Antiemetics: Uses, common brands, and safety info

Nausea and vomiting are common symptoms that cause significant discomfort for patients. There are many possible causes for nausea and vomiting such as an infection, eating spoiled food, or motion sickness caused by traveling. Antiemetics are a class of drugs that alleviate these symptoms. Antiemetics can be taken once a patient has begun to experience symptoms, or they may be taken beforehand to prevent them. 

There are a variety of antiemetics available to treat different causes of nausea and vomiting. All are effective, but many are only appropriate for certain situations. Antiemetics vary greatly in the way they work, their side effects, and their route of administration. In this article, we will review important details about antiemetics—including their properties, common brand names, and their safe use.

Other antiemetics

OTC:

• Benadryl (diphenhydramine)

• Bonine (meclizine)

• Bonine for Kids (cyclizine)

• Dramamine (dimenhydrinate)

• Emetrol (orthophosphoric acid)

• Pyridoxine (also known as vitamin B6)

• Bismuth subsalicylate (Pepto-Bismol)

Prescription only:

• Inapsine (droperidol) 

• Cesamet (Nabilone)

• Lorazepam 

• Syndros (dronabinol oral solution) 

• Medrol (methylprednisolone)

• Antivert (meclizine)  

What are antiemetics?

Antiemetics are drugs used to treat or prevent nausea and vomiting (emesis). Antiemetics come in many forms including tablets or capsules, liquids, rectal suppositories, transdermal patches, and intramuscular or intravenous injections. Some antiemetic drugs are available over the counter while others require a prescription.

How do antiemetics work?

There are various biological processes that can lead to nausea and vomiting. Most involve the brain and the gut. Antiemetics work at both sites. Some work more at the central nervous system, others work more on visceral nerves that control the activity of the gastrointestinal (GI) tract. Ultimately, the central nervous system and the GI tract are constantly communicating, so affecting one will also influence the other. The specific pathways of communication between the two are endless, which accounts for the many ways of treating nausea and vomiting.

Since different types of antiemetics are more effective for certain types of nausea, a healthcare provider will assess the specific causes of nausea before choosing an antiemetic regimen.

What are antiemetics used for?

Antiemetics treat or prevent nausea and vomiting. Common causes of nausea and vomiting include motion sickness, gastroenteritis (stomach flu), pain, migraines, blockages in the gut, radiation therapy, opioid medications, chemotherapy, and anesthesia during surgery. Antiemetics also treat nausea associated with pregnancy, such as morning sickness or hyperemesis gravidarum.

Types of antiemetics

H-1 antihistamines

H-1 antihistamines include most over-the-counter antiemetics such as Antivert (meclizine), Bonine (meclizine), Bonine for Kids (cyclizine), and Dramamine (dimenhydrinate). This class also includes prescription drugs like Promethegan (promethazine) and Diclegis (doxylamine-pyridoxine). These antiemetics work by inhibiting parts of the inner ear and brain that process motion, sense of space, and balance. This class is most effective at treating motion sickness.

Anticholinergics

Anticholinergic drugs prevent or treat nausea in a similar way to antihistamines. They reduce the activity of a neurotransmitter called acetylcholine, which travels from the inner ear to the vomiting center of the brain. The most common example is Transderm Scop (scopolamine), a patch placed on the skin behind the ear. Many other antiemetics, including all the antihistamines listed above, also exhibit some degree of anticholinergic activity. Scopolamine is mainly used to treat motion sickness but can be used for other types of nausea and vomiting.

Neurokinin-1 inhibitors

Neurokinin-1 inhibitors such as Emend (aprepitant), Emend for injection (fosaprepitant), Aknyzeo (netupitant-palonosteron), and Varubi (rolapitant) are used to treat postoperative nausea and vomiting (PONV) and chemotherapy-induced nausea and vomiting (CINV) in adults and children. They are particularly useful for treating “delayed” nausea after chemotherapy. Neurokinin-1 inhibitors are a relatively new class of antiemetic drugs that inhibit a neurotransmitter called “Substance P.” This neurotransmitter is increased as a side effect of chemotherapy, and acts in the vomiting center of the brain. 

Cannabinoids

Cannabinoid antiemetics include Marinol (dronabinol capsules), Syndros (dronabinol oral solution), and Cesamet (Nabilone). They are controlled substances and are FDA approved for chemotherapy-induced nausea and vomiting in adults who have not responded sufficiently to other antiemetics such as serotonin receptor antagonists, dopamine receptor antagonists, and steroids. Cannabinoids activate CB1 and CB2 receptors in the regions of the brain and gut that are involved in the control of nausea and vomiting.

Serotonin receptor antagonists

Serotonin receptor antagonists (or 5-HT3 receptor antagonists) include commonly used drugs such as Zofran (ondansetron), Anzemet (dolasetron), Aloxi (palonosetron), and granisetron. Serotonin receptor antagonists reduce the activity of the neurotransmitter serotonin at various locations in the nervous system, including the chemoreceptor trigger zone (CTZ) in the brain and at vagal nerve terminals in the gut. They are FDA-approved for use in adults to prevent nausea and vomiting associated with chemotherapy, radiation therapy, and surgery. They are also FDA-approved for preventing chemotherapy-induced or postoperative nausea and vomiting in children. Anzemet (dolasetron) is FDA-approved for the treatment of postoperative nausea and vomiting.

Dopamine receptor antagonists

Dopamine receptor antagonists include the brand name antiemetics Compazine (prochlorperazine), Reglan (metoclopramide), and Inapsine (droperidol). They block the neurotransmitter dopamine. Like serotonin, this neurotransmitter stimulates nausea through its effect on the chemoreceptor trigger zone and the gut. For example, dopamine slows down the activity of the intestines which can cause nausea, vomiting, and constipation. 

Corticosteroids

Corticosteroids such as dexamethasone and methylprednisolone have been used to prevent CINV since the 1980s. They are usually used in combination with other classes of antiemetics. It is not fully understood how they alleviate nausea and vomiting, although it is likely related to its ability to reduce inflammation by suppressing prostaglandins. These molecules are involved in countless biological processes, including nausea.

Most antiemetics have characteristics of more than one class. One example is promethazine; it is an H-1 antihistamine and an antipsychotic that inhibits serotonin and dopamine. Sometimes different classes of antiemetics are used in combination. For example, neurokinin-1 inhibitors are often used in combination with serotonin agonists and corticosteroids during chemotherapy.

Who can take antiemetics?

Infants, children, and adolescents

Some antiemetics are safe and effective to use in pediatric patients when used with caution. Dexamethasone has been studied and shown to be safe in children experiencing nausea related to chemotherapy. Scopolamine patches are extensively used to alleviate motion sickness and postoperative nausea and vomiting in children. Serotonin receptor antagonists such as ondansetron are safe and effective for treating nausea in children if doses are kept below a certain threshold. 

Antihistamines other than promethazine are safe options for treating nausea and children. Promethazine is contraindicated in children less than 2 years due to its side effect of respiratory depression. Dopamine receptor antagonists such as metoclopramide should generally be avoided due to side effects such as tardive dyskinesia. They should not be used in children less than 1 year and should be used with extreme caution in older children. The neurokinin-1 inhibitors aprepitant and fosaprepitant are approved for use in children greater than 6 months of age. Varubi (rolapitant) is contraindicated in pediatric patients less than 2 years of age due to irreversible damage to sexual development, as demonstrated in rats. 

Adults 

Antiemetic drugs are safe to be used in adults. The most common side effects are the result of anticholinergic properties and include dry mouth, decreased urination, constipation, drowsiness, dizziness, and fatigue. Some patients may experience less tolerable side effects depending on their dose, the type of antiemetic, and other underlying health conditions. It is important to consult a healthcare provider about troublesome side effects so that treatment can be adjusted accordingly.  

Seniors

Most antiemetic drugs can be safely used in the elderly population, although side effects may be more pronounced as the body clears drugs less quickly with older age. The anticholinergic side effects of many antiemetics should be monitored closely, since orthostatic hypotension, sedation, and fatigue may increase the risk of falls. Antiemetics that double as antipsychotics, such as prochlorperazine, may contribute to cognitive impairment, sedation, and confusion, which also increases risk of falls. Additionally, they carry a black box warning about the precipitation of psychosis in demented elderly patients, and an increased risk of death. Most antiemetics can be safely used in the elderly when initiated at a low dose and with careful monitoring. 

Are antiemetics safe?

Antiemetics recalls

Listed below are recent recalls involving antiemetic drugs. This list may not be all-inclusive. Your pharmacist can help with questions or concerns related to recalled medications.

• Wilshire Pharmaceuticals, Inc. voluntary recall of affected bottles of Meclizine 12.5 mg and 25 mg tablets due failed dissolution specifications (February 4, 2021).

• Infusion Options, Inc. voluntary recall of affected vials of ondansetron 8 mg / 50 mL solution for injection, due to lack of assurance of sterility (June 12, 2019).

• RXQ Compounding voluntary recall of affected vials of ondansetron 2 mg / mL solution for injection, due to lack of assurance of sterility (August 8, 2019).

• Axia Pharmaceutical voluntary recall of affected vials of dexamethasone LA 16 mg / 10 mL injectable suspension, due to lack of assurance of sterility (January 15, 2020).

• Fresenius Kabi USA, LLC voluntary recall of affected vials of fosaprepitant 150 mg / 10 mL solution for injection, due to label error on declared strength of the excipient ingredient edetate disodium (EDTA) (July 13, 2020).

• Glenmark Pharmaceuticals Inc., voluntary recall of affected packages of aprepitant 40 mg capsules, due to customer reports of missing capsules in the blister pack (September 12, 2019).

Antiemetics restrictions

Certain antiemetics classified as dopamine receptor antagonists should not be used in patients with an intestinal obstruction or any condition where stimulation of gastrointestinal motility might be harmful. Examples of such conditions may include gastrointestinal bleeding or perforation.

Dopamine receptor antagonists should not be used in patients with prolactin-dependent tumors, as these medications can increase prolactin levels. 

Dopamine receptor antagonists should not be used in patients with Parkinson’s disease as these medications may worsen symptoms.

Dopamine receptor antagonists such as metoclopramide may cause irreversible tardive dyskinesia with repeated and prolonged use. For this reason, it is not recommended that metoclopramide be used for more than 12 weeks.

Anticholinergic antiemetics should not be used in patients with heart failure, tachyarrhythmias, urinary retention, benign prostatic hyperplasia (BPH), glaucoma, hypotension, or pyloric stenosis.

Antiemetics classified as serotonin receptor antagonists should be used with extreme caution in patients with prolonged QTc, or in patients with a history of serotonin syndrome.

Antiemetics classified as corticosteroids (dexamethasone, methylprednisolone) should not be used in patients with systemic fungal infections.

Antiemetics of any kind should be avoided if there is a known hypersensitivity to any of its components.

Patients with severe liver or kidney disease should be monitored closely while taking certain antiemetics. Their dosages may need to be adjusted to avoid increased side effects.

Can you take antiemetics while pregnant or breastfeeding?

Several antiemetics, such as metoclopramide, doxylamine, and diphenhydramine, are effective for nausea during pregnancy and present no risk for birth defects. Most antiemetics are generally safe to use while pregnant or breastfeeding. Exceptions include neurokinin-1 inhibitors, due to lack of safety data. There may be risk for birth defects or harm to the nursing infant based on limited studies in humans and animals.

Are antiemetics controlled substances?

A few antiemetic drugs are classified as controlled substances by the DEA due to their potential for abuse and misuse. Cesamet (nabilone) and Syndros (dronabinol oral solution) are listed as schedule-II controlled substances. Drugs in this category are the most highly regulated of all prescription drugs. Marinol (dronabinol) is a schedule-III controlled substance. The scheduling system, and specific drugs assigned to a schedule, can differ among states. Each state may add, delete, or change the schedule of a drug within its premises based on the state Controlled Substance Acts.

Common antiemetics side effects

Antiemetic drugs vary in their side effects due to their different mechanisms of action. Many antiemetics can cause:

• Dry mouth

• Decreased urination

• Constipation

• Sedation (drowsiness)

• Fatigue

Below are some additional adverse effects common to individual classes of antiemetics:

Dopamine receptor antagonists:

• Akathisia

• Dystonia

• Parkinsonian symptoms

• Changes in blood pressure

• Insomnia

• Headache

• Restlessness

• Diarrhea

Neurokinin-1 inhibitors:

• Diarrhea

• Loss of appetite

• Headache

• Fever

• Stomach upset

Serotonin receptor antagonists:

• QTc prolongation

• Headache

• Diarrhea

• Fever

• Itching

• Agitation

Corticosteroids:

• Increased appetite

• Fluid retention

• Headache

• Increased blood pressure

• Insomnia

Cannabinoids:

• Dizziness

• Anxiety

• Confusion

• Hallucinations

How much do antiemetics cost?

Most antiemetics are available as a generic at a much lower cost than their brand-name alternatives. For example, the average price of the generic drug ondansetron is around $52 for 10 tablets, while the price for the brand name (Zofran) is more than $270. With a SingleCare coupon, the generic ondansetron can cost as little as $6.67 for the same number of tablets. Many prescription and OTC antiemetics are available for less than $50 and cost significantly less with a SingleCare coupon. For example, a three-month supply of meclizine cost as little as $4.06 with a SingleCare coupon.

Commercial insurance plans have different limitations or conditions for their coverage of antiemetics. Most antiemetics are covered by Medicare. Antiemetics may be covered under Medicare Part B when administered within a couple hours of chemotherapy and with certain other conditions met. Otherwise, most antiemetics will be covered under Medicare Part D.

Before you fill your prescription, check with SingleCare to make sure you are paying the lowest possible price.