Laxatives For Constipation (cont.)

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

• 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.

Source: MedicineNet.com
http://www.medicinenet.com/laxatives_for_constipation/article.htm