Olanzapine for Nausea: Here’s Why This Antipsychotic Prevents Nausea from Chemotherapy

If you or a loved one are receiving chemotherapy, nausea and vomiting may be on your mind — or in your gut. Chemotherapy-induced nausea and vomiting (CINV) happens in up to 80% of people who receive chemotherapy. It can be a distressing and unpleasant side effect to manage. Fortunately, many medications are available to help prevent CINV.

Olanzapine (Zyprexa) is one of them. It can ease nausea and vomiting from chemotherapy. This might come as a surprise since this medication is typically used to treat mental health conditions. But, in some cases, your oncologist may prescribe it off-label if you’re receiving a chemotherapy regimen that’s known to cause nausea and vomiting. 

Here, we’ll go over why olanzapine is sometimes used to manage CINV. We’ll also cover when and how it should be used in addition to side effects it can cause.

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Why can olanzapine prevent chemotherapy-induced nausea and vomiting?

Olanzapine’s ability to counteract CINV stems from how chemotherapy triggers nausea in the first place.

When chemotherapy enters the body, it causes a release of chemicals such as serotonin, dopamine, and substance P. These chemicals go on to stimulate the parts of the gastrointestinal tract and brain, which ultimately triggers nausea and vomiting. Certain chemotherapy medications cause these effects more than others.

Olanzapine helps reverse this process. It works by blocking multiple chemicals in the brain, including dopamine, serotonin, and histamine. Olanzapine can be very effective at easing CINV because of this.

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When should olanzapine be prescribed for nausea and vomiting?

Olanzapine isn’t always prescribed for CINV. You may receive it depending on the “emetic risk” of the chemotherapy you’re receiving. Emetic risk refers to how likely it is for a chemotherapy regimen to cause nausea and vomiting. This ranges from low, moderate, to high.

High emetic-risk chemotherapy is defined as chemotherapy that has been shown to cause vomiting in over 90% of people. It includes medications such as cisplatin and cyclophosphamide (Cytoxan). Moderate emetic-risk chemotherapy has been shown to cause vomiting in 30% to 90% of people who receive it and includes medications such as doxorubicin (Adriamycin) and carboplatin (Paraplatin).

Olanzapine is often recommended for people who are receiving moderate or high emetic-risk chemotherapy regimens. It’s not typically used by itself, though. It’s used in combination with other antiemetic medications.

What is olanzapine normally used for?

Olanzapine is an atypical antipsychotic medication that’s FDA approved to treat schizophrenia and bipolar 1 disorder. 

For these olanzapine uses, the medication is typically prescribed at a higher dosage than what is recommended for nausea and vomiting prevention. It’s also taken every day for a longer period of time.

What is the typical olanzapine dosage for nausea and vomiting?

The typical olanzapine dosage for CINV prevention is based on the emetic risk of the chemotherapy you’re receiving. They range from:

• High emetic-risk chemotherapy: The recommended olanzapine dose is 1 tablet (5 mg to 10 mg) daily on days 1 through 4 of chemotherapy. This means after you receive your first day of chemotherapy, you’ll continue taking olanzapine for 3 more days to help prevent delayed nausea and vomiting.

• Moderate emetic-risk chemotherapy: The recommended olanzapine dose is 5 mg to 10 mg daily on days 1 through 3 of chemotherapy.

• Low and minimal emetic-risk chemotherapy: Olanzapine is not usually used in this case. The risk of nausea and vomiting is fairly low. There are other antiemetics, such as dexamethasone (Decadron) and ondansetron (Zofran), that can help treat nausea and vomiting instead.

Another situation that olanzapine can be used for is breakthrough nausea and vomiting. This is a form of nausea that develops despite being treated with other antiemetics within the past 5 days. In this case, the typical olanzapine dosage is 5 mg to 10 mg daily.

What other antiemetics are normally combined with olanzapine?

Olanzapine is usually combined with other medications for the prevention of CINV. This allows for multiple medications to combine forces to combat nausea and vomiting from different angles. 

For high emetic-risk chemotherapy, olanzapine is combined with three medications: 

• An NK1 receptor antagonist, such as fosaprepitant (Emend) or aprepitant (Cinvanti)

• A serotonin receptor antagonist, such as palonosetron (Aloxi) or ondansetron (Zofran)

• A corticosteroid, such as dexamethasone

For moderate emetic-risk chemotherapy, olanzapine is often combined with two medications, such as palonosetron and dexamethasone.

What are the side effects of taking olanzapine for nausea and vomiting?

Like with all medications, side effects can happen while taking olanzapine. Thankfully, at lower doses — like those used for prevention of CINV — side effects tend to be relatively mild.

The most common olanzapine side effects to keep in mind are drowsiness and dizziness. Drowsiness is typically the worst on the second day of taking olanzapine, but it should improve within a few days. Other potential side effects include dry mouth, constipation, and low blood pressure when sitting or standing up from lying down.

If you experience excessive drowsiness or sedation from taking olanzapine 10 mg, let your oncologist know. They may recommend lowering your olanzapine dose to 5 mg. This lower dose has been shown to lower the risk of nausea and vomiting without causing as much drowsiness. If 5 mg of olanzapine still causes too much drowsiness, your healthcare team may recommend dropping your dose down to as low as 2.5 mg.

More serious side effects are also possible, but less common. Olanzapine may raise the risk of death among older adults who have a history of dementia. If this applies to you or a family member, your healthcare team will likely recommend an alternative antiemetic medication.

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Written by:

Sonja Jacobsen, PharmD, BCPS, BCOP

Sonja Jacobsen, PharmD, BCPS, BCOP,  is a clinical oncology pharmacy specialist currently practicing in Seattle. She has been practicing as a pharmacist since 2015 and is licensed to practice in Washington state and North Carolina.

Edited 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.

Reviewed by:

Vanessa Carranza, PharmD

Vanessa Carranza, PharmD, is a pharmacist who has dedicated her career to the advancement of medical education for healthcare providers, patients, and caregivers, most notably in the oncology space.

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