Antihistamines inhibit the effects of histamine at H1 receptors. They have a number of clinical indications including allergic conditions (e.g., rhinitis, dermatoses, atopic dermatitis, contact dermatitis, allergic conjunctivitis, hypersensitivity reactions to drugs, mild transfusion reactions, and urticaria), chronic idiopathic urticaria (CIU), motion sickness, vertigo, and insomnia.

First-generation antihistamines are highly lipophilic and therefore readily cross the blood-brain barrier, contributing to adverse central nervous system effects, including sedation, drowsiness, and decreased cognitive processing.

Newer antihistamines were developed to decrease the adverse effects of first generation drug. "Second generation" antihistamines have higher specificity for binding to H1 receptors, lower affinity for non-histamine receptors, and are lipo-phobic (thus have poor penetration of the blood brain barrier). Third generation antihistamines are natural metabolites of first generation drugs, developed with the goal of improving clinical efficacy and minimizing side-effects. The purpose of this review was to compare the efficacy, effectiveness, and adverse effects of newer antihistamines in both adult and pediatric populations.

Contents

• Introduction
  • Rhinitis
  • Urticaria
  • Purpose and Limitations of Systematic Reviews
  • Scope and Key Questions
• Methods
  • Study Selection and Inclusion Criteria
  • Literature Search
  • Data Abstraction
  • Study Selection
  • Validity Assessment
  • Data Synthesis
  • Public Comment
• Results
  • Overview
  • Key Question 1. For outpatients with seasonal or perennial allergic rhinitis or urticaria, do newer antihistamines differ in effectiveness?
  • Key Question 2. For outpatients with seasonal or perennial allergic rhinitis or urticaria, do newer antihistamines differ in harms?
  • Key Question 3. Are there subgroups of patients based on demographics (age, racial groups, gender), concomitant medications (drug-drug interactions), co-morbidities (drug-disease interactions or pregnancy), for which one newer antihistamine is more effective or associated with fewer harms?
• Summary of the Evidence
• References
• Appendix A Glossary
• Appendix B Search strategy for Update 2
• Appendix C Methods used to assess quality of studies
• Appendix D Excluded studies in Update 2
• Appendix E Reporting of adverse events
• Appendix F Poor-quality studies
• Evidence Tables

Original Report: November 2004
Update 1: April 2006

The medical literature relating to this topic is scanned periodically. (See http://www.ohsu.edu/ohsuedu/research/policycenter/DERP/about/methods.cfm for description of scanning process). Prior versions of this report can be accessed at the DERP website.

Drug Effectiveness Review Project
Marian McDonagh, PharmD, Principal Investigator
Oregon Evidence-based Practice Center
Mark Helfand, MD, MPH, Director
Oregon Health & Science University

The Drug Effectiveness Review Project, composed of 12 organizations including 11 state Medicaid agencies and the Canadian Agency for Drugs and Technology in Health commissioned and funded for this report. These organizations selected the topic of the report and had input into its Key Questions. The content and conclusions of the report were entirely determined by the Evidence-based Practice Center researchers. The authors of this report have no financial interest in any company that makes or distributes the products reviewed in this report.

Suggested citation:

Carson S, Lee N, Thakurta S. Drug class review: Newer antihistamines. Update 2.

The purpose of Drug Effectiveness Review Project reports is to make available information regarding the comparative clinical effectiveness and harms of different drugs. Reports are not usage guidelines, nor should they be read as an endorsement of or recommendation for any particular drug, use, or approach. Oregon Health & Science University does not recommend or endorse any guideline or recommendation developed by users of these reports.