Safety of enteral naloxone for the reversal of opiate-induced constipation in the intensive care unit

Background: Opiates are the mainstay of analgesia in the intensive care unit (ICU). Unfortunately, constipation is a common adverse effect associated with opioid use. Naloxone is a pure opiate antagonist that is frequently utilized in practice for the prophylaxis or treatment of opiate-induced constipation in the ICU. Despite extensive first pass metabolism in the liver there remains the potential for opiate reversal after oral administration. We sought to assess the safety of enteral naloxone in the ICU for the treatment of opiate-induced constipation. Methods: Patients who were ordered enteral naloxone while in the ICU were identified through the Pharmacy's computer system. Patients were included in the data analysis if they had received at least one dose of enteral naloxone and had received standing opiates for at least 48 h prior to the initial naloxone dose. Patients were excluded from data analysis if the Richmond agitation-sedation scale (RASS) score was not utilized, they were paralysed or the medical record indicated that extubation was planned within the following 24 h. Data points were recorder at the following times with respect to each naloxone dose administered; time -2, -1, 0, 1, 2 and 4 h. The following data points were collected before and after each naloxone dose; blood pressure, heart rate, respiratory rate, RASS score, pain assessment score (recorded as present or absent), midazolam dose, propofol dose and fentanyl dose. In order to assess for possible opiate reversal the peak fentanyl, propofol and midazolam dose, vital sign value, RASS score and pain score were compared before and after each dose of naloxone. Results: The mean naloxone dose was 3.6 +/- 0.9 mg. There was no significant change in RASS score around the naloxone doses, -2.9 +/- 1.4 before and -2.8 +/- 1.6 after (P = 0.28). There were no significant changes in mean fentanyl, propofol or midazolam dose around naloxone administration. There were also no significant changes in heart rate, blood pressure and respiratory rate or in the presence of pain. Conclusion: These results demonstrate that the administration of enteral naloxone to patients on intravenous opiates in the ICU setting was not associated with changes in sedation score, vital signs, fentanyl dose, midazolam dose or propofol dose.