William C. Shiel Jr., MD, FACP, FACR
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
In this Article
- Constipation facts
- What is constipation?
- What causes constipation?
- Medications that cause constipation
- Other causes of constipation
- What are constipation symptoms?
- How is constipation diagnosed (evaluated)?
- Exams and tests
- Imaging studies and other tests
- What treatments are available for constipation?
- Dietary fiber and bulk-forming laxatives to treat constipation
- Other laxatives to treat constipation
- Other laxatives and OTC products to treat constipation
- Prescription drugs to treat constipation
- Other treatments for constipation
- What is the approach to the evaluation and treatment of constipation?
- When should I seek medical care for chronic constipation?
- What is new in the treatment of constipation?
- Pictures of Constipation Myths and Facts - Slideshow
- Pictures of Irritable Bowel Syndrome (IBS) - Slideshow
- Pictures of What's Causing Your Pelvic Pain - Slideshow
Other laxatives and OTC products to treat constipation
Saline laxatives contain non-absorbable ions such as magnesium, sulfate, phosphate, and citrate [for example, magnesium citrate (Citroma), magnesium hydroxide, sodium phosphate). These ions remain in the colon and cause water to be drawn into the colon. Again, the effect is softening of the stool.
Magnesium also may have mild stimulatory effects on the colonic muscles. The magnesium in magnesium-containing laxatives is partially absorbed from the intestine and into the body. Magnesium is eliminated from the body by the kidneys. Therefore, individuals with impaired kidney function may develop toxic levels of magnesium from chronic (long duration) use of magnesium-containing laxatives.
Saline laxatives act within a few hours. In general, potent saline laxatives should not be used on a regular basis. If major diarrhea develops with the use of saline laxatives and the lost fluid is not replaced by the consumption of liquids, dehydration may result. For constipation, the most frequently-used and mildest of the saline laxatives is milk of magnesia. Epsom Salt is a more potent saline laxative that contains magnesium sulfate.
Learn more about: magnesium sulfate
Stimulant laxatives cause the muscles of the small intestine and colon to propel their contents more rapidly. They also increase the amount of water in the stool, either by reducing the absorption of the water in the colon or by causing active secretion of water in the small intestine.
The most commonly-used stimulant laxatives contain cascara (castor oil), senna (for example, Ex-Lax, Senokot), and aloe. Stimulant laxatives are very effective, but they can cause severe diarrhea with resulting dehydration and loss of electrolytes (especially potassium). They also are more likely than other types of laxatives to cause intestinal cramping. There is concern that chronic use of stimulant laxatives may damage the colon and worsen constipation, as previously discussed. Bisacodyl (for example, Dulcolax, Correctol) is a stimulant laxative that affects the nerves of the colon which, in turn, stimulate the muscles of the colon to propel its contents. Prunes also contain a mild colonic stimulant.
There are many different types of enemas. By distending the rectum, all enemas (even the simplest type, the tap water enema) stimulate the colon to contract and eliminate stool. Other types of enemas have additional mechanisms of action. For example, saline enemas cause water to be drawn into the colon. Phosphate enemas (for example, Fleet phosphosoda) stimulate the muscles of the colon. Mineral oil enemas lubricate and soften hard stool. Emollient enemas (for example, Colace, Microenema) contain agents that soften the stool.
Enemas are particularly useful when there is impaction, which is hardening of stool in the rectum. In order to be effective, the instructions that come with the enema must be followed. This requires full application of the enema, appropriate positioning after the enema is instilled, and retention of the enema until cramps are felt. Defecation usually occurs between a few minutes and one hour after the enema is inserted.
Enemas are meant for occasional rather than regular use. The frequent use of enemas can cause disturbances of fluids and electrolytes in the body. This is especially true of tap water enemas. Soapsuds enemas are not recommended because they can seriously damage the rectum.
As is the case with enemas, different types of suppositories have different mechanisms of action. There are stimulant suppositories containing bisacodyl (for example, Dulcolax). Glycerin suppositories are believed to have their effect by irritating the rectum. The insertion of the finger into the rectum when the suppository is placed may itself stimulate a bowel movement.
There are many products that combine different laxatives. For example, there are oral products that combine senna and psyllium (Perdiem), senna and docusate (Senokot-S), and senna and glycerin (Fletcher's Castoria). One product even combines three laxatives, senna-like casanthranol, docusate, and glycerin (Sof-lax Overnight). These products may be convenient and effective, but they also contain stimulant laxatives. Therefore, there is concern about permanent colonic damage with the use of these products, and they probably should not be used for long-term treatment unless non-stimulant treatment fails.
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