What Are Antiemetic Drugs? A GoodRx Guide to Zofran, Promethazine, and More
Key takeaways:
Nausea and vomiting happen for many different reasons. It’s important to try to find out what’s causing these symptoms to find the best medication to treat them.
“Antiemetic” is a medical term that means “anti-vomiting.” So antiemetic drugs are medications that prevent or treat nausea and vomiting.
There are several different types of antiemetic drugs, all of which affect different areas of the body to control nausea and vomiting in unique ways. Serotonin receptor antagonists, such as ondansetron (Zofran), and antihistamines, such as promethazine, are common examples. Talk to your healthcare provider about the best antiemetic drug options for you.
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Table of contents
Nausea and vomiting are no fun. As uncomfortable as they are, these symptoms can be your body’s attempt to remove something harmful from the digestive tract. But you still may wonder how you can get some relief.
Antiemetic drugs are medications that can prevent or treat nausea and vomiting. There are many types of antiemetic drugs available. And that’s because there are many possible ways the body can trigger nausea and vomiting.
Some common antiemetic drugs, such as dimenhydrinate (Dramamine), are available over the counter (OTC). Others require a prescription. In this article, we’ll discuss the different types of antiemetic drugs and how they work.
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How do antiemetic medications work?
Antiemetic drugs work by blocking certain signals in your brain that make you feel nauseated.
We tend to think of nausea and vomiting as stomach-related problems. But it’s actually the brain that triggers these uncomfortable symptoms. Different chemical messengers enter or affect the “vomiting center” of the brain. This causes you to feel nauseated or throw up.
Examples of these chemical messengers include:
Histamine
Dopamine
Serotonin
Neurokinins (NKs)
Acetylcholine
Antiemetic drugs work by blocking one or more of these chemical messengers. They stop the chemicals from attaching to their target locations, which are called receptors (chemical binding sites). The receptors involved vary depending on what’s causing the nausea.
What are the six different classes of antiemetic drugs?
There are six different classes of FDA-approved antiemetic drugs:
Neurokinin-1 (NK1) receptor antagonists
Serotonin receptor antagonists
Dopamine receptor antagonists
Cannabinoids
Antihistamines
Anticholinergics
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Not all medications in these classes are approved to treat nausea and vomiting. But some experts still recommend them as treatment options, or for “off-label” use. Some healthcare providers also prescribe corticosteroid medications off label for nausea and vomiting. These medications can be effective options, especially for people whose symptoms are caused by chemotherapy.
As we’ll discuss below, antiemetic drugs can be used to treat or prevent nausea and vomiting from a variety of causes. And some classes work better for certain causes than others. So if you’re taking an antiemetic drug and it’s not working, it’s best to contact your healthcare provider and ask about a potential alternative.
1. NK1 receptor antagonists
NK1 receptor antagonists are antiemetics that work by blocking NK1 receptors in the brain. These medications are most often used to treat nausea and vomiting caused by cancer treatments. They can also help manage nausea from surgery.
Normally, NK1 receptors are triggered by a chemical called substance P (a type of NK). Substance P plays a role in how we perceive pain. But when it attaches to NK1 receptors, it can cause nausea and vomiting.
Chemotherapy can cause the body to release a lot of chemical messengers, including substance P. Because NK1 receptor antagonists block substance P from binding to receptors, they tend to be effective for chemotherapy-induced nausea and vomiting (CINV).
NK1 receptor antagonists are available as oral pills and IV injections. Examples of antiemetics in the NK1 receptor antagonist class include:
Aprepitant (Emend, Aponvie, Cinvanti)
Fosaprepitant (Emend, Focinvez)
Rolapitant (Varubi)
2. Serotonin receptor antagonists
Serotonin receptor antagonists also help manage nausea and vomiting. This is because a small area of the brain called the chemoreceptor trigger zone (CTZ) has serotonin receptors. The nerves around the digestive tract have these receptors, too. These receptors trigger nausea and vomiting when serotonin attaches to them. Serotonin receptor antagonists block serotonin from attaching and help stop this effect.
Your body naturally releases serotonin after receiving chemotherapy. So, alongside NK1 receptor antagonists, serotonin receptor antagonists also help manage CINV. But these medications are effective for many other types of nausea and vomiting, too. Medications in this class can also be taken after surgery and during pregnancy to help with nausea and vomiting.
Common examples of serotonin receptor antagonists are:
Ondansetron (Zofran)
Dolasetron (Anzemet)
Granisetron (Sancuso)
Serotonin receptor antagonists are available in many different dosage forms, including oral liquids, tablets, and IV injections.
3. Dopamine receptor antagonists
Several antiemetic drugs are dopamine receptor antagonists. Some of these medications are also considered antipsychotics, which treat certain mental health conditions. But different doses are prescribed based on whether the medications are being used to treat nausea and vomiting or mental health issues.
Dopamine receptor antagonists block dopamine from attaching to receptors in the CTZ. They are useful for many types of nausea and vomiting, including CINV. So they’re actually some of the most commonly prescribed antiemetic drugs.
Examples of antiemetics in the dopamine receptor antagonist class are chlorpromazine and prochlorperazine. Medications in this class can be administered as tablets, oral concentrates, and IV injections. Suppositories are available, too.
4. Cannabinoids
Cannabinoids are medications that include lab-made versions of compounds found in cannabis, such as tetrahydrocannabinol (THC). Cannabinoids manage nausea and vomiting by activating cannabinoid receptors in the gut. This helps slow down the motion of the digestive tract.
Cannabinoids haven’t been well studied for many types of nausea and vomiting. However, they are known to be effective for CINV. More research needs to be done to see if they’re helpful for other types.
Cannabinoids that are approved to treat CINV are dronabinol (Marinol, Syndros) and nabilone (Cesamet). They’re available as capsules and a liquid solution.
5. Antihistamines
Antihistamines are best known for treating allergies. But some antihistamines can be helpful for nausea and vomiting, too. These antiemetic drugs block histamine from attaching to receptors in the vomiting center of the brain. They also block histamine from attaching to other receptors throughout the central nervous system (the brain and spinal cord).
Since antihistamines affect the central nervous system, they’re great at helping with nausea and vomiting from vertigo, inner ear infections, and motion sickness. They’re also some of the more preferred medications for treating morning sickness.
Examples of antihistamines medications include:
Dimenhydrinate
Doxylamine (Unisom)
Meclizine (Antivert, Bonine)
Most OTC antihistamines come as oral tablets. But some prescription-only antihistamines are also available as syrups, suppositories, and IV injections.
6. Anticholinergics
Anticholinergics have a wide variety of uses. They block a chemical called acetylcholine from attaching to receptors throughout the body. But the way they help prevent nausea and vomiting isn’t fully understood.
Anticholinergics are most helpful for preventing nausea and vomiting related to motion sickness. The most common anticholinergic used for nausea and vomiting is scopolamine (Transderm Scop). It comes as a skin patch that’s placed behind the ear.
What conditions can antiemetics be used for?
There are many possible explanations for nausea and vomiting. Some common causes of nausea and vomiting include:
Certain medications, especially chemotherapy
Morning sickness
Viral or bacterial infections
Stomach conditions, such as gastroesophageal reflux disease (GERD)
What are the side effects of antiemetic medications?
Antiemetic medications are generally well tolerated. Some common side effects of antiemetics include:
Fatigue
Headache
Dizziness
Make sure to talk with your healthcare provider before starting treatment with an antiemetic medication. They can tell you more about what to expect.
Which antiemetic drugs are most effective?
As mentioned earlier, some antiemetic drugs work better in certain situations than others. Below, we’ll review a few causes of nausea and vomiting and which antiemetic drugs typically work best for each.
Chemotherapy
Many people require a combination of antiemetic drugs to treat CINV, since one isn’t always enough. However, the severity of nausea and vomiting depends on the chemotherapy medications that are being prescribed.
Some of the most effective medications for CINV are NK1 receptor antagonists, serotonin receptor antagonists, and dopamine receptor antagonists. As mentioned earlier, corticosteroids, such as dexamethasone, are also commonly prescribed for this purpose.
Cancer specialists are very well versed in antiemetic drugs. Your specialist will make you sure you receive the most appropriate medication(s) for your situation.
Food poisoning
Food poisoning happens as a result of a viral or bacterial infection in your digestive tract. It usually occurs after eating food that isn’t cooked, prepared, or stored properly. Symptoms can include nausea, diarrhea, and abdominal cramps.
The most effective antiemetic drugs for food poisoning are usually dopamine receptor antagonists and serotonin receptor antagonists. Of these two classes, only serotonin receptor antagonists are recommended for children. Ondansetron for children is usually a first-choice option in these cases.
Motion sickness and inner ear infections
Inner ear infections can sometimes cause symptoms that are similar to those of motion sickness. When nausea or vomiting is due to an inner ear infection or motion sickness, the best antiemetic drugs are antihistamines, anticholinergics, and dopamine receptor antagonists.
Morning sickness
There are several antiemetic drugs that are safe and effective for people with morning sickness. Doxylamine, an antihistamine, is a first-choice option on its own and in combination with vitamin B6 (pyridoxine).
Other OTC antihistamines are also safe and effective at treating nausea and vomiting related to morning sickness. Dopamine receptor antagonists and serotonin receptor antagonists can be used for morning sickness, as well. But these are considered second-choice options.
Migraines
Antiemetic drugs aren’t considered first-choice options for treating migraine symptoms. These medications are usually only recommended when other migraine medications aren’t working well enough. When they’re needed, dopamine receptor antagonists are generally the most effective option for treating nausea and vomiting related to migraines.
How to save on antiemetic drugs
There are many ways to save on antiemetic drugs. GoodRx can help you navigate your options, which may include GoodRx discounts and patient assistance programs. You may be able to find nausea medication prices for as low as $6 with a free GoodRx coupon.
The bottom line
Antiemetic drugs, such as ondansetron (Zofran) and promethazine, are medications that can manage nausea and vomiting. They work for nausea and vomiting related to a variety of causes. But some antiemetic drugs work better in certain instances than others. For this reason, it’s best to ask your healthcare provider which antiemetic drug would be best to treat your nausea and vomiting.
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References
Athavale, A., et al. (2020). Antiemetic drugs: What to prescribe and when. Australian Prescriber.
Bhakta, A., et al. (2017). Causes and treatment of nausea and vomiting. Prescriber.
Hartman, S., et al. (2019). Gastroenteritis in children. American Family Physician.
Hauser, J. M., et al. (2022). Antiemetic medications. StatPearls.
Ibrahim, M. A., et al. (2023). Antiemetic neurokinin-1 receptor blockers. StatPearls.
MacDougall, M. R., et al. (2023). Physiology, chemoreceptor trigger zone. StatPearls.
Mayans, L., et al. (2018). Acute migraine headache: Treatment strategies. American Family Physician.
MedlinePlus. (2020). Nausea and vomiting.
Migirov, A., et al. (2022). Antiemetic antimuscarinics. StatPearls.
National Cancer Institute. (2023). Nausea and vomiting related to cancer treatment (PDQ) – Patient version.
National Comprehensive Cancer Network. (2022). NCCN guidelines for patients: Nausea and vomiting.
Okafor, D., et al. (2017). The role of neurokinin-1 (substance P) antagonists in the prevention of postoperative nausea and vomiting. Journal of Anaesthesiology Clinical Pharmacology.
Parker, L. A., et al. (2011). Regulation of nausea and vomiting by cannabinoids. British Journal of Pharmacology.
Schaefer, T. S., et al. (2023). Antiemetic histamine H1 receptor blockers. StatPearls.
Smith, H. S., et al. (2012). Dopamine receptor antagonists. Annals of Palliative Medicine.
Theriot, J., et al. (2022). Antiemetic serotonin-5-HT3 receptor blockers. StatPearls.
