[Tachyphylaxis of airway response to inhaled bradykinin over several days]

Tachyphylaxis of airway responses has been described for a variety of pharmacological stimuli. A decrease in airway responsiveness to inhaled bradykinin has been reported when challenges were repeated within intervals of 60 minutes. Especially within the framework of drug studies, it is important to know whether tachyphylaxis persist over days. The aim of our study was to assess the occurrence of tachyphylaxis to inhaled bradykinin within several days. Thirteen patients with mild extrinsic bronchial asthma were included into the study. We performed two bradykinin inhalation challenges separated by an interval of three days and determined the provocative concentrations of bradykinin (PC20FEV1) which produced a 20% fall in FEV1. Geometric mean of PC20FEV1 was 0.033 mg/mL in the first and 0.105 mg/mL in the second challenge. These values were significantly different (p < 0.05). Our data demonstrate that tachyphylaxis of the airway response to bradykinin persists over a time period of three days.