Antiemetic drugs in adults
A number of neural pathways are implicated in nausea and vomiting, including dopaminergic, serotonergic, histaminergic, cholinergic, neurokinin and cannabinoid receptor–mediated pathwaysHeckroth, 2021. Different causes of nausea and vomiting have varying effects on these pathways.
Currently, no available antiemetic acts on all receptor sites involved in the emetic response, so no antiemetic is universally effective. Additionally, nausea and vomiting are each caused by different neural pathways and transmitters, so antiemetic drugs can have varying effects on these symptoms (eg vomiting may be reduced with little effect on nausea)Heckroth, 2021. Therefore, the choice of antiemetic is determined by the clinical situation, including the patient’s comorbidities and previous response to antiemetics.
For information about common antiemetic drugs used for nausea and vomiting in palliative care patients, see Nausea and vomiting in palliative care.
Suitable short-term regimens of antiemetic drugs with 5-HT3–receptor antagonist activity (see Table) include:
1ondansetron 4 to 8 mg intravenously, 8- to 12-hourly if required1 ondansetron ondansetron ondansetron
OR
1ondansetron 4 to 8 mg orally, 8- to 12-hourly if required2. ondansetron ondansetron ondansetron
Suitable short-term regimens of antiemetic drugs with predominantly dopamine antagonist activity (see Table) include:
1metoclopramide 10 mg intramuscularly or intravenously, 8-hourly if required metoclopramide metoclopramide metoclopramide
OR
1metoclopramide 10 mg orally, 8-hourly if required metoclopramide metoclopramide metoclopramide
OR
1prochlorperazine 12.5 mg intramuscularly or by slow intravenous injection, 8-hourly if required3 prochlorperazine prochlorperazine prochlorperazine
OR
1prochlorperazine 20 mg orally, for the first dose, then 10 mg 2 hours later, then 5 to 10 mg orally, 8-hourly if required prochlorperazine prochlorperazine prochlorperazine
OR
2droperidol 0.25 to 0.625 mg intravenously, as a single dose4. droperidol droperidol droperidol
A suitable short-term regimen of an antiemetic drug with predominantly antihistamine activity (see Table) is:
1promethazine hydrochloride 25 mg orally, every 4 to 6 hours if required (maximum 100 mg in 24 hours). promethazine hydrochloride promethazine promethazine
If a patient does not respond to an antiemetic, trial a different antiemetic. Some antiemetics have multiple mechanisms of action, so it may be appropriate to trial a different drug from the same class.
Nasal inhalation of isopropyl alcohol, by inhaling the vapour from a standard disinfectant pad, can be used in patients with mild nausea and vomiting as an alternative to oral therapy. While the mechanism of action is unclear, it appears to be effective for mild nausea and vomiting and is associated with few adverse effectsApril, 2018Beadle, 2016.
Dexamethasone may be preferred for nausea and vomiting caused by cerebral oedema associated with central nervous system tumours, or for nausea and vomiting refractory to other antiemetics.
If nausea and vomiting do not respond to the therapies above, consider other drugs such as domperidone (has a lower risk of central nervous system adverse effects than metoclopramide)Heckroth, 2021, mirtazapine (may be useful for nausea and vomiting associated with functional dyspepsia or gastroparesis) or olanzapine (may be useful for chemotherapy-induced nausea and vomiting).
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5-HT3–receptor antagonists dopamine antagonists antihistamine corticosteroids | |
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5-HT3–receptor antagonists | |
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ondansetron | |
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indications |
general use particularly useful for nausea and vomiting associated with acute gastroenteritis |
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precautions |
rapid intravenous administration can cause visual disturbance can cause headache, constipation and prolongation of the QT interval (dose-dependent effect); rarely associated with dystonic reactions |
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dopamine antagonists | |
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droperidol (a butyrophenone) | |
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indications |
limited use particularly useful for nausea and vomiting refractory to other antiemetics, opioid-induced nausea and vomiting, and anxious or agitated patients |
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precautions |
can cause sedation and extrapyramidal adverse effects, including akathisia; avoid in Parkinson disease |
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metoclopramide (a benzamide) | |
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indications |
general use particularly useful for nausea and vomiting associated with migrainePatanwala, 2010 or acute gastroenteritis |
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precautions |
avoid use in patients younger than 20 years and older persons—acute dystonic reactions are more common in young adults and older persons [NB3] can cause extrapyramidal adverse effects—avoid in Parkinson disease can cause irreversible tardive dyskinesia [NB3][NB4] do not use for longer than 5 days avoid if stimulation of the gastrointestinal tract is dangerous (eg gastrointestinal obstruction or perforation) |
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prochlorperazine (a phenothiazine) [NB5] | |
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indications |
general use particularly useful for nausea and vomiting associated with migraine, motion sickness or acute gastroenteritis |
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precautions |
can cause sedation, prolongation of the QT interval and extrapyramidal adverse effects, including tardive dyskinesia and akathisia; avoid in Parkinson disease can have anticholinergic effects |
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antihistamine | |
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promethazine hydrochloride (a phenothiazine) [NB5] | |
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indications |
general use particularly useful for nausea and vomiting associated with motion sickness |
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precautions |
can cause sedation, lower the seizure threshold and have anticholinergic effects can cause extrapyramidal adverse effects, including tardive dyskinesia; avoid in Parkinson disease avoid parenteral use because there is a risk of tissue necrosis; if an alternative antiemetic cannot be used and parenteral use is required, deep intramuscular injection can be used |
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corticosteroids | |
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dexamethasone | |
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indications |
limited use particularly useful for cytotoxic drug-induced nausea and vomiting, or nausea and vomiting caused by bowel obstruction or raised intracranial pressure |
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precautions |
may cause mood or sleep disturbance; other adverse effects are unlikely with a single dose use with caution in sepsis, haematological malignancy and diabetes |
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Note:
NB1: Antiemetics in this table are recommended for short-term initial management only; the patient must be thoroughly assessed to determine the cause of symptoms. If long-term therapy is required, the patient should be considered to have chronic nausea and management and management should be specific to the cause of the nausea and vomiting (see Assessment of nausea and vomiting for a list of common causes of chronic nausea). NB2: Consider the patient’s comorbidities before prescribing an antiemetic. See text for management of nausea and vomiting during pregnancy, postoperative nausea and vomiting in adults, drug- and radiation-induced nausea and vomiting in adults. NB3: For more information, see the Australian Therapeutic Goods Administration (TGA) Medicines Safety Update. NB4: Metoclopramide carries a risk of irreversible tardive dyskinesia. Patients using metoclopramide for a longer duration (more than 3 months) have an increased risk of tardive dyskinesiaHeckroth, 2021. While recent data show this risk is lower than previously estimated, the risk of tardive dyskinesia should be considered when starting therapyAl-Saffar, 2019. NB5: Phenothiazines block D2-dopamine, M1-muscarinic and H1-histamine receptors to varying degrees. | |