Irritable bowel syndrome (IBS) can be diagnosed based on symptoms. A doctor diagnoses IBS when a person has the typical symptoms of the disorder and, if needed, tests have ruled out other possible causes.
Most people won’t need tests, but some people may because of their age and symptoms. The amount of testing you get depends on several things: your age, how your symptoms come on and how severe they are, and how you respond to your first treatment.
Tests may include:
- Medical history and physical exam.
- A blood test for celiac disease.
- Complete blood count (CBC).
- Sedimentation rate, which checks for inflammation in the body.
- Stool analysis.
Thyroid function tests and other tests, such as colonoscopy, are sometimes done.
Medicine may be used along with lifestyle changes to manage symptoms of irritable bowel syndrome (IBS). It may be prescribed to treat moderate to severe pain, diarrhea, or constipation that does not respond to home treatment.
Medicine can help relieve your symptoms enough to prevent them from interfering with your daily activities. It may not be possible to eliminate your symptoms.
In most cases, the choice of medicine is based on your most troublesome symptom. For example, if diarrhea is the most bothersome symptom, using antidiarrheals or anticholinergics may be helpful.
Few medicines have proved consistently helpful, and all medicines have side effects. So medicine should be used for specific symptoms that disrupt your normal daily activities.
If you also have another illness, such as depression, that triggers symptoms of irritable bowel syndrome, medicine for that illness may be needed.
Medicines that may be used to treat severe diarrhea that does not improve with home treatment include:
- Antidiarrheals, including atropine and diphenoxylate (such as Lomotil) and loperamide (such as Imodium).
- Bile acid binding agents, including cholestyramine (such as Prevalite).
- Rifaximin (Xifaxan), which has been shown to help people who have diarrhea and bloating as their worst symptoms. In one study, people who had fewer symptoms after 2 weeks of taking rifaximin continued to have fewer symptoms for 10 weeks after stopping the medicine. But rifaximin is very expensive, and more research needs to be done. There are still many questions about this treatment, including who will get the most benefit, how long the effect will last, and whether retreatment will work when symptoms come back.5
- Alosetron (Lotronex), which is used for some women who have severe diarrhea. This medicine has been shown to contribute to ischemic bowel disease. Specific guidelines for the use of alosetron require doctors who prescribe it to sign a certificate and patients to sign a consent form.
There are many medicines for severe constipation that doesn’t improve with home treatment. Most of these medicines are available without a prescription and are okay to take once in a while. Check with your doctor before you use any of these medicines every day for constipation. Medicines for constipation include:
- Osmotic laxatives (such as Milk of Magnesia and nonabsorbable sugars such as lactulose).
- Polyethylene glycol (such as MiraLax).
- Stimulant laxatives (such as Senokot).
- Linaclotide (Linzess).
- Lubiprostone (Amitiza).
Pain and cramping
The following medicines may be used for long-term pain and cramping:
- Anticholinergics (antispasmodics). These include dicyclomine (Bentyl).
- Antidepressants, including desipramine (such as Norpramin). In low doses, they can help with pain caused by IBS.
The following medicines may be used if your IBS causes you to have anxiety or depression:
- Antidepressants, including fluoxetine (such as Prozac). They are especially helpful if you have depression and IBS.
- Antianxiety agents, including diazepam (such as Valium). These can be used short-term to help with anxiety if it makes your IBS symptoms worse.