Laxatives

Definition

Laxatives are products that promote bowel movements.

Purpose

Laxatives are used to treat constipation—the passage of small amounts of hard, dry stools, usually fewer than three times a week. Before recommending use of laxatives, differential diagnosis should be performed. Prolonged constipation may be evidence of a significant problem, such as localized peritonitis or diverticulitis. Complaints of constipation may be associated with obsessive-compulsive disorder. Use of laxatives should be avoided in these cases. Patients should be aware that patterns of defecation are highly variable, and may vary from two to three times daily to two to three times weekly.

Laxatives may also be used prophylacticly for patients, such as those recovering from a myocardial infarction or those who have had recent surgery, who should not strain during defecation.

Laxatives are also used to cleanse the lower bowel before a colonoscopy or similar diagnostic procedure.

Description

Laxatives may be grouped by mechanism of action.

Saline cathartics include dibasic sodium phosphate (Phospo-Soda), magnesium citrate, magnesium hydroxide (milk of magnesia), magnesium sulfate (Epsom salts), sodium biphosphate, and others. They act by attracting and holding water in the intestinal lumen, and may produce a watery stool. Magnesium sulfate is the most potent of the laxatives in this group.

Stimulant and irritant laxatives increase the peristaltic movement of the intestine. Examples include cascara and bisadocyl (Dulcolax.) Castor oil works in a similar fashion.

Bulk-producing laxatives increase the volume of the stool, and will both soften the stool and stimulate intestinal motility. Psyllium (Metamucil, Konsil) and methylcellulose (Citrucel) are examples of this type. The overall effect is similar to that of eating high-fiber foods, and this class of laxative is most suitable for regular use. Many primary care physicians suggest that patients try laxatives in this category before using saline or stimulant laxatives.

Docusate (Colace) is the only representative example of the stool softener class. It holds water within the fecal mass, providing a larger, softer stool. Docusate has no effect on acute constipation, since it must be present before the fecal mass forms to have any effect, but may be useful for prevention of constipation in patients with recurrent problems, or those who are about to take a constipating drug, such as narcotic analgesics.

Mineral oil is an emollient laxative. It acts by retarding intestinal absorption of fecal water, thereby softening the stool.

The hyperosmotic laxatives are glycerin and lactulose (Chronulac, Duphalac), both of which act by holding water within the intestine. Lactulose may also increase peristaltic action of the intestine.

Some newer options for the treatment of chronic constipation are being developed by various groups of researchers. These include such alternative therapies as biofeedback ; newer drugs like tegaserod (Zelnorm) and prucalopride, which stimulate peristalsis; a nerve growth factor known as neurotrophin-3; and electrical stimulation of the colon.

Recommended dosage

See specific products.

Precautions

Short-term use of laxatives is generally safe except in appendicitis, fecal impaction, or intestinal obstruction. Lactulose is composed of two sugar molecules; galactose and fructose, and should not be administered to patients who require a low galactose diet.

Chronic use of laxatives may result in fluid and electrolyte imbalances, steatorrhea, osteomalacia, diarrhea, cathartic colon, and liver disease. Excessive intake of mineral oil may cause impaired absorption of oil soluble vitamins, particularly A and D. Excessive use of magnesium salts may cause hypermanesemia.

Lactulose and magnesium sulfate are pregnancy category B. Casanthranol, cascara sagrada, danthron, docusate sodium, docusate calcium, docusate potassium, mineral oil and senna are category C. Casanthranol, cascara sagrada and danthron are excreted in breast milk, resulting in a potential increased incidence of diarrhea in the nursing infant.

The American College of Toxicology states that cathartics should not be used as a means of clearing poisons from the digestive tract of a poisoning victim. Although some physicians have administered these laxatives along with activated charcoal in order to reduce the body's absorption of the poison, this treatment is no longer recommended.

Interactions

Mineral oil and docusate should not be used in combination. Docusate is an emulsifying agent which will increase the absorption of mineral oil.

Bisacodyl tablets are enteric coated, and so should not be used in combination with antacids. The antacids will cause premature rupture of the enteric coating.

KEY TERMS

Carbohydrates— Compounds, such as cellulose, sugar, and starch, that contain only carbon, hydrogen, and oxygen, and are a major part of the diets of people and other animals.

Cathartic colon— A poorly functioning colon, resulting from the chronic abuse of stimulant cathartics.

Colon— The large intestine.

Diverticulitis— Inflammation of the part of the intestine known as the diverticulum.

Fiber— Carbohydrate material in food that cannot be digested.

Hyperosmotic— Hypertonic, containing a higher concentration of salts or other dissolved materials than normal tissues.

Osteomalacia— A disease of adults, characterized by softening of the bone. Similar to rickets which is seen in children.

Pregnancy category— A system of classifying drugs according to their established risks for use during pregnancy. Category A: Controlled human studies have demonstrated no fetal risk. Category B: Animal studies indicate no fetal risk, but no human studies, or adverse effects in animals, but not in well-controlled human studies. Category C: No adequate human or animal studies, or adverse fetal effects in animal studies, but no available human data. Category D: Evidence of fetal risk, but benefits outweigh risks. Category X: Evidence of fetal risk. Risks outweigh any benefits.

Steatorrhea— An excess of fat in the stool.

Stool— The solid waste that is left after food is digested. Stool forms in the intestines and passes out of the body through the anus.

Resources

BOOKS

Beers, Mark H., MD, and Robert Berkow, MD., editors. "Diarrhea and Constipation." In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

Karch, A. M. Lippincott's Nursing Drug Guide. Springhouse, PA: Lippincott Williams & Wilkins, 2003.

ORGANIZATIONS

American Society of Health-System Pharmacists (ASHP). 7272 Wisconsin Avenue, Bethesda, MD 20814. (301) 657-3000. 〈http://www.ashp.org〉.

National Digestive Diseases Information Clearinghouse. 2 Information Way, Bethesda, MD 20892-3570. nddic@aerie.com. 〈http://www.niddk.nih.gov/Brochures/NDDIC.htm〉.

United States Food and Drug Administration (FDA). 5600 Fishers Lane, Rockville, MD 20857-0001. (888) INFO-FDA. 〈http:/www.fda.gov〉.

Laxatives

Definition

A laxative is a drug that promotes bowel movements.

Purpose

Laxatives are used to prevent or treat constipation. They are also used to prepare the bowel for an examination or surgical procedure.

Description

Laxatives work in different ways, by stimulating colon movement, adding bulk to the contents of the colon, or drawing fluid or fat into the intestine. Some laxatives work by combining these functions.

Bisacodyl

Bisacodyl is a non-prescription stimulant laxative. It reduces short-term constipation and is also used to prepare the colon or rectum for an examination or surgical procedure. The drug works by stimulating colon movement (peristalsis); constipation is usually relieved within 15 minutes to one hour after administration of a suppository form and in 6 to 12 hours after taking the drug orally.

Calcium polycarbophil

Calcium polycarbophil is a non-prescription bulk-forming laxative that is used to reduce both constipation and diarrhea . It draws water to the intestine, enlarging the size of the colon and thereby stimulating movement. It reduces diarrhea by taking extra water away from the stool. This drug should relieve constipation in 12 to 24 hours and have maximum effect in three days. Colitis patients should see a reduction in diarrhea within one week.

Docusate calcium/docusate sodium

Docusate, a non-prescription laxative, helps a patient avoid constipation by softening the stool. It works by increasing the penetration of fluids into the stool by emulsifying feces, water and fat. Docusate prevents constipation and softens bowel movements and fecal impactions. This laxative should relieve constipation within one to three days.

Lactulose

Lactulose, a prescription laxative, reduces constipation and lowers blood ammonia levels. It works by drawing fluid into the intestine, raising the amount of water in the stool, and preventing the colon from absorbing ammonia. It is used to help people who suffer from chronic constipation.

Psyllium

Psyllium is a non-prescription bulk-forming laxative that reduces both constipation and diarrhea. It mixes with water to form a gel-like mass that can be easily passed through the colon. Constipation is relieved in 12 to 24 hours and maximum relief is achieved after several days.

Senna/senokot

Senna/senokot is a non-prescription laxative that reduces constipation by promoting colon movement. It is used to treat bouts of constipation and to prepare the colon for an examination or surgical procedure. This laxative reduces constipation in eight to 10 hours.

Recommended dosage

Laxatives may be taken by mouth or rectally (suppository or enema).

Bisacodyl

• Adults or children over 12 years: 5 to 15 mg taken by mouth in morning or afternoon (up to 30 mg for surgical or exam preparation).
• Adult (rectal): 10 mg.
• Children age 2 to 11 years: 10 mg rectally as single dose.
• Children over 3 years: 5 to 10 mg by mouth as single dose.
• Children under 2 years: 5 mg rectally as single dose.

Calcium polycarbophil

• Adult: 1 g by mouth every day, up to four times a day as needed (not to exceed 6 g by mouth in a 24-hour time period).
• Children age 6 to 12 years: 500 mg by mouth twice a day as needed (not to exceed 3 g in a 24-hour time period).
• Children age 3 to 6 years: 500 mg twice a day by mouth, as needed (not to exceed 1.5 g in a 24-hour time period).

Docusate

• Adult (docusate sodium): 50 to 300 mg by mouth per day.
• Adult (docusate calcium or docusate potassium): 240 mg by mouth as needed.
• Adult (docusate sodium enema): 5 ml.
• Children over 12 years (docusate sodium enema): 2 ml.
• Children age 6 to 12 years (docusate sodium): 40 to 120 mg by mouth per day.
• Children age 3 to 6 years (docusate sodium): 20 to 60 mg by mouth per day.
• Children under 3 years (docusate sodium): 10 to 40 mg by mouth every day.

Lactulose

FOR CONSTIPATION:

• Adult: 15 to 60 ml by mouth every day.
• Children: 7.5 ml by mouth every day.

FOR ENCEPHALOPATHY:

• Adult: 20 to 30 g three or four times a day until stools become soft. Retention enema: 30 to 45 ml in 100 ml of fluid.
• Infants and children: Parents should follow physician's directions for infants and children with encephalopathy.

Psyllium

• Adult: 1 to 2 teaspoons mixed in 8 ounces of water two or three times a day by mouth, followed by 8 ounces water; or one packet in 8 ounces water two or three times a day, followed by 8 ounces of water.
• Children over 6 years: 1 teaspoon mixed in 4 ounces of water at bedtime.

Senna/senokot

• Adult (Senokot): 1 to 8 tablets taken by mouth per day or 1/2 to 4 teaspoons of granules mixed in water or juice.
• Adult (rectal suppository): 1 to 2 at bedtime.
• Adult (syrup): 1 to 4 teaspoons at bedtime.
• Adult (Black Draught): 3/4 ounce dissolved in 2.5 ounces liquid given between 2 P. M. and 4 P. M. on the day prior to a medical exam or procedure.
• Children: Parents should ask their doctor as dosage is based on weight. Black Draught is not to be used by children.
• Children age 1 month to 1 year (Senokot): 1.25 to 2.5 ml of syrup at bedtime.

Precautions

The doctor should be informed of any prior allergic drug reaction, especially prior reactions to any laxatives. Pregnancy is also a concern. Animal studies have shown laxatives to have adverse effects on pregnancy, but no human studies regarding pregnancy are currently available. These drugs are only given in pregnancy after the risks to the fetus have been taken under consideration. Nursing mothers should use caution and consult their doctor before receiving these drugs.

Bisacodyl should not be administered to patients with rectal fissures, abdominal pain, nausea, vomiting, appendicitis, abdominal surgery, ulcerated hemorrhoids, acute hepatitis, fecal impaction, or blockage in the biliary tract. Calcium polycarbophil should not be given to anyone with a gastrointestinal blockage (obstruction).

Both psyllium and docusate calcium/docusate sodium should be avoided by patients with intestinal blockage, fecal impaction, or nausea and vomiting . Lactulose should be avoided by patients who are elderly, have diabetes mellitus, eat a low galactose diet, or whose general health is poor.

Finally, senna/senokot is inadvisable for patients with congestive heart failure, gastrointestinal bleeding, intestinal blockage, abdominal pain, nausea and vomiting, appendicitis, or prior abdominal surgery.

Side effects

Laxatives may have side effects. Some, such as nausea and vomiting, are more common than others. Side effects related to specific laxatives are described in this section. With repeated use, people may become dependent on laxatives. All side effects should be reported to a doctor.

Bisacodyl

Common side effects:

• nausea
• vomiting
• loss of appetite (anorexia )
• cramps

Less common side effects:

• muscle weakness
• diarrhea
• electrolyte changes
• rectal burning (when suppositories are used).

Life-threatening:

• severe muscle spasms (tetany)

Calcium polycarbophil

Side effects may include:

• abdominal bloating (distention)
• gas
• laxative dependency

Life-threatening:

• gastrointestinal obstruction

Docusate calcium/docusate sodium

Side effects include:

• bitter taste in the mouth
• irritated throat
• nausea
• cramps
• diarrhea
• loss of appetite
• rash

Lactulose

Common side effects include:

• nausea
• vomiting
• loss of appetite
• abdominal cramping
• bloating
• belching
• diarrhea

Psyllium

Common side effects include:

• nausea
• vomiting
• loss of appetite
• diarrhea

Less common side effects include:

• abdominal cramping
• blockage of the esophagus or intestine

Senna/senokot

Common side effects include:

• nausea
• vomiting
• loss of appetite
• abdominal cramping

Less common side effects include:

• diarrhea
• gas
• urine that is pink-red or brown-black in color
• abnormal electrolyte levels

Life-threatening:

• Severe muscle spasms (tetany)

Interactions

Laxatives may interact with other drugs. Sometimes, the laxative can interfere with proper absorption of another drug. A patient must notify their doctor or pharmacist if he or she is already taking any medications so that the proper laxative can be selected or prescribed. Specific drug interactions are:

• Bisacodyl: Antacids, H2-blockers, and some herbal remedies (lily of the valley, pheasant's eye, squill).
• Calcium polycarbophil: (lowers the absorption of) tetracycline.
• Docusate calcium/docusate sodium: Unknown.
• Lactulose: Neomycin and other laxatives.
• Psyllium: Cardiac glycosides, oral anticoagulants, and salicylates.
• Senna/senokot: Disulfiram should never be taken with this drug. Also, senna/senokot lowers the absorption of other drugs taken by mouth.

Rhonda Cloos, R.N.

KEY TERMS

Constipation

—Difficult or infrequent bowel movements.

Diarrhea

—Frequent, watery stools.

Electrolyte levels

—In the bloodstream, electrolyte levels are the amounts of certain acids, bases, and salts. Abnormal levels of certain electrolyes can be life-threatening.

Encephalopathy

—a brain disease.

Peristalsis

—Wave-like movement of the colon to pass feces along.

Tetany

—Muscle spasms that can be life-threatening.

Laxatives

Definition

Laxatives are products that promote bowel movements.

Description

Laxatives may be grouped by mechanism of action.

Saline cathartics include dibasic sodium phosphate (Phospo-Soda), magnesium citrate, magnesium hydroxide (milk of magnesia), magnesium sulfate (Epsom salts), sodium biphosphate, and others. They act by attracting and holding water in the intestinal lumen, and may produce a watery stool. Magnesium sulfate is the most potent of the laxatives in this group.

Stimulant and irritant laxatives increase the peristaltic movement of the intestine. Examples include cascara and bisadocyl (Dulcolax). Castor oil works in a similar fashion.

Bulk producing laxatives increase the volume of the stool, and will both soften the stool and stimulate intestinal motility. Psyillium (Metamucil, Konsil) and methylcellulose (Citrucel) are examples of this type. The overall effect is similar to that of eating high-fiber foods, and this class of laxative is most suitable for regular use.

Docusate (Colace) is the only representative example of the stool softener class. It holds water within the fecal mass, providing a larger, softer stool. Docusate has no effect on acute constipation , since it must be present before the fecal mass forms to have any effect, but may be useful for prevention of constipation in patients with recurrent problems, or those who are about to take a constipating drug, such as narcotic analgesics .

Mineral oil is an emollient laxative. It acts by retarding intestinal absorption of fecal water, thereby softening the stool.

The hyperosmotic laxatives are glycerin and lactulose (Chronulac, Duphalac), both of which act by holding water within the intestine. Lactulose may also increase peristaltic action of the intestine.

General use

Laxatives are used to treat constipation—the passage of small amounts of hard, dry stools, usually fewer than three times a week. Constipation may be caused by several conditions, some of which are potentially serious, and require medical attention:

• Neurologic—caused by failure of nerves to stimulate movement of the muscles of the intestines.
• Obstructive—failure of the muscles in the intestine to open, or presence of a mass that's blocking passage of the feces through the intestine.
• Endocrine/metabolic—caused by some diseases including hypothyroidism.
• Medicinal—caused by some drugs, including narcotic analgesics, iron, and some drugs used in cancer treatment.

Chronic constipation occurs in 1–4% of children between the ages of four and 10. If constipation continues, it should be treated by a physician.

A reasonable first step is to assure that there is enough fiber in the diet. This may be done by switching to a high fiber breakfast cereal. If this doesn't lead to improvement, then medical attention is necessary.

Precautions

Short term use of laxatives is generally safe except in appendicitis , fecal impaction, or intestinal obstruction. Lactulose is composed of two sugar molecules; galactose and fructose, and should not be administered to patients who require a low galactose diet.

Chronic use of laxatives may result in fluid and electrolyte imbalances, steatorrhea, osteomalacia, diarrhea , cathartic colon, and liver disease. Excessive intake of mineral oil may cause impaired absorption of oil solublevitamins , particularly A and D. Excessive use of magnesium salts may cause hypermanesemia.

Side effects

Excessive use of laxatives may result in dependency on these products. This may cause a condition known as cathartic colon.

Excessive use of laxatives that contain sodium or magnesium may result in dangerously high blood levels of these elements.

Interactions

Mineral oil and docusate should not be used in combination. Docusate is an emulsifying agent which will increase the absorption of mineral oil.

Bisacodyl tablets are enteric coated, and so should not be used in combination with antacids. The antacids will cause premature rupture of the enteric coating.

Preventing side effects

Used properly, laxatives are very safe. Do not overuse or give in doses larger than those labeled. If constipation persists, obtain medical help.

Parental concerns

Laxatives should not be used too frequently. Bulk laxatives such as psyllium should be the normal first choice.

Mineral oil should not be given to infants or other children while laying down. This may result in the oil going into the lungs.

KEY TERMS

Carbohydrates —Compounds, such as cellulose, sugar, and starch, that contain only carbon, hydrogen, and oxygen, and are a major part of the diets of people and other animals.

Cathartic colon —A poorly functioning colon, resulting from the chronic abuse of stimulant cathartics.

Colon —The part of the large intestine that extends from the cecum to the rectum. The sigmoid colon is the area of the intestine just above the rectum; linking the descending colon with the rectum. It is shaped like the letter S.

Diverticulitis —Inflammation of the diverticula (small outpouchings) along the wall of the colon, the large intestine.

Fiber —Carbohydrate material in food that cannot be digested.

Hyperosmotic —Hypertonic, containing a higher concentration of salts or other dissolved materials than normal tissues.

Osteomalacia —A bone disease that occurs in adults due to a prolonged period of vitamin D deficiency. It is characterized by softening of the bone and is sometimes referred to as adult rickets.

Steatorrhea —An excessive amount of fat in the feces due to poor fat absorption in the gastrointestinal tract.

Stool —The solid waste that is left after food is digested. Stool forms in the intestines and passes out of the body through the anus.

Resources

BOOKS

Beers, Mark H. and Robert Berkow, eds. The Merck Manual of Diagnosis and Therapy, 17th ed. Whitehouse Station, NJ: Merck and Company, Inc., 1999.

McAvoy, G., Miller J., Litvak K. AHFS Drug Information 2004. Amer. Soc Healthsys. Pharm, Bethesda 2004.

Siberry G.K., Iannone R. The Harriet Lane Handbook 15th ed. Mosby Publishing, Philadelphia, 2000.

PERIODICALS

Bell, EA, Wall, GC. "Pediatric constipation therapy using guidelines and polyethylene glycol 3350." Ann Pharmacother. 2004 Apr;38(4):686-93.

"Constipation, Laxatives and Dietary Fiber." HealthTips (April 1993): 9.

Griffin, GC, Roberts, SD, Graham, G. "How to resolve stool retention in a child. Underwear soiling is not a behavior problem." Postgrad Med 1999 Jan;105(1):159-61, 165-6, 172-3.

"Overuse Hazardous: Laxatives Rarely Needed." (Includes related article on types of laxatives.) FDA Consumer (April 1991): 33.

Patel, H, Law, A, Gouin, S. "Predictive factors for short-term symptom persistence in children after emergency department evaluation for constipation." Arch Pediatr Adolesc Med. 2000 Dec;154(12):1204-8.

ORGANIZATIONS

American Academy of Family Physicians 11400 Tomahawk Creek Parkway Leawood, KS 66211-2672.

WEB SITES

Constipation in Infants and Children: Evaluation and Treatment. American Academy of Pediatrics. <http://www.aap.org/policy/constipation.htm> (accessed February 15, 2005).

Section on Gastroenterology and Nutrition (SOGN). American Academy of Pediatrics. <http://www.aap.org/sections/gstrnut.htm> (accessed February 15, 2005).

Samuel Uretsky, PharmD

Laxatives

Definition
Purpose
Description
Precautions
Interactions
Recommended dosage

Definition

Laxatives are medicines that promote bowel movements.

Purpose

Laxatives are used to treat constipation—the passage of small amounts of hard, dry stools, usually fewer than three times a week. Before recommending the use of laxatives, a physician should perform differential diagnosis. Prolonged constipation may be evidence of a significant problem, such as localized peritonitis or diverticulitis. Complaints of constipation may be associated with obsessive-compulsive disorder. Use of laxatives should be avoided in these cases. Patients should be aware that patterns of defecation are highly variable, and may vary from two to three times daily to two to three times weekly.

Laxatives may also be used prophylacticly for patients such as those recovering from a myocardial infarction (heart attack) or those who have had recent surgery and should not strain during defecation.

Description

Laxatives may be grouped by mechanism of action.

Saline cathartics include dibasic sodium phosphate (Phospo-Soda), magnesium citrate, magnesium hydroxide (milk of magnesia), magnesium sulfate (Epsom salts), sodium biphosphate, and others. They act by attracting and holding water in the intestinal tissues, and may produce a watery stool. Magnesium sulfate is the most potent of the laxatives in this group.

Stimulant and irritant laxatives increase the peristaltic movement of the intestine. Product examples include cascara and bisadocyl (Dulcolax). Castor oil works in a similar fashion.

Bulk-producing laxatives increase the volume of the stool, and will both soften the stool and stimulate intestinal motility. Psyllium (Metamucil, Konsil) and methylcellulose (Citrucel) are examples of this type. The overall effect is similar to that of eating high-fiber foods, and this class of laxative is most suitable for regular use.

Docusate (Colace) is the only representative example of the stool softener class. It holds water within the fecal mass, providing a larger, softer stool. Docusate has no effect on acute constipation, since it must be present before the fecal mass forms to have any effect, but may be useful for prevention of constipation in patients with recurrent problems, or those who are about to take a constipating drug such as narcotic analgesics .

Mineral oil is an emollient laxative. It acts by retarding intestinal absorption of fecal water, thereby softening the stool.

The hyperosmotic laxatives are glycerin and lac-tulose (Chronulac, Duphalac), both of which act by holding water within the intestine. Lactulose may also increase peristaltic action of the intestine.

Precautions

Short-term use of laxatives is generally safe except in cases of appendicitis, fecal impaction, or intestinal obstruction. Lactulose is composed of two sugar molecules, galactose and fructose, and should not be administered to patients who require a low-galactose diet.

KEY TERMS

Carbohydrates— Compounds such as cellulose, sugar, and starch that contain only carbon, hydrogen, and oxygen, and are a major part of the diets of people and other animals.

Cathartic colon— A poorly functioning colon, resulting from the chronic abuse of stimulant cathartics.

Colon— The large intestine.

Diverticulitis— Inflammation of the part of the intestine known as the diverticulum.

Fiber— Carbohydrate material in food that cannot be digested.

Hyperosmetic— Hypertonic, containing a higher concentration of salts or other dissolved materials than normal tissues.

Osteomalacia— A disease of adults, characterized by softening of the bone; similar to rickets, which is seen in children.

Pregnancy category— A system of classifying drugs according to their established risks for use during pregnancy: category A: controlled human studies have demonstrated no fetal risk; category B: animal studies indicate no fetal risk, and there are no adequate and well-controlled studies in pregnant women; category C: no adequate human or animal studies, or adverse fetal effects in animal studies, but no available human data; category D: evidence of fetal risk, but benefits outweigh risks; category X: evidence of fetal risk, which outweigh any benefits.

Steatorrhea— An excess of fat in the stool.

Stool— The solid waste that is left after food is digested. Stool forms in the intestines and passes out of the body through the anus.

Chronic use of laxatives may result in fluid and electrolyte imbalances, steatorrhea, osteomalacia, diarrhea, cathartic colon, and liver disease. Excessive intake of mineral oil may cause impaired absorption of oil soluble vitamins, particularly A and D. Excessive use of magnesium salts may cause hypermanesemia.

Lactulose and magnesium sulfate are pregnancy category B. Casanthranol, cascara sagrada, danthron, docusate sodium, docusate calcium, docusate potassium, mineral oil, and senna are category C. Casanthranol, cascara sagrada, and danthron are excreted in breast milk, resulting in a potential increased incidence of diarrhea in the nursing infant.

Interactions

Mineral oil and docusate should not be used in combination. Docusate is an emulsifying agent that will increase the absorption of mineral oil.

Bisacodyl tablets are enteric coated, and so should not be used in combination with antacids. The antacids will cause premature rupture of the enteric coating.

Recommended dosage

The patient should consult specialized drug references, or ask a physician or pharmacist about a specific medication.

Resources

PERIODICALS

“Constipation, Laxatives and Dietary Fiber.” HealthTips (April 1993): 9.

“Overuse Hazardous: Laxatives Rarely Needed.” FDA Consumer (April 1991): 33.

ORGANIZATIONS

National Digestive Diseases Information Clearinghouse. 2 Information Way, Bethesda, MD 20892-3570. <nddic@aerie.com>. http://www.niddk.nih.gov/Brochures/NDDIC.htm.

OTHER

“Effectiveness of Laxatives in Adults.” Centre for Reviews and Dissemination, University of York. [cited June 2003] http://www.york.ac.uk/inst/crd/ehc71.htm.

“Laxatives (Oral).” Medline Plus Drug Information. [cited June 2003] http://www.nlm.nih.gov/medlineplus/druginfo/uspdi/202319.html.

Samuel D. Uretsky, PharmD

Laxatives

Definition

Laxatives are products that promote bowel movements.

Purpose

Laxatives are used to treat constipation—the passage of small amounts of hard, dry stools, usually fewer than three times a week. Before recommending use of laxatives, differential diagnosis should be performed. Prolonged constipation may be evidence of a significant problem, such as localized peritonitis or diverticulitis . Complaints of constipation may be associated with obsessive-compulsive disorder. Use of laxatives should be avoided in these cases. Patients should be aware that patterns of defecation are highly variable, and may vary from two to three times daily to two to three times weekly.

Laxatives may also be used prophylacticly for patients, such as those recovering from a myocardial infarction or those who have had recent surgery, who should not strain during defecation.

Laxatives are also used to cleanse the lower bowel before a colonoscopy or similar diagnostic procedure.

Description

Laxatives maybe grouped by mechanism of action.

Saline cathartics include dibasic sodium phosphate (Phospo-Soda), magnesium citrate, magnesium hydroxide (milk of magnesia), magnesiumsulfate (Epsom salts), sodium biphosphate, and others. They act by attracting and holding water in the intestinal lumen, and may produce a watery stool. Magnesium sulfate is the most potent of the laxatives in this group.

Stimulant and irritant laxatives increase the peristaltic movement of the intestine. Examples include cascara and bisadocyl (Dulcolax.) Castor oil works in a similar fashion.

Bulk-producing laxatives increase the volume of the stool, and will both soften the stool and stimulate intestinal motility. Psyllium (Metamucil, Konsil) and methylcellulose (Citrucel) are examples of this type.

The overall effect is similar to that of eating high-fiber foods, and this class of laxative is most suitable for regular use. Many primary care physicians suggest that patients try laxatives in this category before using saline or stimulant laxatives.

Docusate (Colace) is the only representative example of the stool softener class. It holds water within the fecalmass, providing a larger, softer stool. Docusate has no effect on acute constipation, since it must be present before the fecal mass forms to have any effect, but may be useful for prevention of constipation in patients with recurrent problems, or those who are about to take a constipating drug, such as narcotic analgesics.

Mineral oil is an emollient laxative. It acts by retarding intestinal absorption of fecal water, thereby softening the stool.

The hyperosmotic laxatives are glycerin and lactulose (Chronulac, Duphalac), both of which act by holding water within the intestine. Lactulose may also increase peristaltic action of the intestine.

Some newer options for the treatment of chronic constipation are being developed by various groups of researchers. These include such alternative therapies as biofeedback ; newer drugs like tegaserod (Zelnorm) and prucalopride, which stimulate peristalsis; a nerve growth factor known as neurotrophin-3; and electrical stimulation of the colon.

Recommended dosage

See specific products.

Precautions

Short-term use of laxatives is generally safe except in appendicitis, fecal impaction, or intestinal obstruction. Lactulose is composed of two sugar molecules; galactose and fructose, and should not be administered to patients who require a low galactose diet .

KEY TERMS

Cathartic colon —Apoorly functioning colon, resulting from the chronic abuse of stimulant cathartics.

Colon —The large intestine.

Fiber —Carbohydrate material in food that cannot be digested.

Hyperosmotic —Hypertonic, containing a higher concentration of salts or other dissolved materials than normal tissues.

Osteomalacia —A disease of adults, characterized by softening of the bone. Similar to rickets which is seen in children.

Steatorrhea —An excess of fat in the stool.

Stool —The solid waste that is left after food is digested. Stool forms in the intestines and passes out of the body through the anus.

Chronic use of laxatives may result in fluid and electrolyte imbalances, steatorrhea, osteomalacia, diarrhea , cathartic colon, and liver disease. Excessive intake of mineral oil may cause impaired absorption of oil soluble vitamins , particularly A and D. Excessive use of magnesium salts may cause hypermanesemia.

The American College of Toxicology states that cathartics should not be used as a means of clearing poisons from the digestive tract of a poisoning victim.

Although some physicians have administered these laxatives along with activated charcoal in order to reduce the body's absorption of the poison, this treatment is no longer recommended.

Interactions

Mineral oil and docusate should not be used in combination. Docusate is an emulsifying agent which will increase the absorption of mineral oil.

Bisacodyl tablets are enteric coated, and so should not be used in combination with antacids . The antacids will cause premature rupture of the enteric coating.

Resources

BOOKS

Beers, Mark H., MD, and Robert Berkow, MD., editors. “Diarrhea and Constipation.” In The Merck Manual of

Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

Karch, A. M. Lippincott's Nursing Drug Guide. Springhouse, PA: Lippincott Williams & Wilkins, 2003.

ORGANIZATIONS

American Society of Health-System Pharmacists (ASHP). 7272 Wisconsin Avenue, Bethesda, MD 20814. (301) 657-3000. http://www.ashp.org.

National Digestive Diseases Information Clearinghouse. 2 Information Way, Bethesda, MD 20892-3570. nddic@aerie.com. http://www.niddk.nih.gov/Brochures/NDDIC.htm.

United States Food and Drug Administration (FDA). 5600 Fishers Lane, Rockville, MD 20857-0001. (888) INFO-FDA. http:/www.fda.gov.

Samuel D. Uretsky PharmD

Rebecca J. Frey Ph.D.