Saline laxatives are soluble inorganic salts that contain multivalent cations or anions (milk of magnesia, magnesium citrate, and sodium phosphate [Fleet Phospho Soda]).These charged particles do not readily cross the intestinal mucosa and therefore tend to remain in the lumen of the GI tract, where they help retain fluid through the osmotic effect exerted by the unabsorbed ions. The volume in the GI tract is increased, distending the colon and producing a physiological stimulus for peristalsis through activation of stretch receptors. This explanation of the mechanism by which the saline laxatives exert their effects, however, may be too simplistic, since active secretion of fluid into the gut lumen has been documented following the administration of magnesium-containing agents.
These salts should always be given with substantial amounts of water; otherwise the patient may be purged at the expense of body water, resulting in dehydration. Sodium-containing laxatives should not be used in patients with congestive heart failure, since the patient may absorb excessive sodium. Similarly, in cases of renal failure, magnesium or phosphate-containing products should not be used, since the loss of a renal clearance of these ions may result in cumulative toxic levels despite their minimal absorption.
Enemas may contain water, salts, soap, mineral detergent (docusate potassium), or hypertonic (sorbitol, sodium phosphate-biphosphate) fluids. These are convenient and generally safe for short-term use. Many of these solutions irritate the mucosa and may produce excessive mucus in the stool. Excessive use of these enema products may result in water intoxication and hypona-tremia.
A new formulation of a saline laxative, Visicol, that is useful to prepare patients for procedures, was approved for use in 2001. Each 2-g tablet contains 1.102 g sodium phosphate monobasic monohydrate and 0.398 g sodium phosphate dibasic anhydrous, for a total of 1.5 g sodium phosphate. Visicol tablets, taken in two doses of 30 g approximately 12 hours apart, induce diarrhea that rapidly and effectively cleanses the entire colon. Each administration has a purgative effect for approximately 1 to 3 hours.
Was this article helpful?
Did you ever think feeling angry and irritable could be a symptom of constipation? A horrible fullness and pressing sharp pains against the bladders can’t help but affect your mood. Sometimes you just want everyone to leave you alone and sleep to escape the pain. It is virtually impossible to be constipated and keep a sunny disposition. Follow the steps in this guide to alleviate constipation and lead a happier healthy life.