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Iranian Journal of Pharmacology and Therapeutics
Razi Institute for Drug Research (RIDR) of Iran University of Medical Sciences and Health Services (IUMS)
ISSN: 1735-2657
Vol. 1, No. 2, 2002, pp. 20-23
Bioline Code: pt02006
Full paper language: English
Document type: Research Article
Document available free of charge

Iranian Journal of Pharmacology and Therapeutics, Vol. 1, No. 2, 2002, pp. 20-23

 en The Comparative Effects of Four Antihistamines on Isolated Rat Atria
Abbas Pousti, Golrokh Malihi, Azam Bakhtiarian and Zahra Abdollahi


It has been reported that some of H1 receptor antagonists have important effects on cardiovascular system. Terfenadine as a non-sedative H1 receptor antagonist has an arrhythmogenic activity. In this study we have shown the effects of four antihistamine drugs: terfenadine, loratadine, clemastine and diphenhydramine, on the rate and contractions of isolated rat atria. Terfenadine (1-10 μM) caused a negative chronotropic effect (19.5-80%) and arrhythmia after 10 min. followed by a decrease in the contractile force by (7.5%), and finally after 45 min. asystolia occurred. Loratadine (30-150 μM) decreased the rate of contractions (10-82%) after 10 min. the contractile force of atria was decreased (10-19%) after 20 min. Loratadine did not produce any arrhythmia. Diphenhydramine (5-20 μM) produced bradycardia (14.5-43%) after 20 min and decreased the contractile force (2.5-40%) after 40 min. Clemastine (3-10 μM) produced negative chronotropic and inotropic effect by (11.5-42%) and (10-58%) respectively. These findings indicate that all four drugs caused bradycardia and reduced contractile force, but in the case of terfenadine, it also had arrhythmogenic activity. Loratadine had the least cardiotoxic effect.

antihistamines, contractile force, heart rate, cardiotoxi

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