promethazine, Phenergan (Discontinued brand), Phenadoz, Promethegan
Omudhome Ogbru, PharmD
Omudhome Ogbru, PharmD
Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.
Medical and Pharmacy Editor:
GENERIC NAME: promethazine
BRAND NAME: Phenergan (Discontinued brand), Phenadoz, Promethegan
DRUG CLASS AND MECHANISM: Promethazine is a phenothiazine in the same drug class as chlorpromazine (Thorazine) and trifluoperazine (Stelazine). However, unlike the other drugs in this class, promethazine is not used as an anti-psychotic. It used as an anti-histamine, sedative, and antiemetic (anti-nausea). The body releases histamine during several types of allergic reactions. When histamine binds to its receptors on cells, it stimulates changes within the cells that lead to sneezing, itching, and increased mucus production. Antihistamines such as promethazine compete with histamine for one of the receptors for histamine (the H1 receptor) on cells. However, when the antihistamines bind to the receptors they do not stimulate the cells. Instead, they prevent histamine from binding and stimulating the cells. Promethazine also blocks the action of acetylcholine (anticholinergic effect), and this may explain its benefit in reducing the nausea of motion sickness. It is used as a sedative because it causes drowsiness as a side effect. The FDA approved promethazine in 1951.
GENERIC AVAILABLE: Yes
STORAGE: Tablets, syrup and injection should be stored at room temperature, between 15 C to 25 C (68 F to 77 F). Suppositories should be stored at 2 C to 8 C (36 F to 46 F).
PRESCRIBED FOR: Promethazine is prescribed for treating nausea or vomiting, motion sickness, and allergic reactions and for sedation prior to or after surgery.
DRUG INTERACTIONS: Promethazine should not be taken with any of the MAO (mono-amine oxidase) inhibitor-class of antidepressants, for example, isocarboxazid (Marplan), phenelzine (Nardil), tranylcypromine (Parnate), and procarbazine (Matulane), because of the increased risk of extrapyramidal symptoms (EPS)--uncontrollable movement disorders.
Excessive anti-cholinergic effects (described below) can occur when promethazine is used with other antihistamines, for example, diphenhydramine (Benadryl); some phenothiazines, for example, thioridazine (Mellaril); some tricyclic antidepressants, for example, amitriptyline (Elavil), clozapine (Clozaril), cyclobenzaprine (Flexeril), and disopyramide (Norpace).
Excessive sedation may occur when promethazine is combined with other medications that depress the central nervous system (brain) and cause sedation. Such drugs include ethanol, barbiturates, anti-anxiety medications, sedatives, other phenothiazines, and narcotic pain medications. Promethazine should not be combined with amiodarone (Cordarone), sotalol (Betapace), pimozide (Orap), quinidine, and procainamide because of an increased risk of abnormal heart beats.
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