Methylnaltrexone may restore bowel function in critically ill patients

Promising results reported in Mayo Clinic Proceedings

Opioids are a mainstay of care in the critical care unit, but their use frequently causes constipation which can lead to adverse outcomes including delayed feeding and later discharge from the ICU. Researchers from London, UK, and Chicago, IL, have found that methylnaltrexone (MNTX), a peripheral opioid antagonist, may restore bowel function in critically ill patients. Their retrospective study appears in the March issue of Mayo Clinic Proceedings.

"We found MNTX to be very effective in producing laxation when compared with conventional laxatives in our critically ill patients. MNTX was well tolerated and did not demonstrate any signs of reversing the effects of centrally mediated analgesia or precipitate withdrawal," says lead author Parind B. Patel, MBBS, FRCA, Critical Care Medicine, Hammersmith Hospital, London. MNTX was developed at the University of Chicago by Dr. Jonathan Moss.

Researchers reviewed 88 nonsurgical critical care patients in their ICU during a 10-week period. 15 of the patients suffered from opioid induced constipation (OIC) within 72 hours of admission to the ICU. 7 were managed with MNTX and 8 were managed with conventional therapy consisting of sodium picosulfate and glycerin suppositories.

The most striking result was the immediate effect of MNTX. Laxation occurred within 24 hours in 6 of the 7 patients, compared with none of the 8 patients in the conventional therapy group. MNTX was ineffective in one patient with a large intra-abdominal hematoma. When this patient was excluded from the analysis, the MNTX-treated patients laxated within 7.8 hours vs. 96.0 hours for patients who received conventional treatment.

"We observed a clinically significant improvement in feeding and decreased gastric residual volumes in our patients with MNTX treatment," notes Dr. Patel. "Although our study was too small to demonstrate statistical significance, the improvement in enteral feeding suggests that further study is merited. The reduction in residual volumes following MNTX was dramatic and facilitated early target enteral feeding. There is a trend toward improved outcome, but our study was too small to document this statistically."

The lack of suitable therapy has hampered study of bowel function in the ICU. "Our findings demonstrate a potential role for MNTX in managing OIC in critically ill patients and suggest that a larger controlled study in the ICU environment is merited," Dr. Patel concludes.