Phenergan (Promethazine) Drug Information: Clinical Pharmacology

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May 27, 2012

Phenergan

Allergy »

Allergy facts

Allergy involves an exaggerated response of the immune system.
The immune system is the body's organized defense mechanism against foreign invaders, particularly infections.
Allergens are substances that are foreign to the body and can cause an allergic reaction.
IgE is the allergy antibody.
Allergies can develop at any age.
Your risk of developing allergies is related to your parents' allergy history.

Introduction

In this review you will learn how allergy relates to the immune system. You will begin understanding how and why certain people become allergic. The most common allergic diseases are discussed briefly in this article.

What does an allergy mean?

An allergy refers to an exaggerated reaction by our immune system in response to bodily contact with certain foreign substances. It is exaggerated because these f...

Read the Allergy article »

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Please Note: This Brand Name drug is no longer available in the US.
(Generic versions may still be available.)

CLINICAL PHARMACOLOGY

Promethazine is a phenothiazine derivative which differs structurally from the antipsychotic phenothiazines by the presence of a branched side chain and no ring substitution. It is thought that this configuration is responsible for its relative lack (1/10 that of chlorpromazine) of dopamine antagonist properties.

Promethazine is an H₁ receptor blocking agent. In addition to its antihistaminic action, it provides clinically useful sedative and antiemetic effects.

Promethazine is well absorbed from the gastrointestinal tract. Clinical effects are apparent within 20 minutes after oral administration and generally last four to six hours, although they may persist as long as 12 hours. Promethazine is metabolized by the liver to a variety of compounds; the sulfoxides of promethazine and N-demethylpromethazine are the predominant metabolites appearing in the urine.

Last reviewed on RxList: 6/21/2007
This monograph has been modified to include the generic and brand name in many instances.