title: Characterization of abdominal pain during methylnaltrexone treatment of opioid-induced constipation in advanced illness: a post hoc analysis of two clinical trials.
abstract: BACKGROUND
  Methylnaltrexone is a selective peripherally acting mu-opioid receptor antagonist that decreases the constipating effects of opioids without affecting centrally mediated analgesia. In two double-blind, placebo-controlled, Phase III studies of methylnaltrexone for opioid-induced constipation in patients with advanced illness, abdominal pain was the most common adverse event (AE) reported.
  
  
  OBJECTIVE
  This analysis sought to further characterize the Medical Dictionary for Regulatory Activities-defined abdominal pain AEs experienced in these studies.
  
  
  METHODS
  A post hoc analysis of verbatim descriptions was used to further assess AEs characterized as abdominal pain in both trials. Descriptive summary statistics were used to assess severity of abdominal pain, effect of abdominal pain on global pain scores, and other characteristics. Logistic regression analysis was used to determine the association of baseline characteristics with abdominal pain.
  
  
  RESULTS
  Most verbatim descriptions of abdominal pain referred to "abdominal cramps" or "cramping." Abdominal pain AEs were mostly mild to moderate in severity and did not affect patients' global evaluation of pain. The incidence of abdominal pain AEs in methylnaltrexone-treated patients was greatest after the first dose and decreased with subsequent doses. No association between abdominal pain AEs and most baseline patient characteristics was noted.
  
  
  CONCLUSIONS
  Abdominal pain AEs in methylnaltrexone-treated patients in clinical trials are usually described as "cramps" or "cramping," are mostly mild to moderate in severity, and decrease in incidence with subsequent dosing.
authors: California Cancer Specialists Medical Group, Monrovia, California, USA.
authors: Neal E
authors: NE
authors: Slatkin
authors: Richard
authors: R
authors: Lynn
authors: Chinyu
authors: C
authors: Su
authors: Wenjin
authors: W
authors: Wang
authors: Robert J
authors: RJ
authors: Israel
mesh_terms: D015746:Abdominal Pain / Q000139:chemically induced*; D000328:Adult; D000368:Aged; D000701:Analgesics, Opioid / Q000009:adverse effects; D003085:Colic / Q000139:chemically induced; D003248:Constipation / Q000139:chemically induced* / Q000188:drug therapy*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009271:Naltrexone / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000627:therapeutic use; D009292:Narcotic Antagonists / Q000009:adverse effects* / Q000627:therapeutic use*; D010147:Pain Measurement; D000644:Quaternary Ammonium Compounds / Q000009:adverse effects / Q000627:therapeutic use
chemical_list: D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D000644:Quaternary Ammonium Compounds; C032257:methylnaltrexone; D009271:Naltrexone