.021 to 0.142 ng/ml, with a mean maximal peak concentration of 0.103 ng/ml. The plasma concentration 48 hours after injection varied from 0.026 to 0.074 ng/ml. Conclusions: Although an IM injection of s ufentanil in thin vegetable oil is effective for postoperative pain re lief it is associated with wide interindividual variability in plasma concentration of sufentanil and long duration of action.