Medication for Irritable Bowel Syndrome

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What is Irritable Bowel Syndrome?

Irritable bowel syndrome, or IBS, is a common disorder of the large intestine. As many as one out of every five adults in the U.S. will suffer from IBS at some time in their lives. IBS causes stomach cramping, abdominal pain, gas, diarrhea, and constipation. There is a variety of medication for irritable bowel syndrome. Most cases of IBS are mild and can be managed with medication, diet and lifestyle changes.


Anticholinergics help control IBS by inhibiting nerve impulses in the smooth muscle of the bowel. They are the most commonly prescribed drugs for IBS. Common anticholinergics include hycosamine sulfate, sold under the brand name Anaspaz or Levsin. Anticholinergics work best in patients who suffer from stomach cramps with IBS. They can be taken as needed for cramps, or taken 30 to 45 minutes before meals that may worsen IBS symptoms.

Anticholinergics can make constipation worse in patients who suffer more from constipation with IBS. Side effects include drowsiness, dry mouth, nausea, blurred vision and inability to urinate. They should not be used by those who have glaucoma or urinary retention. Pregnant women should only take anticholinergics under the advice of their healthcare provider. Some studies have shown that these drugs may increase fetus heart rate and be linked to birth defects.


Antidepressants may be prescribed to IBS sufferers who have pain or depression along with IBS. Tricyclic antidepressants and selective serotonin reuptake inhibitors (SSRIs) work by inhibiting nerve activity in the bowel. If you have diarrhea and pain without depression, a low dose tricyclic antidepressant such as Tofranil may be prescribed. SSRIs such as Prozac may be prescribed for depression with pain and constipation. Side effects of antidepressants include drowsiness, dry mouth, headache, tremors, and anxiety.

Antidepressant therapy should be used cautiously in patients with seizures, severe liver or renal disease, diabetics and pregnant women. Use of supplements such as St. John’s wort and SAMe increase the risk of seratonin syndrome. This is a condition in which the body has too much seratonin. Left untreated, it can be fatal.


Lotronex is a nerve inhibitor antagonist that relaxes the colon, slowing the movement of waste through the lower bowel. It was taken off the market shortly after its initial approval because of serious complications. Lotronex may only be prescribed by doctors registered with the manufacturer. Patients must sign a statement that says they understand the risks and benefits of taking Lotronex. It is intended for IBS with severe diarrhea in women, and is not approved for use by men.

Lotronex carries the risk of serious side effects, including ischemic colitis (loss of blood flow to the bowels) and severe constipation that may rarely cause death. Your doctor should have a current list of all medications and over-the-counter supplements you take. A complete medical history, including history of blood clots, bowel blockages, Crohn’s disease, ischemic bowel disease, and other GI conditions is needed to safely prescribe Lotronex.

While taking Lotronex, call your doctor immediately if you have constipation, new or worse abdominal pain or bloody bowel movements.


Amitiza is a prescription laxative used to treat IBS with constipation in women at least 18 years of age. It works by increasing fluid in the bowel, which allows stool to pass more easily. A negative pregnancy test is required before beginning Amitiza therapy, and birth control must be used while taking it. Side effects include nausea, diarrhea, gas, tiredness and swelling of the feet, legs and hands.

Serious side effects include shortness of breath, rash, swelling of the face, lips, mouth, tongue or throat and tightness in the throat. These should be reported to your doctor immediately. Signs of overdose include fainting, pale skin, flushing, weakness and chest discomfort.


Davis’s Drug Guide for Nurses, 8th ed., 2003. F.A. Davis Co., Philadelphia.

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