Effect of terfenadine on nasal provocation

Area of Science:

• Allergy and Immunology
• Pharmacology

Background:

• Histamine H1 antagonists are crucial in managing allergic rhinitis.
• Understanding the specific mechanisms of action for antihistamines like terfenadine is important for optimizing treatment.

Purpose of the Study:

• To evaluate the effects of terfenadine on nasal responses to antigen, histamine, and methacholine.
• To determine if terfenadine possesses anticholinergic activity.
• To investigate the role of H1 receptors in histamine-induced nasal secretion.

Main Methods:

• Nasal challenges with antigen, histamine, and methacholine were performed.
• Single-dose and 1-week pretreatment with terfenadine were assessed in a double-blind, placebo-controlled trial.
• Measurements included sneezing, nasal secretion, congestion, histamine levels, kinins, albumin, and TAME esterase activity.

Main Results:

• Terfenadine blocked histamine-induced nasal secretion but had no effect on methacholine response.
• A single dose reduced sneezing and secretion following antigen challenge, but not congestion.
• One-week pretreatment significantly reduced sneezing, kinins, albumin, and TAME esterase activity after antigen challenge.
• Terfenadine also reduced histamine levels post-antigen challenge, suggesting mast cell stabilization.

Conclusions:

• Terfenadine acts as an H1 antagonist with no anticholinergic effects.
• Histamine-induced nasal responses are mediated by H1 receptors.
• Terfenadine effectively alleviates key allergic nasal symptoms and modulates inflammatory markers.