Antiemetic Drugs

What are antiemetic drugs?

Antiemetic drugs are medications that help prevent and treat nausea and vomiting. “Anti-” means “against.” And “-emetic” comes from “emesis,” which is the medical term for vomiting.

There are several types (drug classes) of antiemetics. Some you can get over the counter (OTC), and others are prescriptions. There are many different causes of nausea and vomiting. So, certain types of antiemetics are more effective for specific causes.

When would I need an antiemetic drug?

Vomiting is often a protective reflex for your body — like when you’ve eaten something spoiled or have a stomach flu. But severe and/or frequent vomiting can lead to serious health issues, like:

• Bone fractures
• Dehydration
• Esophageal rupture, known as Boerhaave’s syndrome
• Loss of appetite
• Malnutrition
• Mental changes
• Tooth enamel erosion
• Reopening of surgical wounds

Because of this, healthcare providers prescribe antiemetics for certain situations to prevent and/or treat vomiting that has already started.

Preventing and treating chronic nausea and vomiting

Your provider may prescribe an antiemetic drug if you have severe and/or chronic nausea and vomiting. Examples include:

• Radiation- and chemotherapy-induced nausea and vomiting (CINV). Most people who receive chemotherapy experience nausea and/or vomiting as side effects. Radiation therapy to your brain, gastrointestinal tract or liver also often causes these side effects. Because of this, providers recommend taking antiemetics while you’re undergoing chemotherapy or radiation therapy. Excessive nausea and vomiting are especially dangerous if you have cancer.
• Pregnancy-related nausea and vomiting (morning sickness). Some providers recommend certain over-the-counter antiemetics for this. Providers also recommend OTC or prescription antiemetics for hyperemesis gravidarum (severe vomiting during pregnancy).

Always talk to your healthcare provider about when and how you should take antiemetic drugs. You may need more than one type of antiemetic, especially for CINV. If you have pregnancy-related nausea and vomiting, talk to your provider before trying an OTC medication.

Preventing short-term nausea and vomiting

Providers may recommend or prescribe antiemetics to prevent short-term nausea and vomiting that are very likely to happen.

Nausea and vomiting are common side effects of many medications, including anesthetics (anesthesia) and opioids. Providers often use these medications for procedures and surgeries. Because of this, they often give you an antiemetic drug to prevent nausea and vomiting after surgery. This is called postoperative nausea and vomiting (PONV).

Vertigo and motion sickness can cause nausea and vomiting as well. Your provider may recommend taking an antiemetic if you’re going to be in a situation that may trigger these conditions.

There may be other situations in which your provider will recommend an antiemetic.

What are the types of antiemetic drugs?

There are seven subgroups of antiemetic drugs, most of which have multiple types of medications.

Serotonin antagonists

Serotonin antagonists specifically treat nausea and vomiting. They’re common antiemetics. They include:

• Granisetron (Kytril®)
• Ondansetron (Zofran®)
• Palonosetron (Aloxi®)

These medications have approval from the U.S. Food and Drug Administration (FDA) for preventing:

• CINV and radiation therapy-induced nausea and vomiting
• PONV

Healthcare providers sometimes prescribe these medications for other conditions. This is considered an off-label, or non-FDA-approved, use of the medication.

Antihistamines

Providers mainly use histamine 1 (H1) receptor antihistamines to manage symptoms related to allergies. But some of these antihistamines have FDA approval to prevent and treat nausea and vomiting related to motion sickness and vertigo. Providers may recommend some of them off-label for pregnancy-related nausea and vomiting if other antiemetics haven’t worked.

Antiemetic antihistamines include:

• Dimenhydrinate chewable tablets (Dramamine®)
• Diphenhydramine capsules or tablets (Benadryl®)
• Doxylamine succinate with vitamin B6 — the first-line (first-choice) treatment for pregnancy-related nausea and vomiting
• Meclizine (Antivert®, Bonine®, Travel Sickness®)
• Promethazine (Phenergan®)

Diphenhydramine and dimenhydrinate can also help with preventing PONV. But they’re usually not first-line medications for it.

Glucocorticoids

Healthcare providers mainly use glucocorticoids (corticosteroids) for their anti-allergic and anti-inflammatory functions. But some also work as antiemetics.

Dexamethasone (Baycadron Elixer®, Decadron®, Zema-Pak® and others) is the main glucocorticoid that providers use for preventing CINV and PONV.

Providers may combine a glucocorticoid with other antiemetics to prevent nausea and vomiting. Unlike some other antiemetics, glucocorticoids can’t treat nausea and vomiting once they’ve started.

Anticholinergics

Anticholinergics (antimuscarinics) are medications that block the action of acetylcholine (a neurotransmitter). They help treat a variety of conditions (like urinary incontinence and COPD), but they can also help with nausea and vomiting.

Scopolamine (Maldemar®, Scopace Transderm® Scop®) is the main antiemetic anticholinergic. Providers use it to:

• Prevent PONV
• Prevent or treat nausea and vomiting related to motion sickness

Neurokinin-1 receptor antagonists

Neurokinin-1 (NK-1) receptor antagonists work by blocking neurokinin, a natural substance in your brain that causes nausea and vomiting. These medications are effective for treating CINV and PONV. They also have anti-anxiety (anxiolytic) and antidepressant effects.

Medications in this group include:

• Aprepitant (Aponvie®, Emend® and Cinvanti®)
• Fosaprepitant (Emend®and Focinvez®)
• Netupitant and palonosetron combination (Akynzeo®)
• Rolapitant (Varubi®)

Dopamine antagonists

Dopamine antagonists are medications that keep certain types of cells in your brain from activating. They’re a key type of drug for treating certain mental health conditions and symptoms, especially psychosis and schizophrenia. But some types can also help with nausea and vomiting.

Antiemetic dopamine antagonists include:

• Amisulpride (Barhemsys®)
• Chlorpromazine (Thorazine®)
• Droperidol (Inapsine®)
• Haloperidol (Haldol®)
• Metoclopramide (Reglan®, Gimoti®)
• Olanzapine (Zyprexa®, Lybalvi®, Symbyax®)
• Prochlorperazine (Compro®)

Dopamine antagonists are a possible alternative when other antiemetic drugs don’t work for CINV. These drugs are also helpful for stopping PONV.

Cannabinoids

Cannabinoids are compounds in the cannabis plant (marijuana) that bind to cannabinoid receptors found in your brain, gastrointestinal tract and immune cells.

Manufactured cannabinoids are molecules designed to mimic the effects of tetrahydrocannabinol (THC). There are currently two synthetic cannabinoids available on the pharmaceutical market for use as antiemetics:

• Dronabinol (Marinol®)
• Nabilone (Cesamet®)

They have FDA approval for the treatment of CINV if first-line antiemetics haven’t worked.

Cannabinoids are the newest type of antiemetic. Researchers are still learning and studying how they work.

What forms do antiemetic drugs come in?

Most antiemetic drugs come in more than one form. They may be:

• Oral pills, like ones you swallow or chew
• IV (intravenous) solutions
• Injections into your muscle (intramuscular)
• Skin patches (transdermal) — mainly just scopolamine (an anticholinergic)
• Rectal pills (suppositories)

What are the side effects of antiemetics?

Each type of antiemetic has different possible side effects. Your healthcare provider will go over the side effects before you start the medication. Don’t hesitate to ask questions or voice your concerns. If you develop bothersome side effects after starting an antiemetic, talk to your provider.

Some common side effects (but not all) for each type of antiemetic drug include:

• Serotonin antagonists: Headache, dizziness and constipation
• Antihistamines: Drowsiness
• Glucocorticoids: Insomnia, excitation and mood changes
• Anticholinergics: Dry mouth, vision changes and drowsiness
• NK-1 receptor antagonists: Headaches, dizziness and may cause severe allergic reactions (anaphylaxis) in some people
• Dopamine antagonists: Dizziness, headache and movement issues, like dystonia (unintentional muscle contractions) and tardive dyskinesia (involuntary body movements, often of your face and mouth)
• Cannabinoids: Vertigo, low blood pressure and dysphoria (profound sense of unease or dissatisfaction)

Can I take an antiemetic drug if I’m pregnant?

You should talk with your obstetrician-gynecologist (Ob/Gyn) or another provider if nausea and vomiting during pregnancy are causing you distress. They’ll likely recommend changes in the types of food you eat or what time you eat. If that doesn’t help, they may recommend medications.

Many studies show that certain antiemetic drugs are generally safe to use during pregnancy. But others have conflicting or limited safety information. Together, you and your provider will decide what’s best for you.

Always talk to your provider as soon as you know you’re pregnant to review your medications. In addition, always talk to your provider before starting any new medications while you’re pregnant.

What should I do if I miss a dose of an antiemetic drug?

Talk to your healthcare provider if you miss a dose of an antiemetic drug, especially if it’s to prevent possible chronic nausea and vomiting, like CINV. They’ll give you instructions on what to do.