Antiemetics are drugs used to relieve symptoms of nausea and vomiting. These drugs work by counteracting the neurotransmitter receptors that are involved in the physical process of these symptoms. Neurotransmitters are chemical substances that transmit nerve impulses, and receptors are cells or groups of cells that receive stimuli.
Because the pathways that control and stimulate these bodily reactions are complex, the effectiveness of the various types of drugs differs depending on the patient and the source of the discomfort. In addition, few studies exist that demonstrate the effectiveness of using particular antiemetics to treat specific conditions. As a result, most physicians rely on their own observations of a drug’s effectiveness when deciding which antiemetic is best for treating a certain condition.
Certain antiemetics are commonly prescribed for nausea and vomiting triggered by specific illnesses or circumstances. For example, the drug bismuth subsalicylate may be used if flu is the source of discomfort whereas antihistamines such as dimenhydrinate or meclizine hydrochloride may be used when the symptoms result from motion sickness. The serotonin 5-HT3 receptor agonist (ondansetron) may be used to treat cyclic vomiting syndrome.
The dopamine antagonist prochlorperazine is effective in treating nausea and vomiting due to medications for general surgery, cancer chemotherapy and radiation therapy. The American Society of Clinical Oncology recently issued guidelines recommending that antiemetics be used prior to and after chemotherapy and radiation treatments to prevent nausea and vomiting commonly associated with these treatments.
Antiemetics (e.g., promethazine, ondansetron) can also be prescribed for conditions such as morning sickness (nausea and/or vomiting experienced by many women during pregnancy).
Different antiemetics work in varying ways. For example, bismuth subsalicylate coats the stomach lining whereas antihistamines prevent the inner ear from fully sensing motion, thus blocking messages to the part of the brain that triggers nausea and vomiting.
Several different types of medications are used as antiemetics. They are available in tablet, capsule, syrup, suppository (inserted into the body through a cavity) and injection form. Commonly prescribed antiemetics include:
Type Generic Name Brand Name(s)
Pepto Bismol, Kaopectate, Bismatrol
Calm-X, Dimetabs, Dramamine, Gravol, Hydrate
Antivert, Bonine, Dizmiss, Meni-D, Ru-Vert-M
Phenergan, Promethegan, Promacot
Maxidex, Decadron, Dexone
Neurokinin receptor angonist
Serotonin 5-HT3 receptor antagonist
Alprazolam Intensol, Xanax
- Side effects
Potential side effects of antiemetics
The side effects that a person may experience depend largely on the type of antiemetic taken. In addition, not all patients will experience side effects. Less serious side effects include:
- Bismuth subsalicylate: Darkish tongue or grayish-black stools
- Antihistamines: Drowsiness, fatigue and dry mouth
- Dopamine agonists: Dry mouth, constipation, drowsiness, ringing in the ears and insomnia
- Neurokinin receptor angonists: Decreased urination, dry mouth, heartburn and hiccups
- Serotonin 5-HT3 receptor antagonists: Headache, fatigue, diarrhea, rash and constipation
- Benzodiazepine sedatives: Marked drowsiness, impaired motor function and gastrointestinal discomfort that may result in constipation, diarrhea, vomiting and changes in appetite
- Corticosteroids: Indigestion, acne, skin flushing, increased appetite and thirst
Patients should consult a physician if they experience gastrointestinal effects such as severe constipation, diarrhea or nausea and vomiting. Psychological symptoms such as depression, confusion, anxiety, excitation and hallucinations also require medical attention. Other side effects that should be reported to a physician include:
- Rapid heartbeat
- Loss of appetite
- Loss of hearing
- Difficulty speaking or slurred speech
- Dizziness or lightheadedness
- Severe drowsiness
- Fast or deep breathing
- Severe or continuing headache
- Increased sweating
- Increased thirst
- Muscle spasms, particularly in the face, neck and back
- Muscle weakness
- Ringing or buzzing in the ears
- Trembling or tremor
- Uncontrollable flapping movements of the hands or other movements
- Vision problems
- Dry mucous membranes
- Fine, worm-like tongue movements
- Yellowing of the skin or eyes
Drug or other interactions
Patients should consult their physicians before taking any additional prescriptions, over-the-counter medications, nutritional supplements or herbal medications.
Patients may find that the following medications interact poorly with bismuth subsalicylate:
- Salicylates, including aspirin
- Diabetes medications
- Anticoagulants (drugs that help prevent blood from clotting)
- Antibiotics, such as tetracyclines
Patients who are taking antihistamines should avoid alcohol, as this may increase drowsiness. Other drugs that may interact poorly with antihistamines include:
- Antibiotics, such as erythromycin.
- Anticholinergics. Drugs used to treat abdominal and stomach spasms, and cramps.
- Monoamine oxidase (MAO) inhibitors. Medications used to treat depression.
- Central nervous system depressants. Used to treat a variety of disorders.
- Antifungals, such as ketoconazole.
Medications that may interact poorly with dopamine agonists include:
- Cancer chemotherapy drugs
- Sedatives, sleeping pills or tranquilizers
- Anti-anxiety medications
- Antiseizure medications
- Drugs to treat irritable bowel syndrome, Parkinson's disease, ulcers or urinary problems
- Drugs to treat Parkinson's disease
- Muscle relaxants
- Narcotics (pain medication)
- Sleeping pills
Medications that may interact poorly with neurokinin receptor agonists include:
- Anti-anxiety medications
- Anticoagulants (help prevent the formation of blood clots)
- Chemotherapy drugs
- Oral contraceptives
Medications that may interact poorly with benzodiazepine include:
- Central nervous system (CNS) depressants
- Antifungal drugs
Medications that may interact poorly with corticosteroids include:
- Diuretics (water pills)
- Heart medications
- Cyclosporine (used to treat rheumatoid arthritis and prevent transplanted organ rejection)
- Antidiabetic agents or insulin (used to treat Diabetes)
- Medicines containing potassium (used to treat high blood pressure)
- Medicines containing sodium
- Licorice (candy made from the licorice plant’s root)
- Antacids (counteract stomach acidity)
- Anticonvulsants (used to treat seizures)
- Phenylbutazone (used to treat fever, pain and inflammation)
- Aminoglutethimide (used to treat some kinds of tumors)
- Griseofulvin (used to treat skin infections)
- Ephedrine (used to treat asthma and other conditions)
- Ritodrine (used to stop premature labor)
- Rifampin (used to treat tuberculosis)
- Barbiturates (group of drugs used as sedatives)
- Mitotane (used to treat certain cancers)
- Amphotericin B by injection (used to treat fungal infections)
- How to use
Pregnancy use issues
Women who are pregnant, thinking of becoming pregnant or breastfeeding should not use antiemetics without first consulting a physician. These medications are sometimes prescribed for cases of morning sickness (nausea or vomiting experienced by many women during pregnancy).The potential risk to a fetus or newborn posed by an antiemetic depends on the type of antemetic being used. A physician should be consulted before using any antiemetic.
Child use issues
Parents should not give any antiemetic to children without first consulting a physician. The appropriateness of giving antiemetics to children depends on the type of medication used and the age of the child. For example, children who take promethazine may experience breathing that slows or stops, possibly resulting in death. This drug should not be used by babies or children who are younger than 2 years old.
Elderly use issues
Elderly patients should consult their physician before taking antiemetics. Some of these medications may be more likely to cause side effects in elderly patients than in younger adults.
Questions for your doctorPatients may wish to ask their doctor the following antiemetic-related questions:
- What type of antiemetic do you recommend to treat my symptoms?
- Why are you recommending this particular type of antiemetic for me?
- Is the medication you recommend for me prescription or over-the-counter? If prescription, is there a generic version available and would that be an alternative for me?
- What are the potential side effects of the medication you are recommending for me?
- Which side effects, if any, should I immediately report to you?
- How long should it take for this medication to relieve my symptoms?
- What should I do if I do not notice any change in my symptoms when taking this medication?
- If this antiemetic does not work for me, what are my other options?
- Do any of the medications I am currently taking preclude use of antiemetics?
- Are there any over-the-counter medications or products I should avoid when taking this medication?