Effects of ketotifen, a benzocycloheptathiophene, on metacholine- and acetylcholine-induced contractions of canine respiratory smooth muscle.
The relaxant effects of ketotifen on isolated respiratory smooth muscle contracted by methacholine or acetylcholine were examined. Although potent dose-dependent relaxation was observed, it appears that more than 100 times the concentration is required to relax muscle contracted with cholinergic agonists than has been reported for muscle contracted by histamine. This observation offers a possible explanation for the findings of several investigators that dosages of ketotifen administered to patients protect against histamine-induced, but not methacholine- or acetylcholine-induced, bronchospasm.
D000109:Acetylcholine / Q000037:antagonists & inhibitors*; D000403:Airway Resistance / Q000187:drug effects*; D000818:Animals; D004285:Dogs; D066298:In Vitro Techniques; D007665:Ketotifen / Q000494:pharmacology*; D016210:Methacholine Chloride; D008688:Methacholine Compounds / Q000037:antagonists & inhibitors*; D009130:Muscle, Smooth / Q000187:drug effects; D014132:Trachea / Q000187:drug effects
D008688:Methacholine Compounds; D016210:Methacholine Chloride; D000109:Acetylcholine; D007665:Ketotifen