Abstracts of Posters Presented at the International Anesthesia Research Society; 72nd Clinical and Scientific Congress; Orlando, FL; March 7-11, 1998: Anesthesia/OR Economics
Constipation is the most common side effect of opioids and can be a severe problem in those patients taking opioids chronically for pain therapy. We studied the gut motility and transit time in methadone-maintained addicts and in normal subjects by measuring oral-cecal transit time.
Methods: With approval from the IRB, 9 males and 10 females who had been in a methadone maintenance program for at least 1 month were enrolled in this study. Their mean age +/- SD (range) was 37.2 +/- 8.0 (26-56) years. The subjects were admitted in the morning for a study which lasted approximately 5 hr. Gastrointestinal transit time was assessed by the lactulose hydrogen breath test. Subjects were also asked to complete a questionnaire regarding their bowel activity. Oral-cecal transit times in the subjects were compared to transit times recorded previously in two studies of non-addict volunteers. The Wilcoxon matched pairs signed rank test was used for statistical analysis.
Results: Mean oral-cecal transit time +/- SD of the methadone-maintained subjects was 159 +/- 49.2 min, significantly longer than the transit time recorded in two previous studies of non-addicted subjects (105 +/- 31 min and 114 +/- 37 min, respectively; P < 0.01) (Figure 1) None of the subjects taking methadone reported constipation problems before usage of illicit drugs. During chronic methadone therapy, 58% of subjects experienced some degree of constipation, and two of the 19 subjects reported that constipation was a very serious problem.
Conclusion: Our results indicate that tolerance to opioids does not appear to extend to gastrointestinal motility and transit. It has been shown that constipation is the most common side effect of chronic opioid pain medication in patients with metastatic malignancy. Before proceeding to treat chronically ill cancer patients with methylnaltrexone, a peripheral opioid receptor antagonist, we intend to evaluate its effects in subjects undergoing methadone therapy.