A drug may be classified by the chemical type of the active ingredient or by the way it is used to treat a particular condition. Each drug can be classified into one or more drug classes.

Phenothiazine antiemetics inhibit dopamine, muscarinic and histamine (H1) receptors generally in the vomiting center and chemoreceptor trigger zone. Phenothiazine antiemetics are used to prevent and treat nausea and vomiting caused bycytotoxic drugs and radiotherapy.