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 second 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.

The following key questions guided this review:

1. For outpatients with seasonal or perennial allergic rhinitis or urticaria, do newer antihistamines differ in effectiveness?
2. For outpatients with seasonal or perennial allergic rhinitis or urticaria, do newer antihistamines differ in safety or adverse effects?
3. Are there subgroups of patients based on demographics (age, racial groups, gender), other medications (drug-drug interactions), comorbidities (drug-disease interactions), or pregnancy for which one newer antihistamine is more effective or associated with fewer adverse effects?

Contents

• Introduction
  • Rhinitis
  • Urticaria
  • Scope and Key Questions
• Methods
  • Literature Search
  • Study Selection and Inclusion Criteria
  • Data Abstraction
  • Validity Assessment
  • Data Synthesis
• Results
  • Key Question 1. For outpatients with SAR, PAR, or urticaria, do newer antihistamines differ in effectiveness?
  • Key Question 2. For outpatients with SAR, PAR or CIU do newer antihistamines differ in safety or adverse effects?
  • Adverse Events
  • 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 adverse effects?
• Summary
• Discussion
• References
• Appendixes
  • Appendix A. Search Strategies for Newer Antihistamines
  • Appendix B. Quality assessment methods for drug class reviews for the Drug Effectiveness Review Project
  • Appendix C. Poor Quality Studies
  • Appendix D. Abbreviations used in this report
• Evidence Tables

Oregon Evidence-based Practice Center, Oregon Health & Science University, Mark Helfand, MD, MPH, Director

The funding source, the Center for Evidence-based Policy, is supported by 17 organizations, including 15 state Medicaid programs. These organizations selected the topic and had input into the Key Questions for this review. The content and conclusions of the review are 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:

Drug Class Review on Newer Antihistimines. Final Report Update 1. http://derp.ohsu.edu/about/final-products.cfm

The purpose of this report is to make available information regarding the comparative effectiveness and safety profiles of different drugs within pharmaceutical classes. 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.