A 72-year-old man is evaluated for refractory constipation. He recently had an episode of stool impaction requiring manual disimpaction and is now passing flatus and small amounts of hard stool. He has no abdominal pain, vomiting, or hematochezia. The patient is receiving palliative care for stage IV lung cancer with multiple skeletal metastases and has adequate pain control with a fentanyl patch and oral immediate-release morphine. His other medications include a fiber supplement, senna-docusate combination, and oral lactulose.
Examination shows a frail-looking, cachectic man. Bowel sounds are normal. His abdomen is soft, nondistended, and nontender.
Which of the following is the most appropriate next step in managing this patient's constipation?

Question

A 72-year-old man is evaluated for refractory constipation.  He recently had an episode of stool impaction requiring manual disimpaction and is now passing flatus and small amounts of hard stool.  He has no abdominal pain, vomiting, or hematochezia.  The patient is receiving palliative care for stage IV lung cancer with multiple skeletal metastases and has adequate pain control with a fentanyl patch and oral immediate-release morphine.  His other medications include a fiber supplement, senna-docusate combination, and oral lactulose.
Examination shows a frail-looking, cachectic man.  Bowel sounds are normal.  His abdomen is soft, nondistended, and nontender.
Which of the following is the most appropriate next step in managing this patient's constipation?

Quizplus · Accepted Answer

Patients with opioid-induced constipation can be managed initially by increasing fluid and dietary fiber intake and physical activity. Pharmacotherapy with daily senna-docusate or an osmotic laxative (eg, polyethylene glycol, lactulose) may also be effective. Those who have refractory constipation despite these measures can significantly improve with subcutaneous methylnaltrexone, a peripherally acting opioid antagonist that does not cross the blood-brain barrier and does not cause opiate withdrawal symptoms. Methylnaltrexone should be used cautiously in patients with gastrointestinal lesions associated with reduced structural integrity (eg, malignancy, peptic ulcer disease, diverticular disease) as severe abdominal pain and bowel perforation have been observed. The medication should be discontinued immediately if abdominal pain worsens. (Choice B) Mineral oil enemas can help evacuate the colon in patients with fecal impaction; however, this patient has already undergone manual disimpaction and is passing flatus with hard stool. In addition, his opioid-induced constipation is refractory to first-line interventions and will likely respond best to methylnaltrexone. (Choices C and D) Discontinuation of fentanyl patch is not necessary as the medication is adequately controlling this patient's pain and may have fewer constipating effects compared to other opioid analgesics (eg, slow-release oral morphine). Switching from morphine to hydromorphone is also unlikely to benefit this patient as these medications are equally constipating. (Choice E) There is very limited data supporting the use of misoprostol in the treatment of opioid-induced constipation. Educational objective: Initial management of opioid-induced constipation typically includes increasing fluid/fiber intake and physical activity in addition to therapy with daily senna-docusate or an osmotic laxative (eg, polyethylene glycol, lactulose). Refractory constipation may respond to treatment with methylnaltrexone, a peripherally acting opioid antagonist. __________ References: Methylnaltrexone: treatment for opioid-induced constipation. (http://www.ncbi.nlm.nih.gov/pubmed/20801917) Methylnaltrexone for opioid-induced constipation in advanced illness. (http://www.ncbi.nlm.nih.gov/pubmed/18509120)

A 72-Year-Old Man Is Evaluated for Refractory Constipation