Actions of SDZ PCO 400 and cromakalim on airway smooth muscle in vivo.

SDZ PCO 400, and cromakalim are potassium channel opening drugs which relax airway smooth muscle and reverse airway obstruction due to intravenous administration of airway spasmogens. Reduction of airway obstruction by these drugs may be attributed to actions upon airway reactivity as well as airway smooth muscle spasmolysis; for, at concentrations which do not induce overt relaxation of airway smooth muscle, both SDZ PCO 400 and cromakalim suppressed development of airway hyperreactivity due to administration of immune complexes, PAF or (+/-)isoprenaline and reversed established airway hyperreactivity due to allergic reactions. When administered as aerosols prior to inhalation of allergen in actively sensitized guinea-pigs, or by the oral route in guinea-pigs with idiopathic eosinophilia, neither cromakalim nor SDZ PCO 400 influenced the influx of eosinophils into the airway lumen. Thus, SDZ PCO 400 and cromakalim may readily be distinguished from established prophylactic anti-asthma drugs such as cromoglicate and ketotifen. By influencing airway reactivity, potassium channel openers provide a novel approach to the resolution of airway obstruction in asthma.