Treating constipation in palliative care: the impact of other factors aside from opioids

Opioids are major contributing factors to the problem of constipation in palliative care. Whilst this is without doubt, it remains unclear how much other factors also contribute to the problem. The aim of this audit is to review what other contributing factors are present when methylnaltrexone, the peripheral opioid antagonist is prescribed for constipation. The medical records of people prescribed methylnaltrexone over a four-month period were reviewed to examine certain characteristics of people including the whether the reason for constipation was charted, whether other factors that could contribute to constipation were considered and the effectiveness of methylnaltrexone. Over the study period, 10 people received methylnaltrexone, only 4 of whom had a bowel action less than 24 hours after administration with 3 not having any bowel actions reported 6 days after administration. Whilst all were receiving opioids, the opioids doses were in the moderate range (61-200 mg morphine equivalent). However, all had other factors that could contribute to constipation including impaired functional status and medications with anti-cholinergic effects (mean anti-cholinergic load 4.5). In conclusion, methylnaltrexone is targeted treatment for the management of opioid-induced constipation. However, there is a percentage of people who fail to respond. The impact of other factors on the problem of constipation requires greater clarification.