Effects on the Gastrointestinal System

The cells of the gastrointestinal tract are metabolically very active and are therefore quite susceptible to the damaging effects of cytotoxic drugs. Commonly occurring chemotherapy-induced toxicities affecting the gastrointestinal system include anorexia, stomatitis, nausea and vomiting, constipation, and diarrhea. Toxic effects to the gastrointestinal system can cause life-threatening infection, malnutrition, and fluid and electrolyte disturbances.


Anorexia refers to a decrease or complete loss of appetite. Most chemotherapy drugs cause some degree of anorexia. Anorexia can be mild, or it may lead to cachexia, a severe form of malnutrition. Cancer treatments and the cancer itself can alter the way some food tastes. Taste changes may include a dislike for or an increased desire for meat and sweet foods, a dislike of foods with bitter tastes, tomatoes and tomato products, and a metallic or medicinal taste in the mouth. These changes occur because chemotherapy drugs can alter the taste receptor cells in the mouth that are responsible for flavor sensations. Decreased appetite is generally temporary and returns when chemotherapy is finished. Medications can be prescribed to help improve appetite.

Management strategies for anorexia include:

a. Obtaining the patient’s baseline height and weight.
b. Teaching the patient to report weight loss.
c. Monitoring serum protein and albumin levels.
d. Analyzing the patient’s dietary intake, including asking the patient to keep a 3 day food intake journal.
e. Urging the patient to eat high-protein, high-calorie foods.
f. Encouraging small, frequent meals in a pleasant atmosphere.
g. Instructing the patient to take appetite stimulants as ordered.

Toxicities affecting the gastrointestinal system can involve potentially life threatening complications such as infection and malnutrition.


Stomatitis refers to the development of inflammation and sores in the mouth. Approximately 40% of cancer patients develop stomatitis. Similar changes in the throat or the esophagus are called pharyngitis and esophagitis. Stomatitis, pharyngitis, and esophagitis can lead to bleeding, painful ulcerations, and potentially life-threatening infection. The first signs of mouth sores occur when the lining of the mouth appears pale and dry. Later, the mouth, gums, and throat feel sore and become red and inflamed. The tongue may be coated and swollen, leading to difficulty swallowing, eating, and talking. Mouth, throat, and esophageal sores are temporary and usually develop 5-14 days after receiving chemotherapy. Other alterations in the oral mucosa include dryness of the mouth (xerostomia), unusual taste perceptions, and a decrease in taste perception.

Approximately 5-10% of patients receiving chemotherapy develop stomatitis.

Stomatitis can lead to life-threatening problems such as sepsis and malnutrition. Factors that increase the incidence of stomatitis include the type of cancer, the patient’s age and oral health, and the type of drug used. Drugs most commonly associated with stomatitis include antimetabolites such as 5-fluorouracil and methotrexate and the antitumor antibiotics doxorubicin and actinomycin.

Management strategies for stomatitis include:

a. Doing an oral assessment daily.
b. Referring the patient for a dental consultation before chemotherapy begins.
c. Performing good oral hygiene every 4 hours. If mild stomatitis occurs, mouth care should be done every 4 hours around the clock. Mouth care should be done every 2 hours day and night if the patient develops severe stomatitis.
d. Brushing the teeth gently with a soft toothbrush after meals and at bedtime.
e. Using waxed floss rather than unwaxed floss, or temporarily stopping flossing if stomatitis is severe.
f. Avoiding using commercial mouthwashes containing alcohol that dry and irritate tissues.
g. Rinsing the mouth with warm saline or with sodium bicarbonate rinses. Hydrogen peroxide mouthwashes are not recommended because they disturb the normal flora of the mouth and can lead to oral fungal infections.
h. Wearing dentures only if necessary.
i. Eating a high protein diet and drinking 3 liters of fluid daily unless contraindicated.
j. Avoiding hot spicy foods and oral irritants such as alcohol and tobacco.
k. Treating oral infections with antifungal or antiviral agents as ordered.
l. Giving local or systemic anesthetics or pain medications as ordered. For example, 2% viscous xylocaine may be given before meals.
m. Using a topical protective agent to promote healing, such as antacid preparations.
n. If the patient has xerostomia, using a saline substitute or sucking on hard, sugarless candy, and chewing sugarless gum to keep the lips and oral cavity moist.
o. Teaching the patient to notify health care providers if he or she develops a fever above 38 degrees Centigrade or if bleeding and poor oral pain control impair nutritional intake.

Antimetabolites and antitumor antibiotics are the cytotoxic agents most often associated with causing stomatitis.

Nausea and vomiting

Nausea and vomiting is an extremely distressing side effect of cancer chemotherapy treatment. Approximately 70 to 80% of patients receiving cytotoxic drugs have some degree of nausea and vomiting. Chemotherapy drugs cause nausea and vomiting because they both irritate the lining of the stomach and duodenum and stimulate nerves that lead to the vomiting center in the brain. Vomiting can be acute, occurring within minutes to hours after chemotherapy, or delayed, developing or continuing for 24 hours after chemotherapy and sometimes lasting for days. Anticipatory emesis is a conditioned or learned aversion to chemotherapy experienced by approximately 10% to 44% of cancer patients. A patient with anticipatory emesis may start vomiting before chemotherapy. Acute emesis usually begins shortly after treatment. Delayed emesis persists for 1 to 4 days after chemotherapy. Delayed emesis is usually associated with high doses of cisplatin and some combination chemotherapy regimens. Protracted nausea and vomiting can severely affect the patient’s food intake and nutritional status.

Some cytotoxic drugs irritate the lining of the gastrointestinal tract and stimulate the vomiting center in the brain.

Although it is not possible to predict the onset, severity, or duration of nausea and vomiting for individual patients, certain chemotherapy drugs are more likely to cause nausea and vomiting. Examples include cisplatin, dacarbazine, actinomycin-D, mechlorethamine, streptozocin, carboplatin, cyclophosphamide, lomustine, carmustine, daunorubicin, doxorubicin, epirubicin, idarubicin, cyarabine, and ifosfamide.

Some patient characteristics increase the potential for nausea and vomiting. Patient risk factors include age – younger patients have more nausea and vomiting than older patients, female gender, severe emesis during pregnancy, changes in taste perception, prior experiences with motion sickness, and previous nausea and vomiting associated with chemotherapy.

Males have more chemotherapy associated nausea and vomiting than women.

The most effective intervention for nausea and vomiting is prevention, including using both drugs and behavioral interventions such as guided imagery, relaxation, hypnosis, and distraction. Recent advances in antiemetic (antivomiting) therapy include drugs that can decrease the incidence and distress associated with nausea and vomiting. Serotonin receptor antagonists are an important class of antiemetic drugs that provide effective emetic control with minimal side effects. These drugs, given before chemotherapy, include dolasetron, granisetron, ondasetron, and tropisetron. Many other drugs are used alone or in combination to prevent or decrease nausea and vomiting.

The most effective intervention for chemotherapy associated nausea and vomiting is prevention.

Management strategies for nausea and vomiting include:

a. Trying to control nausea and vomiting before it occurs.
b. Using pharmacological agents such as serotonin receptor antagonists and other anti-emetic drugs.
c. Eating foods cold or at room temperature. Smells from hot foods may cause nausea and vomiting.
d. Eating light, frequent meals throughout the day.
e. Rinsing the mouth often, especially before and after meals.
f. Avoiding foods that are spicy, greasy, or have strong tastes or odors.
g. Drinking clear cold liquids such as ginger tea.
h. Avoiding food intake 1 to 2 hours before chemotherapy.
i. Minimizing stimuli that might cause a vomiting response, such as the sight of other patients vomiting.
j. Using distraction or guided imagery.

Both pharmacologic and non-pharmacologic strategies are useful in controlling chemotherapy associated nausea and vomiting.


Constipation affects 50% of people with cancer and 78% of patients with advanced disease. Constipation can be caused by the cancer itself, changes in food and fluid intake, decreases in activity, and by some cytotoxic drugs and other drugs used to treat cancer symptoms. Agents that commonly produce constipation are the vinca alkaloid drugs vincristine and vinblastine, opioids given for pain relief, and antiemetics, particularly the serotonin receptor antagonists.

Few patients receiving cancer treatment experience constipation.

Management strategies for constipation include:

a. Assessing the patient’s bowel function and elimination pattern.
b. Helping the patient establish a daily bowel program.
c. Encouraging the patient to increase intake of foods rich in fiber and bulk and to drink 8 to 10 glasses of water daily.
d. Encouraging physical activity as tolerated.


Diarrhea is more common than constipation and can cause potentially serious side effects, including dehydration, electrolyte imbalances, and malnutrition. Diarrhea occurs in 75% of people who receive chemotherapy due to damage to the rapidly dividing cells of the gastrointestinal tract. Cytotoxic drugs often associated with causing diarrhea are 5-fluorouracil, methotrexate, docetaxal, and actinomycin-D. Factors affecting diarrhea include which drugs are given, the drug dose, and the length of treatment. Patients who have a stomach tumor, are lactose intolerant, or are receiving radiation therapy in conjunction with chemotherapy have an increased incidence of diarrhea. Diarrhea is managed by pharmacologic interventions with anticholinergic drugs and opioids.

Management strategies for diarrhea include:

a. Assessing the patient for signs and symptoms of diarrhea and dehydration.
b. Assessing the patient’s bowel function and elimination patterns.
c. Monitoring weight, intake and output, and electrolytes.
d. Giving intravenous fluids or electrolytes as ordered.
e. Giving antidiarrheal medications as ordered.
f. Encouraging the patient to eat a low-residue, high-protein, high-calorie diet, increasing fluids, and avoiding foods and substances such as spicy foods, beans, milk, caffeine, alcohol, and tobacco.
g. Instructing the patient to practice good perianal hygiene after each episode of diarrhea.
h. Encouraging rest and decreased activity during periods of diarrhea.

The American Society for Parenteral and Enteral Nutrition - www.nutritioncare.org is an excellent resource for health professsionals and patients.