Antiemetic drugs are used to treat nausea and vomiting due to a variety of causes and have a wide range of pharmacological properties. The choice of drug will, therefore, depend in part on the condition being treated. The drugs can be classified as dopamine antagonists (including phenothiazines and nonphenothiazines). corticosteroids, cannabinoids, benzodiazepines, serotonin antagonists, antihistamines and anticholinergics.There is very little evidence of a relationship between plasma drug contentrations and either their efficacy or the incidence of adverse effects with most antiemetic drugs. With drugs for which concentration-effect studies have been performed, e.g. the benzodiazepines and antihistamines, the effects monitored have not been directly relevant to their use as antiemetics.Antiemetics are used widely, for example, in cancer chemotherapy. Nonetheless, apart from metoclopramide, little work has been done on the influence of indicators of systemic disease on the pharmacokinetics of antiemetic drugs.