Lotronex is a prescription medication for women with severe irritable bowel syndrome with diarrhea (IBS-D). Lotronex may help female patients who have severe diarrhea from IBS, who have been experiencing IBS-D for six months or longer, and who have not gotten relief from any other medications they have tried.1

Lotronex is a serotonin-3 receptor antagonist. Serotonin is a chemical in the body that is involved in the messages of pain perception, the sleep-wake cycle and mood. Ninety-five percent of all the serotonin in the human body is found in the gut. As an antagonist, Lotronex blocks the receptor sites where serotonin usually binds. It is believed that too much serotonin in the gut may cause bowel movements to occur too quickly, leading to bowel urgency and diarrhea, as well as more sensitivity to pain and discomfort in the abdomen. Blocking the serotonin from binding to the receptors may help reduce some of the symptoms of severe IBS with diarrhea.1

Taking Lotronex

Lotronex works by reducing effects of having too much serotonin in the intestines. It is recommended that patients who are prescribed Lotronex take it every day – not just when symptoms flare. Patients are advised to take Lotronex twice a day. If a dose is missed, patients should skip that dose and continue with the next dose. It is not advisable to take two doses at the same time.1

Lotronex comes in two strengths: 0.5 mg and 1.0 mg capsules. Patients are usually started on the lower dose to evaluate how Lotronex works for them. Doctors may increase the dose after four weeks to the 1.0 mg capsule twice a day.1

Who Shouldn’t Take Lotronex

There has not been enough data to support if Lotronex is safe and effective for men or for children under the age of 18. In addition, Lotronex should not be used by patients with IBS with constipation (IBS-C) or by patients who are currently experiencing constipation. Patients who have experienced bowel blockages, blood clots, Crohn’s disease, ulcerative colitis, diverticulitis, severe liver disease, or who are taking a medication called Luvox® (fluvoxamine) should not take Lotronex.1

There are no studies that demonstrate Lotronex is safe during pregnancy or for women who are breastfeeding, as it may cause harm to the child. Women who are pregnant or breastfeeding should discuss treatment options with their doctor.1

Possible Side Effects when Taking Lotronex

The most common side effects experienced by patients taking Lotronex are constipation, stomach pain and nausea. If a patient experiences constipation while taking Lotronex, they should immediately stop taking it and call their doctor. Rarely, severe complications have been experienced by patients on Lotronex, including severe constipation and ischemic colitis – a condition where blood flow to the intestines is reduced or blocked, which may cause pain and damage to the colon. These conditions can lead to hospitalization, blood transfusions, surgery and even death.2,3

Research on Lotronex

Lotronex was studied for safety and efficacy in five large clinical trials. Two of the studies included women with IBS with no constipation. The other three studies looked at women with severe IBS-D who experience bowel urgency that may restrict their activities. All patients in the studies were randomized to receive either Lotronex or a placebo (harmless pill that produces no physical effect). Women who received Lotronex experienced 10-20% greater relief from their symptoms compared to women who took placebo. The most significant relief was noticed in women with severe IBS-D.1

Additional Treatment Options for IBS

The imbalance of serotonin, which is believed to cause some IBS symptoms, also plays a role in mood and may be the reason why some antidepressants are effective medications for IBS patients.4

The management of IBS symptoms is usually accomplished by a combination of approaches, and determining the best combination for a patient may require some trial and error. There are several medications patients can try, as well as other treatment strategies such as adding exercise, making dietary changes, adding fiber, or trying complementary or alternative medicine.

Written by: Emily Downward | Last reviewed: June 2016.
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