Effect of subcutaneous methylnaltrexone on patient-reported constipation
symptoms.
Author(s): Iyer SS, Randazzo BP, Tzanis EL, Schulman SL, Zhang H, Wang W, Manley AL.
Affiliation(s): Pfizer Inc, Collegeville, PA, USA. shrividya.iyer@pfizer.com
Publication date & source: 2011, Value Health. , 14(1):177-83
BACKGROUND: Methylnaltrexone, a selective peripheral acting mu-opioid receptor
antagonist, alleviates the constipating effects of opioids without affecting
centrally mediated analgesia.
OBJECTIVES: To assess the effect of subcutaneous (SC) methylnaltrexone injection
on patient-reported constipation symptoms and pain scores.
METHODS: A total of 469 subjects on opioids for chronic non-malignant pain with
opioid-induced constipation were randomized to methylnaltrexone SC with once
daily (QD) or every other day (QOD) dosing or placebo for 4 weeks. Constipation
symptoms and pain were assessed using the patient assessment of
constipation-symptoms (PAC-SYM) questionnaire and a 11-point scale, respectively,
at baseline, Day 14 and Day 28. Change from baseline in PAC-SYM and pain scores
were compared between methylnaltrexone and placebo arms at Day 28 using analysis
of covariance, with treatment group as factor and baseline score as covariate.
RESULTS: A majority of patients were women (60%), average age was 49 years old,
and back pain (60%) was the primary pain condition. At Day 28, the
methylnaltrexone SC QD group showed a significant improvement over placebo for
rectal symptoms (-0.56 vs. -0.30; P < 0.05), stool symptoms (-0.76 vs. -0.43; P <
0.001) and global scores (-0.62 vs. -0.37; P < 0.001). Improvement in stool
symptoms (-0.69 vs.-0.43; P < 0.05) and the global scores (-0.52 vs. -0.37; P <
0.05) were significantly greater than placebo in the methylnaltrexone QOD group.
Differences in change from baseline in abdominal symptoms and pain scores between
the methylnaltrexone SC QD or QOD dosing arms and placebo were not significant.
CONCLUSION: The results of our study indicate significant improvement in
constipation symptoms with methylnaltrexone QD or QOD dosing compared to placebo
without a significant effect on pain scores.
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