8 Dolasetron Side Effects You Should Know About

Dolasetron (Anzemet) is a medication that prevents chemotherapy-induced nausea and vomiting (CINV). It's a brand-name-only medication that's usually taken before you receive chemotherapy. It belongs to a group of medications called serotonin receptor antagonists. Other serotonin receptor antagonists include ondansetron (Zofran) and palonosetron.

Serotonin is a chemical in the body that has many roles. This includes triggering nausea and vomiting when it attaches to certain binding sites (receptors) in the gastrointestinal tract and the brain. Serotonin antagonists work by blocking serotonin from attaching to these receptors. They help prevent CINV when these medications are given before chemotherapy. 

Like most medications, dolasetron can cause mild side effects. But some dolasetron side effects can also be more serious (and more rare). Below, we’ll cover eight of the most notable side effects that you should know about. But keep in mind, this is not a complete list. So before starting dolasetron, talk with your healthcare provider and pharmacist about possible side effects.

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1. Headache

Headache is the most common side effect of dolasetron. And it’s more likely with higher doses. 

If you're having headaches with dolasetron, talk to your healthcare provider. They might recommend an over-the-counter (OTC) pain reliever, like acetaminophen (Tylenol) or ibuprofen (Advil, Motrin). But don’t take anything without talking to them first. It’s not always a good idea to use a pain reliever before chemotherapy treatment. So you’ll want your provider’s approval first. 

2. Tiredness

Dolasetron can make you feel more tired than usual. This tends to be more common with higher doses. 

If you’re taking dolasetron, you're likely receiving chemotherapy too. Chemotherapy can be hard on the body and also make you feel tired. If you’re experiencing fatigue, try your best to have a consistent sleep schedule. Routine exercise and eating a healthy diet full of fruits and vegetables can also be energizing.

3. Diarrhea

Dolasetron may also cause diarrhea. Common symptoms of diarrhea include bloating, watery stools, and abdominal pain. While this can be an uncomfortable side effect, there are few things that may help relieve it.

First, diarrhea can make you dehydrated. So make sure to drink plenty of water throughout the day. Avoiding certain foods — like fatty, fried, or high-fiber food — may also help. You can also talk to your healthcare provider or pharmacist about using an OTC medication like loperamide (Imodium A-D). If that doesn’t work, let your provider know right away. 

4. Slowed or faster heart rate

Dolasetron can affect how quickly your heart beats. This can lead to bradycardia (slow heart rate). It can also lead to tachycardia (fast heart rate), though it’s less likely. Typically, a heartbeat of less than 60 beats per minute is considered too slow. A heartbeat of more than 100 beats per minute is considered too fast. 

Bradycardia and tachycardia don't always cause symptoms. You may not realize that your heart rate has changed. But if you do experience symptoms, you might feel dizziness, a sensation of skipped heartbeats, or shortness of breath.

If you develop symptoms of bradycardia or tachycardia, talk to your healthcare provider right away. 

5. Stomach upset

Dolasetron may cause stomach upset. Symptoms include bloating, abdominal pain, and feeling full quickly when eating. This can be quite uncomfortable. But there might be things you can do to relieve symptoms of stomach discomfort.

For example, you can try avoiding foods that are known to make bloating worse. This includes dairy products, carbonated beverages, and beans. You can try eating more slowly and having smaller but more frequent meals throughout the day. And OTC medications may also help. Simethicone (Gas-X) is one example of a medication that may relieve bloating.

If your upset stomach continues while taking dolasetron, talk to your healthcare provider. They can help you check whether something else might be going on.

6. Pain

Some people taking dolasetron may experience general body pain. It’s more likely with higher doses of dolasetron.

You may be able to manage pain with OTC medications like acetaminophen or ibuprofen. But before starting an OTC product, you should talk to your healthcare provider first. It’s common for many types of cancer to cause pain. So you may need to talk to a cancer specialist about pain relief.

7. Serious heart problems

Dolasetron can cause an abnormal heart rhythm (arrhythmia). One way it can do this is by making the “QT interval” last longer. The QT interval is the period in time when your heart is resting during a heartbeat.

Previously, dolasetron was available in an intravenous (IV) form. In 2010, the FDA warned against using IV dolasetron for CINV due to the risk of causing arrhythmia. Dolasetron tablets are less likely to cause arrhythmia, but it’s still possible. It’s more likely at higher doses or if you take other medications that lengthen the QT interval. What’s more, it's more likely with certain heart conditions like congenital long QT syndrome — or if you have low magnesium or potassium levels. Blood levels of these electrolytes should be checked before starting dolasetron.

Dolasetron can also have other serious heart problems. This includes cardiac arrest (when your heart stops suddenly). Serious heart problems are more likely in older adults or people living with heart disease. It’s also more common with certain medications that can affect the heart in a similar way as dolasetron. This includes verapamil and quinidine.

If you start to experience symptoms like chest pain or trouble breathing, seek immediate medical attention.

8. Serotonin syndrome

Another one of serotonin’s roles is determining your mood. But if you have too much serotonin in the brain, it can become dangerous. This is known as serotonin syndrome. 

Serotonin syndrome usually only occurs if you're taking multiple medications that increase serotonin. Many medications, including dolasetron, can increase serotonin. Other common medications that raise serotonin include selective serotonin reuptake inhibitors (SSRIs). 

Serotonin syndrome is usually mild. Mild symptoms include a fast heart rate, tremor and sweating. But serotonin syndrome can be more severe, too. Severe symptoms include confusion, high fever, and high blood pressure.

Serotonin syndrome may go away on its own if you stop the medications that are increasing serotonin. But you shouldn’t do this without talking to your healthcare provider first. If you experience any severe symptoms of serotonin syndrome, seek emergency care.

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Written by:

Makaela Premont, PharmD

Makaela Premont, PharmD, is a pharmacist and the founder of uniquelymickie.com, a website dedicated to helping pharmacy students and pharmacists create a life that they enjoy. She received her Doctorate of Pharmacy from the University of South Carolina and is a licensed pharmacist in North Carolina.

Edited by:

Amy B. Gragnolati, PharmD, BCPS

Amy Gragnolati, PharmD, BCPS, is a pharmacy editor for GoodRx. Amy currently holds her pharmacist license in Georgia and California.

Reviewed by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

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