Cetirizine and loratadine - comparing their antagonist effects on isolated trachea of rabbit

To study and compare the antagonist effects of Cetirizine and Loratadine on histamine induced contractions of isolated trachea of rabbit. Comparative controlled invitro experimental 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. 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. 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. Cetirizine found more potent than Loratadine as inhibitor of histamine induced contraction in isolated tracheal smooth muscles of rabbit. Basic Sciences

Verapamil and loperamide; to compare the inhibitory effects on isolated guinea pig ileum

In smooth muscle cells, an increase in cytosolic free calcium concentration is an essential step for the cells to contract. The increase in calcium concentration occurs by influx from the extra cellular medium through calcium ion channels. Calcium channels have potential role in regulation of motility in gastrointestinal tract so there is growing interest in calcium channel blockers as a potential pharmacological approach to the treatment of various gastrointestinal motor disorders. In this study we evaluate the inhibitory effects of verapamil on spontaneous contractions of isolated guinea pig ileum and compare them with inhibitory effects of loperamide. Isolated intestinal segments of sixteen guinea pigs were used in this study. Serial dilutions [10-18 -10-3 gm/ml] of loperamide and verapamil were administered; effects observed and recorded by 7B Grass Polygraph machine. We observed that at lower concentrations, loperamide showed more inhibitory effects than verapamil while at higher concentrations [10-4 and 10-3 gm/ml] verapamil showed more inhibitory effects than loperamide on the contractions of isolated guinea pig ileum. This study gave us a clue that verapamil found a potent inhibitor of small intestinal contractions as loperamide. However one can presume further that calcium channel blocker verapamil acting on calcium channel receptor on GIT will be developed with more specific effects on smooth muscle of intestinal tract