Antihistamine Injections

  • 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: Charles Patrick Davis, MD, PhD
    Charles Patrick Davis, MD, PhD

    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

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Effects of antihistamines are prolonged if combined with MAO inhibitors like:

Antihistamine injections should be used with caution with MAO inhibitors.

What formulations of antihistamine injections are available?

Antihistamine injections are available in injection form.

  • Diphenhydramine, promethazine, and dimenhydrinate are administered intramuscularly and intravenously.
  • Hydroxyzine hydrochloride is administered only intramuscularly.
  • Antihistamine injections are not recommended for administration via subcutaneous route.

What about taking antihistamine injections during pregnancy or while breastfeeding?

FDA lists diphenhydramine and dimenhydrinate as Pregnancy Category B and promethazine as Pregnancy Category C. Hydroxyzine does not have a Pregnancy Category. These categories mean that the safe and effective use of antihistamine injections is not established in during pregnancy; therefore, they should be used only if clearly needed.

It is not known whether injected antihistamine medication enters breast milk; therefore, it is best to be cautious before using antihistamine injections in women who are breastfeeding.

REFERENCE: FDA Prescribing Information.

Medically Reviewed by a Doctor on 11/18/2014

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