Monday, March 26, 2012
This is the first in a series of 41 posts from both GeriPal and Pallimed to get our physician readers ready for the hospice and palliative medicine boards. Every week GeriPal and Pallimed will alternate publishing a new question, as well as a discussion of possible answers to the question (click here for the full list of questions).We welcome comments about any aspects of the questions or the answers/discussions. The feedback that we hope to get in the comment sections of the post will help us all learn important aspects for the boards. We also welcome an interdisciplinary viewpoint when answering these questions, so even if you are not taking the medical boards, your input is still very much welcome.
Walking into a room at your hospice inpatient unit you see a tired appearing female patient lying in bed with soft moaning, holding her abdomen. She has end stage CHF and no history of cancer. Review of your notes show decreasing oral intake and increased time in bed. Her nurse reports she disimpacted her yesterday after suppositories and enemas were ineffective for worsening constipation.
Medications include: Fentanyl 50mcg patch (on for several weeks), Senna 2 tabs BID, Colace daily, Recent enema, and docusate suppository
Exam: Cachectic female, Scaphoid abdomen, hypoactive bowel sounds, formed (but not hard) stool on rectal exam.
What is the next best step?
a) Write an order for methylnaltrexone 8mg subcutaneously x1 now.
b) Switch her from a fentanyl patch to a morphine pump so you can better manage her abdominal pain.
c) Write an order for octreotide 200mcg subcutaneously twice daily for three days.
d) Place an NG and give her polyethylene glycol daily until she has a bowel movement or regains ability to swallow and you can remove the NG tube
Answer and Discussion:
The correct answer is A
a) The patient likely has opioid induced constipation (OIC). Methylnaltrexone is a mu-opioid receptor antagonist and is related to naloxone. After ruling out bowel obstruction, fecal impaction and any other abdominal process, you give methylnaltrexone at 0.15mg/kg subcutaneously, usually 8 (patients < 136lbs) or 12 mg (patients over 136lbs). About 60 percent of patients will have a BM in under 4 hours. Usually within 30 minutes of the first dose. Number needed to treat was 2.2 (pretty darn good). One barrier is cost. At $48 per 8mg dose this is a costly way to manage constipation.
b) While controlling abdominal pain is important relieving the cause of the abdominal pain takes precedence. Opioids may be the cause of her pain – increasing them is not indicated. With the exception of imminently dying patients, proper treatment of OIC will lead to its resolution and function can be improved.
c) Octreotide has a role in palliative care for malignant bowel obstruction (MBO), not constipation. This patient does not have a cancer history and sudden onset nausea and vomiting that may be signs for a MBO. Octreotide also is expensive-costing between $40 and $80 per dose.
d) Placing a nasogastric tube should be avoided whenever possible when there are less invasive measures available. The patient can swallow oral laxatives, and does not have an MBO and so does not have any minimal indications for an NGT in any case. Polyethylene glycol is helpful as an osmotic laxative and is often employed as a first line option for OIC. It is often more helpful as part of a maintenance regimen or for mild to moderate constipation.
- Thomas, Jay et. al. Methylnaltrexone for Opioid Induced Constipation in Advanced Illness. 2008. NEJM 358 (22): 2332-2343.
- Yuan, Chun-Su. Methylnaltrexone Mechanisms of Action and Effects on Opioid Bowel Dysfuction and Other Opioid Adverse Side Effects. The Annals of Pharmacotherapy, 2007. 41: 984- 993
(For email readers - click here for full post to see the answer and discussion)