Certain breast cancer treatments are known to have diarrhea as a side effect. Until you start taking a medication, you can’t really predict whether you’ll have diarrhea. However, there are steps you can take to be ready for it and help yourself if diarrhea starts.

Diarrhea is a condition where you have loose, watery stools more than 3 times in 1 day. You may also have cramps, bloating, and nausea, and feel like you urgently need to have a bowel movement. Diarrhea happens when the water in your intestine is not being absorbed back into your body.

Some breast cancer treatments are known to have diarrhea as a side effect. The biggest culprits are certain forms of chemotherapy and some targeted therapies, but hormonal therapies can also cause diarrhea. The bone-strengthening medications known as bisphosphonates — taken by some women during and after breast cancer treatment — can have this side effect.

Some anti-cancer therapies can impact your immune system, too, which could make you more vulnerable to the effects of a stomach virus or foodborne illness.

Diarrhea — Breast Cancer Treatment Side Effects

Jan. 9, 2020
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Breast cancer treatments that can cause diarrhea

Several breast cancer treatments can cause diarrhea:

Bisphosphonates, medicines taken by some women to strengthen their bones during and after breast cancer treatment, also can cause diarrhea. The most common bisphosphonates are:

Diarrhea is also a common side effect of many pain medicines, including ibuprofen and morphine.


Managing diarrhea

Until you start taking a medication, you can’t really predict whether you’ll have diarrhea, and if so, whether it will be a mild nuisance or a major problem. However, there are steps you can take now to be ready for it and help yourself if diarrhea strikes. If you have diarrhea that lasts for more than 48 hours, call your doctor right away. Medicines are available to help.

Here are some tips for getting ahead of this side effect and managing it when it occurs.

Before starting treatment

Ask your doctor what other patients’ experience has been and when to call the office for help. For a given treatment, how commonly have his or her patients experienced diarrhea, and has it been mild, moderate, or severe? Does it tend to get better or worse over time? Ask about when you should call the office and who can help you if you experience diarrhea. Although patients often hesitate to report side effects, your treatment team is there to help.

Other topics to discuss with your doctor are:

  • Whether you’re taking other medications that cause constipation — such as anti-nausea medications or pain medications — and how to manage that along with treatment-related diarrhea

  • Whether you’re taking other medications that could make diarrhea worse

  • Any history of medical conditions that increase the risk of diarrhea, such as irritable bowel syndrome, Crohn’s disease, colitis (inflammation of the colon), diverticulosis (when small pockets form in the intestinal wall), or previous bowel surgery

Be prepared with the over-the-counter anti-diarrheal medication Imodium (chemical name: loperamide) and bland foods that can help. If diarrhea is likely, buy a package of Imodium in advance and stock some foods that can help (see below for tips). One common recommendation for easing diarrhea is the “BRAT” diet: bananas, rice, applesauce, and toast.

Be ready to keep a diary of what you eat and any episodes of diarrhea. Whether you use a journal, calendar, notepad, or computer, record any episodes of diarrhea and their severity (urgency, amount, watery diarrhea or soft stool?). Also track what you eat and drink. This might feel like an odd thing to do, but it will help you figure out when diarrhea tends to occur, if certain foods are — or aren’t — helping, and whether it gets better or worse over time. You’ll also be more prepared to discuss your symptoms with the treatment team, which can help them figure out how to manage the diarrhea.

Community member cse70 offers this advice: “Keep a diary. Even if the first episode of diarrhea surprises you after your first chemo treatment, you will be able to plan for the next ones. I was fortunate enough to take off work on my ‘Big D’ days!”

“Keep a food diary to track your really bad episodes,” adds Kdrake1007, who experienced this side effect with Verzenio (chemical name: abemaciclib). “I’ve found that coffee is a big NO for me. It causes severe cramping and multiple episodes of diarrhea for a day after I drink it. Tea and other drinks with caffeine don’t cause the same reaction. Salad also often causes problems. I’ve pretty much learned to manage it … I always have Imodium with me and will take it before really big events, like my daughter’s wedding.”

During treatment: Eating tips to manage diarrhea

Drink lots of fluid. Try a clear liquid diet — water, weak herbal tea, apple juice, clear broth, frozen pops, or plain gelatin — as soon as diarrhea starts or you feel like it's going to start. Clear liquids keep the bowels from working too hard and help prevent irritation. After a day or two, start adding in low-fiber solid foods. Try to drink at least a cup of liquid after each bout of diarrhea so you don't become dehydrated. Signs of dehydration can include excessive thirst, dry mouth, headache, feeling sleepy, and low output of urine that is dark yellow or even amber in color.

Eat small, frequent meals. Instead of three main meals, eat smaller amounts throughout the day. Your body may find smaller amounts easier to digest.

This helped Community member WC3 during chemo: “Maybe I just lucked out but I didn't have much diarrhea. It would just come on suddenly when I did. But what helped to reduce the amount I had was to keep my portion size small. I snacked more than ate large meals … and I couldn't eat much in general. If I had to be pre-emptive, I would take Imodium.”

Choose foods that can help with diarrhea. For example, foods that are high in pectin, such as applesauce, bananas, and yogurt, can be helpful. Pectin, a water-soluble fiber, helps reduce diarrhea. Also choose foods high in potassium, such as fruit juices, sports drinks, potatoes without the skin, and bananas. Your body tends to lose potassium when you have diarrhea. Unless you’re on a low-salt diet, high-sodium foods such as soups, broths, sports drinks, crackers, and pretzels can help you retain water so you don't get dehydrated.

Get enough protein. Try lean baked beef, pork, turkey, fish or chicken or well-cooked eggs or tofu. Greek yogurt is high in protein too. Getting more protein can help you avoid fatigue.

If you like certain vegetables, eat them cooked, not raw, and remove the peels from vegetables and fruits. Some raw fruits and vegetables can make diarrhea worse. Boil vegetables and try soups made with cooked asparagus tips, beets, carrots, peeled zucchini, mushrooms, celery, or other vegetables. Remove the skin from foods like potatoes and apples.

Avoid tobacco products, chewing gum, and foods and drinks that can make diarrhea worse, such as:

  • Caffeine or alcohol

  • Carbonated drinks

  • Milk and milk products

  • Nuts, whole-grain breads, bran, and other super high-fiber foods

  • High-fat, fried, greasy, and/or rich foods

SpecialK talks about how adjustments to her diet helped her: “I had 10 days of Big D after each chemo. Not terrible, but bad enough to not leave the house unless I had to. Second 10 days before next infusion were normal … I did not really use any meds, just let things run their course but monitored how I was feeling, drank a lot so I did not become dehydrated, ate BRAT foods, avoided anything high fiber and carbonated beverages or things with caffeine.”

During treatment: Other tips for managing diarrhea

Try Imodium or FiberCon. Dietary changes aren’t always enough to control diarrhea. And of course there will be times when you know you have to be diarrhea-free (such as social events, meetings, special occasions, or air travel). Many people report that Imodium helps — but it often takes some time to find the dosage and timing that controls diarrhea without causing constipation.

Community member pajim describes how she found the right dose: “Aah, Verzenio. When I started it, the pharmacy told me to take two Imodium as soon as the diarrhea started and one every 12 hours thereafter.

"That, simply, was a disaster. Maybe it works for some people but not for me. There was war in my intestines. The cramping, the pain … What helped me was to decide that ‘normal stools’ was not the goal. The goal was to avoid ‘I have to go to the bathroom right now or else.’ So I took Imodium in small doses as needed and dealt with generally loose stools. When they got too loose I took another 1/2 Imodium. I think how much to medicate this particular side effect is highly individually variable.”

BellasMomToo agrees: “Imodium helped, but I had to be careful not to take too much Imodium for fear of getting constipated because I had diverticulosis (pockets in my colon). Then the anti-nausea drugs would make me constipated. So it was quite the balancing act — some days diarrhea, other days constipation.”

Although high-fiber foods can make diarrhea worse, some Community members have found that the supplement FiberCon (calcium polycarbophil) helps. Although it’s marketed as a remedy for constipation, it also can help to bulk up the stools, which may improve diarrhea.

“For me, the suggested non-prescription Imodium worked too well: everything stopped up and then there were terrible abdominal cramps, etc., as it wore off,” says Community member Vlnrph. “By taking two FiberCon or the much less expensive calcium polycarbophil daily, I get absorption of excess fluid which remains in the gastrointestinal tract so that it bulks up the stool without creating constipation.”

Use protective pads and be prepared. At least initially, until you figure out how to manage the diarrhea or treat it with your doctor’s help, you might find it helpful to wear protective pads or disposable underwear when you go to bed at night or plan to be out of the house. Carry some with you as part of an “emergency pack” that includes a change of underwear and clothes, wet wipes, and hand sanitizer.

Moonflwr912 shares her thoughts: “I wish whoever has this side effect big hugs, and the knowledge that this, too, shall pass. Too slowly, but it will. I went to diapers for every day. Cried when I did, but saved me time, laundry, and embarrassment. Kept a change of clothes in the car. Carried them in a small zippered bag, along with portable wipes, and Aquaphor.”

Soothe irritation in the anal area. Frequent bowel movements and wiping can irritate your bottom. Instead of using toilet paper, clean your anal area with a mild soap after each bowel movement, rinse well with warm water using a squirt bottle, and pat dry. You might consider buying an affordable bidet toilet attachment as an alternative. After cleaning, apply a water-repellent ointment, such as petroleum jelly or Aquaphor, to the area. Sitting in a tub of warm water or a sitz bath (a shallow insert you can rest on your toilet and fill with warm water) also may help reduce any discomfort you may have.

If diarrhea persists or is worse than you can handle, talk to your doctor. He or she might be able to adjust your treatment plan, changing the dose or type of medication. Another option is prescription medication to control the diarrhea, such as Lomotil (chemical name: diphenoxylate and atropine); Carafate (chemical name: sucralfate); or somatostatin, which is given by injection. Cholesterol-lowering medications such as cholestyramine and Welchol (chemical name: colesevelam) also can be helpful for persistent diarrhea. There may be some trial and error as you figure out what works for you.

Mustlovepoodles writes: “I had bad diarrhea from the very first chemo and nothing would touch it. Eight or nine watery explosive stools a day. I was a community health nurse, so I was in my car driving long distances every day. I had a few close calls on the road, so I always carried extra clothes, just in case. Finally, I went to a GI specialist and he put me on a very old cholesterol drug called Welchol. The main side effect is constipation. It was perfect for my situation. I went from having multiple watery stools (and torn-up butt!) to having one or two merely soft, almost normal stools every day.”

If you have diarrhea for 2 days or more, feel dehydrated, or have other concerning symptoms, seek immediate medical attention. Call your doctor’s office or go straight to the nearest emergency room if you have diarrhea along with symptoms such as fever, blood in the stool, and/or severe abdominal pain and/or bloating. Other symptoms of concern are:

  • Extreme fatigue

  • Dizziness or confusion

  • Inability to drink or eat

You can actually be dehydrated without even realizing it, and this can be serious. You may need intravenous fluids to help you get back on track.

“If someone is having a lot of diarrhea and is having trouble eating or particularly drinking, or if they're getting dizzy, call the doctor’s office immediately. Dehydration is nothing to mess around with,” notes Community member pajim. “I know because I lost 25 pounds in 5 days — it was over a weekend and took us a few days to figure out what was happening. Should have yelled for help two days before I actually did."

— Last updated on July 27, 2022, 1:43 PM

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