Laxatives For Constipation (cont.)

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Saline laxatives and osmotic laxatives

The active ingredients in saline laxatives are mostly magnesium, sulfate, citrate, and phosphate ions. These ions draw water into the intestines. The additional water softens the stool, increases pressure within the intestines, and increases intestinal contractions resulting in the discharge of softer stool. Fleet Phospho-Soda, milk of magnesia, and magnesium citrate are examples of saline laxatives.

Oral doses of saline laxatives should be taken with one to two 8 ounce glasses of water. The onset of bowel response is usually 1/2 to 3 hours after consuming the laxative. Small doses are sometimes recommended for the treatment of occasional constipation, while larger doses can produce complete evacuation of the intestine. Complete cleansing of the bowel is useful in preparing for colonoscopy, sigmoidoscopy, and barium enema.

The active ingredient in osmotic-type laxatives such as GoLYTELY, GlycoLax, and MiraLax is polyethylene glycol (PEG). These work by holding water in the stool to soften the stool and increasing the number of bowel movements. Osmotic-type laxatives are often used to cleanse the bowel prior to colonoscopies or colon surgery.

Precautions about using saline and osmotic laxatives

Since there may be some absorption of the active ingredients from the intestines into the blood circulation, saline laxatives should not be used in certain individuals. Individuals with impaired kidney function should not use laxatives containing magnesium or phosphate salts. Excess accumulation of magnesium and phosphate in the blood of these individuals can lead to toxicity. Those who need to limit their sodium intake, such as those with congestive heart failure, kidney disease, and high blood pressure, should not use laxatives that contain sodium.

Side effects of osmotic-type laxatives include nausea, abdominal cramping, or gas. People who have a history of abdominal surgery or bowel obstruction should consult their doctor before using this medication. Caution is advised when using this drug in the elderly because they may be more sensitive to its side effects, especially diarrhea.

Medically Reviewed by a Doctor on 4/22/2014

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