Cetirizine & Loratadine - Comparing Their Antagonist Effects on Isolated Trachea of Rabbit

Abstract

Objective: To study and compare the antagonist effects of Cetirizine and Loratadine on histamine induced 
contractions of isolated trachea of rabbit. 
Study Design: Comparative controlled invitro experimental study.  
Place and Duration of Study: This study was conducted at The Department of Pharmacology and Therapeutics, 
Basic Medical Sciences Institute (BMSI), Jinnah Postgraduate Medical Center (JPMC) Karachi, for the period of six 
months. 
Materials and Methods: Isolated tracheal smooth muscles of twenty four rabbits were used. Fresh Kreb’s 
nutritional solution was prepared for each subject. Tracheal smooth muscles were exposed to standard dilution of 
Histamine, and then they were challenged with serial dilutions (10-18 to 10-3 gm /ml) of Cetirizine and Loratadine 
separately. Responses as rate and amplitudes of contractions were recorded by 7B Grass Polygraph machine. 
Results: Cetirizine inhibit the rate of histamine induced contractions of tracheal muscles from 0.85 to 12.33 % and 
amplitude from 0.0 to 82.69 %, as concentration of drugs increased. While Loratadine inhibit the rate of histamine 
induced tracheal contractions from 0.85 to 10.59 % and amplitude from 6.5 to 76.82 % as concentration of drugs 
increased. 
Conclusion: Cetirizine found more potent than Loratadine as inhibitor of histamine induced contraction in isolated 
tracheal smooth muscles of rabbit.