People receiving certain cancer treatments, such as chemotherapy (chemo), may experience constipation. Doctors sometimes refer to this side effect as chemotherapy-induced constipation. It is one of the most common reasons why doctors will reduce chemo doses or delay or stop treatment.

Although chemo can cause constipation, other factors related to cancer treatment can also contribute to hard or difficult-to-pass stools. These may include changes in diet and fluid intake and reduced physical activity. Certain types of cancers, such as a tumor in the belly or pelvis, can also directly cause constipation.

This article will explain the relationship between chemo and constipation and look at the treatment options.

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Constipation refers to a reduced frequency of bowel movements and hard and dry stools. Researchers suggest that the prevalence of chemotherapy-induced constipation is about 16% among people with cancer. They note that 5% of these individuals have severe constipation, and 11% have moderate constipation.

The underlying reason for chemotherapy-induced constipation is unclear. Doctors suggest that constipation occurs because of a combination of factors associated with chemotherapy. These include:

  • inflammation in the digestive tract
  • disorder in bowel secretions
  • disorder in movements within the digestive tract
  • changes in how the digestive tract responds to the nervous system

Specific chemo drugs associated with constipation include:

  • gemcitabine (Gemzar)
  • oxaliplatin (Eloxatin)
  • thalidomide (Contergan)
  • vinblastin (Velban)
  • vincristine (Oncovin)

Learn about other side effects of chemotherapy here.

People taking chemo may also have to take additional drugs to relieve the side effects, including nausea. Some people may require opioids to help with the pain that cancer can cause. It can, therefore, be challenging for doctors to know exactly which drug is causing constipation.

Tumors in the intestine or pelvis may also cause constipation. Other factors that can contribute to constipation include:

  • lack of physical activity
  • bed rest
  • changes in the diet
  • poor fluid intake

Some people also take vitamins and minerals, such as iron or calcium, during their cancer treatment, and this can also cause constipation.

Although the treatment for chemotherapy-induced constipation is laxatives, people who overuse these drugs may aggravate their condition.

Thyroid problems and depression associated with cancer can also cause constipation.

Alongside medication, people can take steps at home to relieve chemotherapy-induced constipation. These include:

  • engaging in regular physical activity, if possible
  • increasing fluid intake to 8–10 glasses of fluid throughout the day
  • increasing fiber intake by adding whole grains, brown rice, raw fruit and vegetables, legumes and beans, dried fruit, popcorn, seeds, and nuts to the diet

A dietitian can help people choose fiber-rich foods to include in their diet. Sometimes, a fiber supplement can help.

Learn more about high fiber foods here.

People should also log their bowel movements in a journal, along with details about their diet and fluid intake. With this information, doctors can help make recommendations to improve bowel movements.

Some natural laxatives include:

Hot drinks, such as cocoa, tea, or hot water with lemon, can help stimulate the bowels.

Learn more about the best foods to eat for constipation here.

Other tips include:

  • going to the bathroom as soon as there is an urge
  • avoiding foods that cause gas — such as apples, avocados, beans, peas, cabbage, broccoli, milk, and sodas — until after the alleviation of constipation
  • avoiding chewing gum
  • refraining from using straws
  • avoiding foods that cause constipation, such as eggs and cheese

Learn more about home remedies for constipation here.

Along with general recommendations of increased dietary fiber, fluids, and exercise, doctors may recommend over-the-counter or prescription medications. Oral and rectal bulk-forming, emollient, osmotic, stimulant, and lubricant laxatives may help.

Learn about the differences between stool softeners and laxatives here.

Bulk-forming laxatives

Bulk-forming laxatives work by swelling inside the intestines, allowing the bowel to expand slightly and promoting the passage of stool. The slight expansion of the intestine stimulates movements within the bowel and reduces the time it takes stool to pass. Bulk-forming laxatives include:

  • methylcellulose (Citrucel)
  • psyllium (Metamucil)
  • polycarbophil (Fiber Lax)

Osmotic laxatives

Osmotic laxatives include:

These laxatives help relieve constipation by drawing fluid into the intestine and keeping it there. Osmotic laxatives may promote bowel movements within 24–72 hours.

Emollient laxatives

Emollient laxatives are also called stool softeners. These drugs work by increasing intestinal fluids and enabling the mixing of fat and watery substances in the bowel, which softens hard and dry stools and makes them easier to pass.

Emollient laxatives are ineffective if a lack of movement within the intestine is responsible for constipation. Often, doctors will recommend taking emollient laxatives with bulk-forming agents. Examples of emollient laxatives include:

  • docusate calcium
  • docusate sodium
  • docusate potassium

Stimulant laxatives

These laxatives stimulate neurons within the intestine, causing contractions that push stool along. Research shows that these laxatives work better than enemas and bulk-forming agents and are often effective for constipation resulting from opioid use. Examples of stimulant laxatives include:

  • sodium picosulfate (Picodan)
  • sennosides (Senokot)
  • castor oil

Lubricant laxatives

Lubricant laxatives work by coating the stool and the rectum in a slippery film to promote easier bowel movements. The most common lubricant laxative is mineral oil, which people can use orally or rectally.

Rectal laxatives

Doctors only recommend these drugs with manual stimulation for fecal impaction or neurogenic bowel dysfunction. The most commonly used rectal laxatives are bisacodyl suppositories and glycerin suppositories.

People should avoid using enemas or suppositories without seeking medical advice first. It is important always to ask a member of the cancer care team before trying any laxative.

People taking chemo who have constipation should generally see a doctor if they have not had a bowel movement in 3 days. However, this duration depends on the type of chemo and the protocols at the specific cancer center. Some cancer care teams may specify a different interval between bowel movements when medical attention is necessary.

People taking laxatives or stool softeners to relieve constipation should see a doctor if the medication is not working. If the person does not have a bowel movement within 1–2 days of taking a laxative or stool softener, they require medical attention.

The following symptoms of constipation also require medical attention:

  • blood in or around the anus
  • blood in the stool
  • persistent belly cramps or vomiting
  • loose or watery stools

The cancer care team may also specify additional symptoms with constipation that require medical attention. People should follow the instructions that their healthcare team provides.

Frequent complications of passing hard, dry stool include:

Some people with severe constipation may develop obstipation, which is severe persistent constipation. Obstipation can have life threatening consequences, such as blocking the bowel.

Completely unpassable stools can increase the pressure in the bowel and cause reduced blood flow and tissue death. Sometimes, the intestine may burst.

Learn when constipation is an emergency here.

Constipation is common when people with cancer receive chemotherapy. Constipation can occur for many different reasons. For example, some chemotherapy drugs or reduced activity or fluid intake can cause constipation.

Exercising, eating fiber, and taking in fluids are ways to encourage bowel movements naturally. Sometimes, people need medication to relieve constipation. Drug options may include bulk-forming, emollient, stimulant, and osmotic laxatives.

Cancer care teams provide guidelines on managing constipation for people to follow.