LAXATIVES
(see Constipation)

About 80% of hospice patients eventually need a regular laxative. Almost all patients on regular opioids need daily laxatives. As analgesic doses increase, laxative doses need to increase.

Classification of laxatives:

• Bulking agents (bran, or fiber laxatives)

• Fecal softeners (docusate sodium)

• Colonic stimulants (senna, bisacodyl, casanthrol)

• Small bowel (osmotic) flushers (weak: lactulose, strong:      magnesium sulfate)

The action of all these drugs is complex and poorly understood.

Most patients require a fecal softener plus a colonic stimulant laxative. A good regime for most patients taking opioids is Senokot-S (senna concentrate and docusate sodium) or Peri-Colace (casanthrol and docusate sodium) 1 to 3 tablets 2 times a day. A suppository or micro enema should be given on the third day if the bowels have not moved, and the dose of oral laxatives increased.

If the motions are soft but remain infrequent, give additional stimulant laxatives. If motions remain hard add a small bowel flusher (lactulose syrup 10ml to 30ml 3 times a day or magnesium sulfate 5ml to 10ml with plenty of water, in the morning).

«  Abdominal cramps can occur with stimulant or osmotic laxatives and are dose dependent.

Bran, taken with food or fruit juice, is an effective high fiber preparation. The full effect may take some days to develop. 60% of the bran is excreted (increasing the bulk by holding water). Stools also hold more water because fecal transit time is shortened. The other 40% of the bran is degraded by bacteria which stimulates bacterial growth (and bacteria make a substantial contribution to fecal mass). Many ill patients, however, cannot tolerate a high fiber diet.

Bulking agents are useful in the management of colostomy, ileostomy, hemorrhoids and anal fissure. They can help to encourage formed motions in patients with rectal discharge or bleeding. They increase fecal mass and each dose should be taken with plenty of water. They should be avoided if there is an intestinal stricture. They can take several days to produce an effect and are less useful than the stimulant or osmotic laxatives for bowel regulation.

Docusate sodium (Colace) is only a mild laxative. It is a surface wetting agent that lowers surface tension and allows water to penetrate hard feces. It also promotes secretion of fluid in both the small and large bowel. It has a weak effect on gut motility. It acts within 1 to 2 days, and should be started at the maximum dose of 500mg per day in divided doses.

Lactulose (Chronulac Syrup) is a semi-synthetic disaccharide (galactose fructose) which is not absorbed by the GI tract, and is therefore safe for diabetics. It has an osmotic effect so water and electrolytes are retained in the bowel lumen. It is estimated that 30ml of lactulose increases colonic fecal volume by about 500ml and this stimulates peristalsis in both the large and small intestine. Lactulose is metabolized by gut bacteria to acetic and lactic acids which prevent bacterial conversion of urea to ammonia and is therefore useful in hepatic encephalopathy. Lactulose 10ml to 30ml 3 times a day, plus a stimulant laxative, is usually necessary if the patient is taking opioids. It is effective within 2 days. It causes nausea in some patients. Higher doses can cause abdominal distention and gas. Tolerance may develop. The sweet taste of lactulose can be masked by mixing it with fruit juice.

Magnesium sulfate is a harsh small bowel (osmotic) flusher which also has peristaltic action, and is usually reserved for severe constipation resistant to other laxative regimes.

The author and publisher have taken precautions to ensure that the information in this book is error-free. However, readers must be guided by their own personal and professional standards of good practice in evaluating and applying recommendations made herein. The contents of this book represent the views and experience of the author, and not necessarily those of the publisher.