Laxatives For Constipation (cont.)

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Lubricant laxatives

Mineral oil (liquid petrolatum) coats and softens stool. Like stool softeners, mineral oil is used by patients who need to avoid straining (for example, after hernia repair, hemorrhoid surgery, heart attacks, and childbirth).

Precautions for using lubricant laxatives

  • Mineral oil should be avoided in individuals taking blood thinners, such as warfarin (Coumadin). Mineral oil decreases the absorption of vitamin K (important in forming clotting factors in the blood) from the intestines. The decreased absorption of vitamin K in patients taking warfarin can potentially lead to "over-thinning" of the blood and increasing the risk of excessive bleeding.
  • Mineral oil should not be taken during pregnancy since it may inhibit vitamin absorption and decrease the availability of vitamin K to the fetus.
  • Mineral oil can cause pneumonia if it leaks into the lungs. Leakage of secretions and other contents from the mouth and the esophagus into the lungs is called aspiration. Certain individuals (for example, the very young, the elderly, stroke victims, and those with swallowing difficulties) are prone to aspirate, especially while lying down. Therefore, mineral oil should not be given at bedtime or to individuals who are prone to aspirate.
  • Mineral oil should only be used for short periods of time. A significant absorption of mineral oil into the body can occur if used repeatedly over prolonged periods.

Stimulant laxatives

Stimulant laxatives induce bowel movements by increasing the contraction of muscles in the intestines, and are effective when used on a short-term basis. Examples of stimulant laxatives include aloe, cascara, senna compounds, bisacodyl, and castor oil. Bisacodyl (Dulcolax, Correctol) is available OTC in oral pill form and as a suppository or enema. The oral form takes 6 to 10 hours to work. Bisacodyl is commonly used in cleansing the colon for colonoscopies, barium enemas, and intestinal surgeries. While effective for occasional constipation, bisacodyl should not be taken for more than a week, and a doctor should supervise repeated use.

Other stimulant laxatives include senna (Ex-Lax, Senokot), cascara sagrada (Nature's Remedy), and casanthranol. These laxatives are converted by the bacteria in the colon into active compounds, which then stimulate the contraction of colon muscles. After taking these products orally, bowel movements occur after 8 to 24 hours. Prolonged, chronic use of these laxatives can cause the lining of the colon to become darker than normal (melanosis coli) due to the accumulation of a pigment (melanin).

Castor oil (an ingredient of Purge Concentrate) is a liquid stimulant laxative that works in the small intestine. It causes the accumulation of fluid in the small intestine and promotes evacuation of the bowels. Castor oil should not be taken with food, although juice or other flavored liquids can help hide its unpleasant taste. This laxative works rather quickly, usually within 2 to 6 hours. Castor oil is usually used to cleanse the colon for surgery, barium enema, or colonoscopy. The absorption of nutrients and minerals by the small intestine can be impaired by the frequent use of castor oil. This medicine is not recommended for the repeated treatment for constipation.

Precautions for using stimulant laxatives

  • The intensity of the action of stimulant laxatives is dose related. A large dose of any stimulant laxative can produce serious adverse effects.
  • Side effects include severe cramps, excess fluid loss and dehydration, blood electrolyte disturbances such as low levels of blood potassium (hypokalemia), and malnutrition with chronic use.
  • There is concern that chronic, long-term use of stimulant laxatives can lead to loss of colon function (cathartic colon). After years to decades of frequent use of stimulant laxatives, the nerves of the colon slowly disappear, the colon muscles wither, and the colon becomes dilated. Consequently, constipation may become increasingly worse and unresponsive to laxatives. It is not clear, however, which comes first; a progressive decrease in colon function that leads to the use of stimulant laxatives, or the use of laxatives that leads to a decrease in colon function. Nevertheless, long term use of stimulant laxatives usually is reserved for use after other treatments have failed.
Medically Reviewed by a Doctor on 4/22/2014

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