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A need for laxatives doesn’t mean there’s a bowel obstruction. People who are seriously ill often have trouble with bowel function. Laxatives are used to treat this before it has a chance to create a bowel obstruction.

Two main reasons why a person who’s ill may need a laxative are:

• Some cancers affect how the bowel works. Any tumor located near the bowel may press on it and make it difficult for the bowel to work properly. For example, ovarian cancer may do this because the ovaries are located near the bowel.
• Many medications affect how the bowel works. For example, opioid medications, such as morphine or Dilaudid, cause the bowel to slow down and not work well. Someone taking such medications needs to take a laxative also, in order to promote bowel movement.

As long as someone is passing regularly formed stools (stool consistency unchanged), and reasonably frequently (at least every three days), then it’s unlikely that person has a blocked bowel. A bowel obstruction produces abdominal pain that’s different from pain related to the underlying illness. It also produces nausea. The person is unlikely to pass any stool at all. At times there may be diarrhea or loose stool, as this can pass around a blockage. X-rays are often used to determine if someone has a bowel obstruction.

It’s important to contact a health care provider immediately if any of these symptoms appear:

• no bowel movement within three days;
• unusually high number of stools per day;
• blood in the urine, stool or anal area;
• no bowel movement within one day of taking a laxative;
• persistent cramps and vomiting.

Sennosides is a mixture of two naturally occurring plant glycosides (sennosides A and B). It works in the large intestine, acting directly on the submucosal plexus and the deeper myenteric plexus to stimulate propulsive waves. The typical onset of action for sennosides is 6―12 hours. Ideally, it should be taken at bedtime, with an expectation of results after breakfast the following morning.

Reference

Twycross R, Wilcock A, Dean M. Canadian Palliative Care Formulary. 1st Canadian ed. Nottingham, UK: Palliativedrugs.com; 2010.

Polyethylene glycol (PEG) is an osmotic laxative. It acts by absorbing more moisture into the stool, increasing the fecal volume, and inducing a laxative effect. The typical onset of action for Miralax is 1―2 days for constipation and 1―3 days for fecal impaction. It is contraindicated in severe inflammatory intestinal conditions and intestinal obstruction.

Reference

Twycross R, Wilcock A, Dean M. Canadian Palliative Care Formulary, 1st Canadian ed. Nottingham, UK: Palliativedrugs.com; 2010.