Treatment Side Effects – Diarrhea and Constipation

Diarrhea and constipation are common side effects of many medications, including many treatments for lung cancer. Diarrhea is characterized as bowel movements that are loose or unformed stools. Diarrhea may be watery, frequent, or accompanied by abdominal cramping and can lead to dehydration and weakness. Constipation is a decrease in normal bowel movements and is characterized by incomplete passage of stool and/or passage of excessively hard and dry stool. Constipation may cause abdominal pain and a feeling of fullness in the belly.1,2

Why do Diarrhea and Constipation Occur with Cancer Treatment?

Diarrhea and constipation can occur during cancer treatment for several reasons:

  • Chemotherapy drugs work by targeting rapidly dividing cells. Because chemotherapy drugs attack all cells that are dividing quickly, they affect cancer cells as well as normal cells that divide quickly, such as cells in the bone marrow, the lining of the mouth and intestines, and hair follicles. When chemotherapy affects the cells in the digestive tract, like the intestines, it can cause diarrhea or constipation.2,3
  • Targeted therapy focuses on key features present in cancer cells, which hopefully provides treatment with less effect on normal cells. However, targeted therapies still can cause side effects. Side effects are specific to the medication given, but some treatments can cause diarrhea or constipation.2
  • Pain medications can also cause constipation, as they can slow the muscle movement of the digestive tract.2
  • Radiation therapy may also cause diarrhea, particularly if the radiation therapy is directed to the abdomen, pelvis, or lower back.3
  • Having lung cancer is stressful, and stress and anxiety can also cause diarrhea or constipation.3

Managing Diarrhea

Mild diarrhea can often be managed at home by modifying food and drink. Strategies to manage diarrhea include:

  • Drinking clear liquids to replace fluid lost with diarrhea (to prevent dehydration), such as water, broths, apple juice, or sports drinks
  • Avoiding dairy products (milk, cheese, yogurt)
  • Eating low-fiber foods, such as bananas, rice, applesauce and toast
  • Eating foods high in potassium, which is often depleted with diarrhea. Good sources of potassium include bananas, potatoes and apricots
  • Avoiding spicy foods, greasy foods, fried foods, or foods high in fiber and fat
  • Avoid beverages with caffeine or alcohol
  • Try adding probiotic (beneficial bacteria) supplements, such as those containing lactobacillus and bifidobacterium (patients should always discuss with their doctor prior to starting a probiotic)
  • Try over-the-counter medications like Imodium®, Kaopectate®, Maalox® or Pepto-Bismol® (patients should discuss any new medications for diarrhea with their doctor).3,4

If diarrhea becomes more frequent – six or more loose bowel movements a day for more than two days – immediate medical attention should be sought. Additional symptoms that require medical attention include diarrhea with blood in the stool, inability to urinate, inability to drink liquids for more than a day, swollen abdomen, or fever of 100.5°F (38°C) or higher.3,4

Managing Constipation

While every person is different in their pattern of bowel movements, constipation is defined as a pattern of bowel movements that is infrequent or less than normal, for at least a period of time more than one day. There are several techniques that can be helpful for managing constipation, such as:

  • Eating foods that are high in fiber like fruits, whole grain cereals, and vegetables
  • Eating meals at the same times each day
  • Drinking 2-3 liters of non-alcoholic fluids every day
  • Drinking warm liquids
  • Getting regular exercise, 20-30 minutes most days of the week
  • Avoid chewing gum and carbonated drinks 2,4

In addition, there are several supplements and medications that may be recommended by a patient’s doctor that can help relieve constipation, including:

  • Metamucil® or other psyllium husk products
  • Senokot®
  • Dulcolax®
  • Colace®
  • Glycerin suppository
  • Magnesium citrate
  • Phillips® Milk of Magnesia
  • Chronulac® 4

Patients who experience constipation accompanied by pain in the stomach, fever, nausea, vomiting, swollen or hard stomach, or the inability to pass gas should talk to their doctor. In addition, patients who do not have a bowel movement for three days despite following doctor’s orders should seek medical assistance.4

Written by: Emily Downward | Last reviewed: January 2017.
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