Constipation and Laxatives

Constipation continues to be a problem for up to 30 percent of the population.

This is not something new. Even during the time of Hippocrates, people were worried about their bowel movements. It was recognized then that eating unrefined foods gave better bowel movements and better health.

Dictionary defines constipation as difficult, incomplete, or infrequent evacuation of dry hardened feces from the bowels. For some it means straining to have a bowel movement, to others a process of passing hard stools, or infrequent passage of stools, or inability to defecate at will.

A study of healthy people in Great Britain found that 99 percent of the population had between three bowel movements a week and three bowel movements a day.

Constipation is associated with (not necessarily caused by) inactivity, low calorie intake, number of medications being taken, low income, and a low education level. Constipation is also associated with depression as well as physical and sexual abuse, says an article in Gastroenterology.

Constipation can be due to slow transit of low quantity of stool which fails to stimulate the colon to move in orderly fashion. There may also be uncoordinated movement of the colon near the rectum or dysfunctional pelvic floor which causes pseudo-obstruction.

The Gastroenterology article says that about 60 percent of patients with constipation have irritable bowel syndrome with normal colonic transit time (or slightly delayed only). About 30 percent have pelvic floor dysfunction (with or without slow transit), and 10 percent has slow transit only.

Management of constipation starts with history and physical examination, review of patient’s current medications, basic blood work and investigation of the colon to rule out bowel blockage.

If everything is normal then constipation may be easily corrected by increasing dietary fiber (bran, cereal, fresh fruit, and vegetables), intake of liquids and increasing physical activity.

If this fails then use of laxatives (agents which promote evacuation of the bowel) become necessary. Commonly used laxatives are described here briefly.

Bulk forming agents (psyllium, methylcellulose) are considered the safest. They work like a sponge – they soften stool by holding water in the fecal matter.

Stool softeners (docussate sodium) soften faces by lowering the surface tension of fluids in the bowel which seems to allow more water to remain in the stool.

Stimulants (senna, bisacodyl, cascara, castor oil) act by increasing the colonic muscle contractions. Long term use of these agents is discouraged because of the theoretical risk of damaging the nerve centers in the colon.

Lubricants like mineral oil (liquid paraffin) is chemically inert and not digested in the gut. It probably acts by lubricating the bowel. It may interfere with absorption of fat soluble vitamins such as A, D and K. Sometimes aspiration of liquid paraffin may cause pneumonia.

Lactulose is a synthetic disaccharide. It is not absorbed in the gut. Its mode of action as a laxative is not clear.

Magnesium and phosphate containing agents are considered saline laxatives. They work by drawing water into the large bowel. They should be used with care in patients with kidney and heart problems.

This is only a short list of common laxatives. There are numerous other off the counter laxatives which are used and abused by the general public. For most patients proper use of laxatives is all that is required. For a small minority, our options should go beyond laxatives and include behavioral treatment as well as new drugs.

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