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Preserved bronchial dilatation after salbutamol does not guarantee protection against bronchial hyperresponsiveness
Author(s) -
Sjöswärd Kerstin Naidu,
Josefsson Martin,
Ahlner Johan,
Schmekel Birgitta
Publication year - 2003
Publication title -
clinical physiology and functional imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.608
H-Index - 67
eISSN - 1475-097X
pISSN - 1475-0961
DOI - 10.1046/j.1475-097x.2003.00462.x
Subject(s) - salbutamol , medicine , bronchial hyperresponsiveness , asthma , agonist , anesthesia , bronchodilator , inhalation , bronchodilator agents , receptor , respiratory disease , lung
Summary Racemic salbutamol, a β 2 ‐adrenoceptor agonist used for dilatation of airways, has recently been shown to induce lessened relaxation of bronchial smooth muscle and partial loss of bronchoprotection, seen as increased hyperresponsiveness, after regular treatment. The racemate undergoes stereo‐selective disposition, giving higher plasma levels of S ‐salbutamol than that of bronchodilating R ‐salbutamol, thus raising S : R ratios after repeated administration. Our aim was to evaluate whether increased bronchial hyperresponsiveness (BHR) could be found even after 1 day of repeated salbutamol inhalations, with β 2 ‐receptor‐induced bronchial smooth muscle relaxation remaining and whether this would be associated with plasma levels of either enantiomer. Fifteen patients with stable asthma, aged 19–54 years, were included in a randomized, cross‐over study. An indirect bronchial challenge method was used [voluntary isocapnic hyperventilation of cold air (IHCA)], and airway condition tested by means of impulse oscillometry. Racemic salbutamol was inhaled three times during a 6‐h period. IHCA was performed and plasma concentrations of enantiomers were measured 4 h after the last dose. Tests were also performed without preceding drug treatment. β 2 ‐Agonist‐produced bronchial dilatation and protection persisted in the majority of the 15 patients 4 h after repeated inhalations of salbutamol during 1 day. In only two of the 15 patients we could trace increased BHR after salbutamol. Neither dilatation nor protection could be linked to plasma levels of either R ‐ or S ‐salbutamol. The underlying mechanisms of BHR remain unknown and are dissociated from β 2 ‐receptor‐mediated dilatation.