Management of opioid-induced constipation in palliative care
First-line treatment for opioid-induced constipation is with stool softeners and stimulant laxatives—for dosages, see Undifferentiated constipation in palliative care.
When opioid-induced constipation becomes refractory to laxatives or if treatment becomes burdensome, methylnaltrexone (an injectable peripheral opioid antagonist that does not cross the blood–brain barrier) can be useful. It may allow discontinuation or reduction in dose of other laxatives, but should not be used if bowel obstruction is suspected. Warn patients that after administration of methylnaltrexone their bowels may move quickly with little warning; toilet facilities and assistance need to be close by. Abdominal discomfort commonly occurs after the bowels have opened. Use:
methylnaltrexone subcutaneously, as a single dose on alternate days, or at longer intervals (eg twice a week or every 3 days), as required: methylnaltrexone
adults who weigh less than 38 kg: 0.15 mg/kg
adults who weigh 38 to 61 kg: 8 mg
adults who weigh 62 to 114 kg: 12 mg
adults who weigh more than 114 kg: 0.15 mg/kg.
If methylnaltrexone is ineffective, seek specialist advice.
After constipation resolves, review the patient’s regular laxative regimen and modify if necessary, or consider starting a regular regimen to prevent recurrence.