Medications for Chronic Idiopathic Constipation and IBS-C

Chronic idiopathic constipation (CIC) and constipation-predominant irritable bowel syndrome (IBS-C) share similar features and they each respond to some of the same medications. However, there are some differences in how the two conditions are treated on the whole. Chronic idiopathic constipation is often associated with pain and may require treatment for the pain, while IBS-C is more likely to respond to anti-depressants and antispasmodics.

Doctor with patient
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In general, over-the-counter laxatives, which loosen the stool, are used first for both conditions. If first-line treatments are not effective, prescription laxatives and therapies that increase movement of the intestines can be used.

Speak with your doctor before stopping a recommended medication or trying a new one, particularly if you are experiencing new or worsening symptoms.


Miralax does not require a prescription. It is a laxative powder that your doctor may recommend to ease your constipation. Miralax draws water into the stool, softening it and inducing the urge for a bowel movement.

Milk of Magnesia

A liquid or tablet laxative, Milk of Magnesia is an over-the-counter product that stimulates movement of the intestines and draws fluid into the intestines.


Lactulose is a prescription laxative and stool softener. Brand names include Cephulac, Chronulac, Constilac, Cholac, Constulose, Duphalac, Enulose, Generlac, and Kristalose. 

Lactulose is a man-made sugar that is broken down by bacteria in the intestines. The drug is considered an osmotic laxative because of the way it draws fluid into the intestines (osmosis). The increase in water softens and bulks the stool, normalizing the consistency. The higher volume of stool also helps to stimulate colon motility, encouraging a bowel movement.

Lactulose is generally recommended for short-term use. It can cause bloating and gas.


Amitiza (lubiprostone) is a prescription medication approved by the Food and Drug Administration (FDA) for the treatment of IBS-C and CIC. It is a pill that should be taken with food. It increases the volume of fluid in the intestines, which eases the passage of stool.

The medication works by activating proteins involved in transporting chloride, and it is described as a chloride channel activator. Amitiza usually relieves symptoms within 24 hours.

You should not take Amitiza if you have a bowel obstruction, experience severe diarrhea, or are pregnant or breastfeeding.


Approved by the FDA for the treatment of chronic idiopathic constipation and IBS-C, Trulance (plecanatide) is believed to increase fluid in the intestines and to decrease pain. It activates guanylate cyclase C (GC-C), an enzyme that is involved in regulating fluid in the intestines by increasing chloride.


Linzess (linaclotide) is FDA approved for the treatment of IBS-C and CIC. It is thought to work by increasing the amount of fluid in the large intestine, which results in an increased number of bowel movements and decreased abdominal pain. This medication, like plecanatide, is characterized as a guanylate cyclase-C agonist.


Prucalopride is classified as a 5-HT agonist because it activates receptors for the neurotransmitter serotonin (5-HT).

Pain Medications

Often, pain medications, particularly narcotics and opioids, increase constipation. Over-the-counter acetaminophen, as well as prescription anticonvulsants, can relieve the pain of chronic idiopathic constipation. IBS-C is not typically characterized by pain, so this is most appropriate for CIC.

Antidepressants and Antispasmodics

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

Antidepressants classified as selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants are often used in the treatment of IBS-C and less often for chronic idiopathic constipation. SSRIs include Prozac (fluoxetine) and Zoloft (sertraline), while tricyclic antidepressants include Norpramin (desipramine).

Antispasmodics are muscle relaxants. Bentyl (dicyclomine) and Levsin (hyoscyamine) are antispasmodics used for the treatment of IBS-C. As with antidepressants, antispasmodics are not as effective for the treatment of chronic idiopathic constipation and are not frequently used for this condition.

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  2. U.S. Food and Drug Administration. Amitiza (lubiprostone) Capsules. Updated November 2012.