Antiemetic drugs are medicines that ease nausea or vomiting. A person might use an over-the-counter or prescription version.
The feeling of nausea results from a complex process in the body, and this is why various drugs have been designed to ease nausea in different situations.
Antiemetic drugs can help when nausea and vomiting stem from, for example:
- motion sickness
- viral or bacterial infections, such as those responsible for the stomach flu
- the effects of surgery
- other medications, such as chemotherapy
These medications work by blocking chemical messengers called neurotransmitters, which send information about nausea to the brain. Blocking their signals can keep a person from feeling nauseous and vomiting.
Below, we look at various types of antiemetics, their uses, and their possible side effects.
Different antiemetic drugs have been designed to address nausea stemming from different causes. Below are examples of these medications, grouped by their purposes.
Antiemetics for motion sickness
Medicines called antihistamines may help prevent nausea and vomiting caused by motion sickness, and some are available over the counter.
These medications desensitize the inner ear to the motion of the head. The inner ear plays an important role in balance, and it is sensitive to the movements caused by sitting in a moving car or a boat, for example.
Antihistamines that combat nausea caused by motion sickness include:
- diphenhydramine (Benadryl)
- meclizine (Bonine)
- promethazine (Phenergan)
- dimenhydrinate (Dramamine, Gravol)
Each can cause side effects, and it is important to speak with a doctor before trying one.
Antiemetics for the stomach flu
Some people with gastroenteritis, or the stomach flu, need antiemetics to relieve their symptoms.
While vomiting can help get rid of any stomach irritants, excessive vomiting can damage the digestive tract. Nausea may also prevent a person from eating and drinking enough to take in necessary nutrients and stay hydrated.
The over-the-counter medications below can ease the nausea as the body fights off the infection:
- sodium citrate, dextrose, and fructose (Nauzene)
- orthophosphoric acid, fructose, and glucose (Emetrol)
- bismuth subsalicylate (Pepto Bismol)
Antiemetics during pregnancy
Antiemetic drugs can also help relieve morning sickness.
Doctors usually only prescribe them if nausea and vomiting are severe, interfering with daily life. This can be the case, for example, if the person has hyperemesis gravidarum, a lasting, serious form of morning sickness.
A few medications can help and are safe during pregnancy, and it is important for the doctor to carefully describe the possible side effects of the drug that they recommend.
Some antiemetics for morning sickness include:
If the symptoms do not respond well, the doctor may prescribe metoclopramide (Reglan).
It is important to note that using cannabis during pregnancy is not safe and may affect the developing fetus.
Antiemetics after surgery
People who undergo anesthesia for surgery frequently experience nausea and vomiting afterward.
Antiemetics that a doctor may prescribe after surgery include:
- dexamethasone (Decadron)
- droperidol (Inapsine)
- granisetron (Kytril)
- metoclopramide (Reglan)
- ondansetron (Zofran)
Antiemetics for cancer and chemotherapy
Chemotherapy often causes nausea and vomiting. A doctor may prescribe an antiemetic before and after chemo to help prevent these side effects and improve the quality of life.
Different types of drugs can help, including serotonin and dopamine receptor blockers, NK1 receptor blockers, and corticosteroids.
Some antiemetics that people take to combat nausea from chemotherapy include:
- aprepitant (Emend)
- dexamethasone (DexPak)
- dolasetron (Anzemet)
- granisetron (Kytril)
- ondansetron (Zofran)
- palonosetron (Aloxi)
- prochlorperazine (Compazine)
- rolapitant (Varubi)
If these treatments are ineffective, cannabinoids from medical marijuana or other prescription drugs, such as dronabinol (Marinol), may help. They can cause side effects, however.
Each antiemetic drug can cause specific side effects. It is crucial to read each drug’s pamphlet carefully or speak with a pharmacist about the risks.
When deciding upon a treatment to prescribe, it is important for a doctor to understand which side effects the person is more prone to experience.
The following are common side effects of different types of antiemetics:
- antihistamines: sleepiness, dry mouth, and dry nasal passages
- bismuth-subsalicylate: blackish stools and changes in tongue color
- cannabinoids: an altered state of perception and dizziness
- corticosteroids: indigestion, increased appetite or thirst, and acne
- dopamine receptor blockers: fatigue, constipation, ringing in the ears, dry mouth, restlessness, and muscle spasms
- NK1 receptor blockers: dry mouth, reduced urine volume, and heartburn
- serotonin receptor blockers: fatigue, dry mouth, and constipation
Antiemetics can help people live without nausea and vomiting, but they can also cause side effects and interactions, some of which can be severe.
Alert a doctor if any of the following occur:
- muscle weakness, spasms, or convulsions
- changes in heartbeat, such as palpitations or a rapid heartbeat
- hearing loss
- worsening of nausea or vomiting
- slurred speech
- psychological problems, such as hallucinations or confusion
- drowsiness that interferes with daily life
It is important to discuss the options with a doctor before trying any antiemetic — especially for people who take other medications. For instance, anyone who takes a sleep aid or muscle relaxant should consult a doctor before taking an antihistamine for nausea and vomiting.
Also, taking an antiemetic and another medication that can cause similar side effects may result in worsened unwanted effects.
Medications with similar side effects include:
Some natural options exist for people who prefer to avoid drugs.
Ginger is a traditional remedy for nausea and an upset stomach. The findings of a review from 2015, for example, confirm its effectiveness, though the researchers highlight the need for more research.
There is not enough evidence to say whether it can ease nausea caused by motion sickness or the effects of anesthesia, however.
Meanwhile, there is some evidence that peppermint, lavender, and lemon essential oils may help with nausea.
Antiemetics are drugs that combat nausea and vomiting, with different drugs designed to address specific causes of nausea.
Anyone who is unsure whether an antiemetic may be helpful should speak with a healthcare provider or pharmacist. This is crucial for people who take other types of medication.