Oral Naloxone for Methadone-induced Constipation: Preliminary Results of a Randomized Placebo-controlled Trial

IntroductionConstipation is a very common and one of the most persistent side effects of opioids. In many cases constipation causes severe discomfort and puts limitations on methadone maintenance treatment (MMT). Conventional laxatives are not always effective and do not address the pathophysiological basis of constipation. It was suggested that opioid receptor antagonists with low oral bioavailability e.g. naloxone might reverse constipation while not affecting the course of MMT.The aim of the study is to assess the feasibility and effectiveness of oral naloxone for methadone-induced constipation in MMT patients.Objectives 1.To assess the changes in bowel functioning in constipated patients receiving oral naloxone2.To describe the opioid withdrawal symptoms due to oral naloxone administration3.To evaluate the changes in quality of life in patients receiving oral naloxoneMethodsRandomized placebo-controlled trial (n=20).ResultsFive patients were enrolled into the study. All of them completed the 16-day study protocol. Mild opioid withdrawal symptoms (perspiration) that lasted for several hours were observed once in 3 out of 5 patients and did not affect the MMT. Constipation reversal was achieved in 4 out of 5 patients as well as significant reduction of laxative use. Over the course of the study substantial improvement in quality of life was observed in those patients whose constipation was relieved.ConclusionsThe preliminary results indicate that oral naloxone is a feasible treatment for constipation in MMT patients. Definite conclusions and evaluation of placebo effects will be possible after completion of the study and unblinding.