Medications for Chronic Functional Constipation and IBS-C

Chronic functional constipation (also called "chronic idiopathic constipation" or "CIC") and constipation-predominant irritable bowel syndrome (IBS-C) share similar features and are treated with some of the same medications. Both conditions are classified as functional gastrointestinal disorders, specifically as functional bowel disorders.

Doctor with patient
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In general, dietary and behavioral approaches like increasing dietary fiber and water, listening to your body's cues to defecate, and increasing physical activity are recommended first. If those prove ineffective, over-the-counter laxatives may provide some relief.

If over-the-counter methods don't provide enough relief, some people need prescription medications that increase fluid in their intestines and stimulate the movement of their bowels.

Over-the-Counter Medications for Constipation

Over-the-counter (OTC) remedies work well for many people with constipation. These have the advantage of being readily available from the store, without a prescription.

Bulk-Forming Laxatives

Fiber products like psyllium (Konsyl, Metamucil, Perdiem) are not absorbed by the intestines and therefore "bulk up" the stool. Other bulk-forming laxatives include:

  • Methylcellulose (Citrucel)
  • Calcium polycarbophil (FiberCon, Fiber-Lax, Mitrolan)
  • Wheat dextrin (Benefiber)

In its 2021 clinical guidelines for IBS, the American College of Gastroenterology (ACG) recommends soluble fiber for IBS, but not insoluble fiber. Soluble fiber is found in psyllium, oat bran, barley, and beans. Insoluble fiber is found in wheat bran, whole grains, and some vegetables.

Psyllium has the added advantage of not fermenting well in the gut, because foods that ferment in the colon can lead to extra gas and liquid, potentially making symptoms worse for people with IBS-C.

Therefore, any of the above bulk-forming laxatives may help with constipation, but you may get the best results from psyllium (also known as "ispaghula") if you have IBS-C.

Osmotic Laxatives

Osmotic laxatives draw fluid into the intestines by osmosis. The increase in intestinal water softens and bulks the stool, normalizing the consistency. There are a few common types of osmotic laxatives.

Miralax (polyethylene glycol, aka "PEG") is a laxative powder that your healthcare provider may recommend to ease your constipation. Miralax draws water into the stool, softening it and inducing the urge for a bowel movement.

The ACG's 2021 IBS guidelines advise against the use of PEG alone for the treatment of constipation present in IBS-C, stating that it does not appear to help with abdominal pain symptoms. Even so, they acknowledge that it can be a helpful and inexpensive first-line treatment for constipation, with a long safety record.

Sorbitol is a sugar alcohol known as a "polyol." Although it may be helpful for some people for constipation, it should be noted that it can cause bloating and gas in some people and is not recommended for people with IBS who are trying to follow a low-FODMAP diet.

Saline laxatives like magnesium hydroxide (Milk of Magnesia), magnesium citrate (Evac-Q-Mag) and sodium phosphate have long records of use for constipation. Saline laxatives can cause problems in the balance between water and electrolytes in the body if used more than directed.

Some people have had life-threatening kidney failure and have even died after taking more than the recommended dose of OSP.

Stimulant Laxatives

Stimulant laxatives work by causing the walls of the intestine to contract, which pushes the stool along. They can cause cramping and there is concern that long-term use may cause damage to the intestinal wall, both of which are reasons they may not be a good option for people already experiencing abdominal pain from IBS-C.

Examples of stimulant laxatives include:

  • Senna (Ex-Lax, Senokot)
  • Bisacodyl (Correctol, Dulcolax)

Lubricant/Emolient Laxatives

Some people take mineral oil internally as a laxative, because it lubricates the walls of the intestines. Healthcare providers advise that there are safer remedies to try, and that long-term use of mineral oil may lead to nutritional deficiencies, plus other problems such as leaking mineral oil out of your anus.

Prescription Medications for Functional Constipation and IBS-C

If OTC remedies are ineffective, you may need a prescription. See your provider about whether one of the medications below might be a good fit for your symptoms.

Prescription Osmotic Laxatives

Lactulose operates like the other osmotic laxatives above, but it is available only by prescription. Brand names include Cephulac, Chronulac, Constilac, Cholac, Constulose, Duphalac, Enulose, Generlac, and Kristalose. 

Lactulose is a man-made disaccharide (a kind of sugar) that is broken down by bacteria in the colon. Because its action doesn't begin until it reaches the colon, it can take 24 to 48 hours to lead to a bowel movement.

Lactulose is generally recommended for short-term use. It can cause bloating and gas, so it may not be a good option for people with IBS-C or people on a low-FODMAP diet.

Chloride Channel Activators

Amitiza (lubiprostone) is a prescription medication approved by the Food and Drug Administration (FDA) for the treatment of IBS-C and functional constipation. It is a pill that should be taken with food, in part to diminish the side effect of nausea. It increases the volume of fluid in the intestines and also increases gut movement (peristalsis), which eases the passage of stool.

Lubiprostone is FDA-approved for the treatment of adults with functional constipation, and also for women with IBS-C. Its safety has not been evaluated for men with IBS-C.

The ACG guidelines recommend its use for IBS-C, and they note that some women respond to the drug better over time. You should not take Amitiza if you have a bowel obstruction or experience severe diarrhea. Safety of use during pregnancy or breastfeeding is uncertain.

Guanylate Cyclase Activators

These drugs also act to increase intestinal fluid and intestinal movement by targeting receptors called guanylate cyclase-C (GC-C) receptors. Both of these medications are approved by the FDA for the treatment of functional constipation and IBS-C, and both are also recommended for IBS-C in the current ACG guidelines:

Trulance (plecanatide) is approved for adults. Because of the risk of diarrhea from the medication, use in children can lead to severe dehydration and is not recommended. Plecanatide can be taken with or without food.

Linzess (linaclotide) should also only be used in adults. It is taken on an empty stomach, at least 30 minutes before the first meal of the day.

5-HT4 Receptor Agonists

Selective serotonin type 4 (5-HT4) receptor agonists act on the receptor sites for the neurotransmitter serotonin in the gastrointestinal (GI) system, which helps to accelerate transit of the stool through the bowel.

Motegrity (prucalopride) was approved by the FDA in 2018 for functional constipation (chronic idiopathic constipation) in adults. Prucalopride shouldn't be used by people with bowel obstructions or inflammatory bowel disease.

Zelnorm (tegaserod) is approved for adult women with IBS-C who are under 65 years of age and are at low risk for a heart attack. Women with more than one of these risk factors shouldn't take tegaserod:

  • Being over 55 years old
  • Being a current smoker
  • Having hypertension or having a treatment history for hypertension
  • Having hyperlipidemia or a history of treatment for hyperlipidemia
  • Having diabetes or a history of diabetes
  • Being obese (defined as a BMI > 30)

Zelnorm's safety has not been evaluated in men.

Certain people are never supposed to take tegaserod, including people who have ever had a heart attack, a stroke, angina, any kind of intestinal ischemia, and people whose liver or kidneys don't work well. In addition, you should not take tegaserod if you have a history of bowel obstruction, active gallbladder disease, or suspected dysfunction with your sphincter of Oddi.

In 2002, Zelnorm was voluntarily withdrawn from the United States market over concerns about increased cardiac events. Zelnorm was reintroduced to the United States Market in March 2019.

The ACG recommends use of Zelnorm for women with IBS-C and low risk of cardiac or ischemic bowel events, but only if other approved medications above have not been successful.


Antidepressants are not formally approved as a treatment for chronic idiopathic constipation or IBS-C. However, they are sometimes prescribed in the treatment of IBS, because they alter intestinal muscle movement and pain, due to their interaction with neurotransmitters in the digestive system.

The main antidepressant classes used in this way are selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants. SSRIs include Prozac (fluoxetine) and Zoloft (sertraline). Tricyclic antidepressants (TCAs) include Elavil (amitriptyline), Pamelor (nortriptylene), Tofranil (imipramine), and Norpramin (despiramine).

The ACG recommends TCAs for IBS patients because they have multiple mechanisms by which they work on IBS-related abdominal pain. They recommend starting at a low dose and then working up until relief is achieved.

Some clinicians recommend SSRIs more often for constipation and TCAs for diarrhea.


Antispasmodics are muscle relaxants. Bentyl (dicyclomine) and Levsin (hyoscyamine) are antispasmodics sometimes used for the treatment of IBS-C. The 2021 ACG guidelines recommend against these antispasmodic medications, stating that there is no quality evidence that they actually work.

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11 Sources
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