According to the National Digestive Disease Information Center, NDDIC, more than 4 million Americans experience constipation yearly. People over age 65; post-surgical, post-stroke and palliative-care patients; and pregnant women who suffer from constipation. Their remedy of choice: over-the-counter colon cleaners or laxatives. High-fiber foods, herbs and other substances have been used to induce bowel movement, but laxatives are the preferred purgative.
Classified according to their mode of action, laxatives serve as bulk-forming agents, osmotic laxatives, stimulant purgatives, lubricating agents, saline laxatives and chloride charcoal activators.
Bulk-Forming Agents
Bulking compounds such as bran, psyllium, calcium polycarbophil and methylcellulose -- along with sufficient liquid -- adds bulk to the stool. This stimulates contraction of the bowels, prompting defecation. Slow-acting, but considered the safest of the drug laxatives, bulk-forming substances initially should be taken in small amounts. After bowel regularity is established, the dose can be increased. Avoid dehydrating fluids such as alcohol and beverages that contain caffeine.
Stimulant Laxatives
Purgatives that excite the walls of the large intestine, causing it to contract and move the stool, are called stimulant laxatives. Senna, cascara, bisacodyl, castor oil and phenolphtalein work within 15 minutes to one hour of administration. Because they cause cramping, irritation of the bowels, dependency and potential risk for colon cancer, prolonged use of stimulant laxatives is discouraged. They are used before diagnostic procedures, and prevent constipation caused by other drugs like narcotics.
Osmotic Laxatives
Osmotic agents draw large amounts of fluids into the colon, distending and stimulating its walls, triggering contractions. The excess water softens the stool, making it easier to pass. Osmotic agents contain either salts or poorly absorbed sugar such as sorbitol. Some osmotic agents containing sodium or magnesium phosphate can cause electrolyte imbalance since they are partially absorbed in the bloodstream. Because of this effect, osmotic laxatives may be harmful to persons with kidney disorders or diabetes, as well as young children and babies.
They work within 3 hours, and are better at treating rather than preventing constipation. They are useful before diagnostic procedures and for persons with idiopathic, or constipation of unknown, origin.
Stool Softeners
Water-absorbent laxatives increase the amount of water the stools can hold, softening them and making them easier to eliminate. They are the preferred laxative for women after giving birth or surgery because they minimize straining. However, just like osmotic laxatives, prolonged use of stool softeners is discouraged as they may cause electrolyte imbalance.
Lubricants
Mineral oil is perhaps the best known example of a lubricant-purgative. The oil coats the stool which helps it move along the large intestines. However, it is contraindicated for pregnant women since it can decrease the absorption of fat-soluble vitamins. During pregnancy, a woman's requirement for all nutrients increases due to the increased demands of the growing fetus; using mineral oil therefore at this time is inappropriate. In general, mineral oil works within eight hours.
Saline Laxatives and Chloride Channel Activators
Like osmotic laxatives and stool softeners, saline agents draw water into the large intestines. They relieve acute constipation in cases where there is no bowel obstruction. Because they can cause electrolyte imbalance, their use by persons with kidney disorders and small children should be avoided.
Chloride channel activators pull fluids into the bowels and increase contractions, which helps propel the stool along the large intestines and out of the body.
Best Strategies Against Constipation
Using laxatives judiciously and on a short-term basis has been found to be an effective remedy for constipation. However, the safest and most natural remedy is to consume a fiber-rich diet, to drink plenty of fluids such as water, fruit and vegetable juices and milk, avoid or limit alcohol intake and consumption of caffeine-containing beverages as they tend to dehydrate rather than hydrate, be physically active and respond to the urge to defecate.
References
- Pubmed:The uses and abuses of laxatives
- Pubmed: Constipation-modern laxative therapy
- Pubmed: The status of vitamin B6, B12, folate, and of homocysteine in geriatric home residents receiving laxatives or dietary fiber
- Pubmed: Constipation-modern laxative therapy
- Pubmed: Drugs producing vitamin deficiencies
- Stroke: New-Onset Constipation and Acute Stage After First Stroke
