Use of Methylnaltrexone for Refractory Opioid-Induced Constipation in Children

Marcia L. Buck, Pharm.D., FCCP, FPPAG


Pediatr Pharm. 2014;20(3) 

In This Article


Opioid-induced constipation (OIC) remains one of the most difficult to manage adverse effects of chronic pain management in children and adults. The incidence of OIC has been reported to be as high as 57% of adults receiving opioids for chronic pain and 94% of patient receiving palliative care. Activity of opioid analgesics at mu-opioid receptors in the gastrointestinal tract lead to a number of physiologic changes, including decreased gut motility, increased fluid absorption from the gut along with decreased intestinal secretions, increased sphincter tone, and a reduced sensitivity to colonic distension. This combination of changes in GI function can produce constipation that often fails to improve with administration of standard laxatives.[1–3]

For many years, clinicians caring for patients with OIC have utilized low doses of naloxone, an opioid antagonist, given orally to counteract the effects of opioids on the GI tract.[4] While often effective, the lack of an oral dosage form and the short duration of effect makes this therapy less than ideal. In 2008, the Food and Drug Administration approved subcutaneous methylnaltrexone for the treatment of OIC in adults with advanced illness who are receiving palliative care and have not responded to laxative therapy.[2] Although not yet approved for use in children, several recent reports suggest a potential role for methylnaltrexone in pediatric OIC associated with opioid use for cancer or postoperative pain.