Aside from the challenge of treating their patients’ actual cancer, oncologists frequently encounter side effects secondary to their patients’ medications or actual disease process.

Constipation is a common complaint of many patients with cancer, which can be difficult to manage both on an in-patient and out-patient basis.  Constipation has several different definitions; however, a common definition is for bowel movements to occur less than three times per week.1,2 As the frequency of bowel movements can be highly variable from patient to patient, the “normal” frequency for a particular patient should be confirmed during their examination. 

There is a broad differential diagnosis for constipation in a patient with cancer, with some of the more common causes including dietary and electrolyte abnormalities (such as hypokalemia and hypercalcemia), medications, primary or secondary involvement of their cancer, and relative immobility. 

Constipation secondary to opioids is unique in that tolerance does not develop; therefore a steady bowel regimen from the start is a vital part of the patient’s management.  Since chronic pain is often a problem in patients with cancer, those taking both short-term and long-term narcotics should be placed on a bowel regimen upon initiation of these medications.

RELATED: The Importance of Proper Nutrition for Patients During Cancer Care

Aside from opioids, medications that can contribute to constipation include iron supplements, antidepressants with anticholinergic properties (e.g., tricyclic antidepressants), and 5-HT3 receptor blockers.  Chemotherapeutic agents associated with constipation include the vinca alkaloids (i.e., vinblastine and vincristine), bortezomib, busulfan, and thalidomide. 

A detailed history and physical exam can help provide clues as to the source of the constipation.  Assuming there are no contraindications, such as neutropenia, a rectal exam is crucial to rule out impaction.  Once a complete work-up is completed and the appropriate diagnosis has been made, there are several approaches that can be taken to help with the patient’s constipation.

There are numerous medications available, both over-the-counter and prescription, to treat constipation. The medications reviewed here are for use in patients with the appropriate diagnosis and source of constipation and are not meant to be used in every patient who experiences constipation. For example, patients with cancer who have small bowel obstructions would not benefit from high-dose laxatives and would require other interventions to relieve their constipation. 

Basic dietary changes such as increasing the amount of dietary fiber with supplements (e.g., psyllium and methylcellulose) is a potential first step in treating constipation.  These supplements typically take several days to work, so an immediate result should not be expected. Psyllium and methylcellulose can also interfere with the absorption of medications such as warfarin and digoxin; consequently, close monitoring for potential decreased efficacy should be performed.  Increased hydration is often recommended with these products, which may be difficult in a patient with advanced cancer or those with compromised oral access.

Stool softeners, such as docusate, are frequently combined with stimulant laxatives (e.g., senna, bisacodyl) as first-line therapy for constipation, especially in opioid-induced cases. Docusate and senna are available in liquid form, whereas bisacodyl is available as an oral tablet and suppository. These may be helpful for patients who have difficulty swallowing pills.

The osmotic laxatives, lactulose, sorbitol, or polyethylene glycol, can also be added to a patient’s bowel regimen. Lactulose and sorbitol frequently cause abdominal bloating and cramping, which may further complicate a patient’s gastrointestinal symptoms.

Metoclopramide is sometimes used as a last-line treatment in patients who do not respond to the previously mentioned regimens. As a prokinetic agent, metoclopramide blocks dopamine receptors, which can lead to the development of extrapyramidal symptoms with higher, more frequent doses. The routine use of metoclopramide for constipation is not recommended and should only be considered in limited use with close neurological monitoring.

Managing constipation in patients with cancer can be a difficult process; the appropriate regimen can be highly variable based on the patient’s co-morbidities and other symptoms.  A patient’s nutritional status should also be monitored, since overtreating constipation can lead to dehydration and additional sequelae.


References

  1. Bharucha AE, Pemberton JH, Locke GR. American Gastroenterological Association technical review on constipation.  Gastroenterology. 2013;144:218-238.
  2. Bharucha AE, Spencer DD, Lembo A, et al. American Gastroenterological Association medical position statement on constipation. Gastroenterology. 2013;144:211-217.