promethazine, Phenergan, Phenadoz, Promethegan

  • Pharmacy Author:
    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: Jay W. Marks, MD
    Jay W. Marks, MD

    Jay W. Marks, MD

    Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

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GENERIC NAME: promethazine

BRAND NAME: Phenergan, 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.

PRESCRIBED FOR: Promethazine is prescribed for treating nausea or vomiting, motion sickness, and allergic reactions and for sedation prior to or after surgery.

Medically Reviewed by a Doctor on 9/14/2015

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