Adverse events in the removal of naltrexone implants

Naltrexone implants are used as an abstinence therapy for patients with opioid, amphetamine and alcohol abuse. This study was designed to assess the implications of this therapy in patients presenting for anaesthesia for removal of these implants. We conducted a retrospective case-note review of 37 patients undergoing removal of naltrexone implants in the period 2001 to 2008 at Sir Charles Gairdner Hospital. Indications for removal included infection at the insertion site, naltrexone intolerance or the requirement for effective opioid analgesia. Thirty-two patients had surgery under general anaesthesia, four under local anaesthesia and one under spinal anaesthesia. The perioperative opioid requirement varied from 0 to 100 mg of intravenous morphine equivalents (median 11.7 mg, mean 20.7 mg). The only factor that was associated with a higher perioperative opioid requirement was whether the implant was infected or not. Forty-four percent of patients having a general anaesthetic complained of moderate to severe pain postoperatively, and 64% of these patients had a prolonged stay in the post-anaesthesia care unit. We did not observe any instances of postoperative complications due to increased opioid sensitivity after removal of naltrexone implants. The majority of patients were discharged home by the first postoperative day. Anaesthesia for the removal of naltrexone implants was associated with a wide range of opioid analgesia requirements and a high incidence of pain postoperatively. Concern regarding increasing opioid sensitivity after removal of implants does not seem to preclude use of generous opioid analgesia in this group of patients.