Merck Manual

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Agents Used to Prevent or Treat Constipation

Agents Used to Prevent or Treat Constipation

Agent

Some Side Effects

Comments

Bulking agents (fiber)*

Bran

Bloating, passing of gas (flatulence), and poor absorption of iron and calcium

Bulking agents generally are used to prevent or control chronic constipation.

Polycarbophil

Bloating and flatulence

Methylcellulose

Less bloating than with other fiber agents

Psyllium

Bloating and flatulence

Stool softeners

Docusate

Stool softeners may be used to treat constipation and are often used to help prevent it.

Docusate is not effective for severe constipation.

Glycerin

Rectal irritation

Mineral oil

Lung inflammation caused by fats in the lungs (lipid pneumonia), poor absorption of fat-soluble vitamins, dehydration, and loss of control over bowel movements (fecal incontinence)

Osmotic agents

Lactulose

Abdominal cramps and flatulence

Osmotic agents are better for treating constipation than for preventing it.

Magnesium salts (magnesium hydroxide and magnesium citrate)

Too much magnesium in the body (magnesium toxicity), dehydration, abdominal cramps, and fecal incontinence

Polyethylene glycol

Fecal incontinence (related to dosage)

Sodium phosphate

Rare cases of sudden kidney failure

Sorbitol

Abdominal cramps and flatulence

Stimulant laxatives

Anthraquinones (found in senna, cascara, and castor oil)

Abdominal cramps and dehydration

Stimulant laxatives are not used if there is a possibility of an intestinal obstruction.

Prolonged use can damage the large intestine.

Lubiprostone can be used for chronic constipation. It is available for long-term use.

Bisacodyl

Fecal incontinence, a low level of potassium in the blood (hypokalemia), abdominal cramps, and rectal burning with daily use of the suppository form

Linaclotide

Abdominal cramps, flatulence

Not used in children

Lubiprostone

Nausea, particularly when the drug is taken on an empty stomach, and headache

Plecanatide†

Dizziness, urinary tract infection (not common)

Prucalopride†

Headache, abdominal pain

Enemas

Mineral oil or olive oil retention

Fecal incontinence

Although rare, giving an enema can injure the rectum if the procedure is done roughly.

Tap water

Fluid overload if a lot of water is absorbed

Phosphate

A high level of phosphate in the blood (hyperphosphatemia)

Soapsuds

Cramps

* The dose of fiber supplements should be gradually increased over several weeks to the recommended dose.

† These drugs are available only by prescription.