Ventilatory effects of selective beta 1-(prenalterol) or beta 2-(salbutamol) adrenoceptor agonism in man

We compared the ventilatory effects of prenalterol (beta 1-selective adrenoceptor agonist) with those of salbutamol (beta 2-selective adrenoceptor agonist) in 6 healthy volunteers. Two intravenous doses of prenalterol (1 mg/60 min, 2 mg/60 min) and of salbutamol (300 micrograms/60 min, 600 micrograms/60 min) were given in random order in 4 separate sessions of 60 minutes each. Pulmonary ventilation per minute (V'E) increased only on the high dose of salbutamol. Mouth occlusion pressure (P0.1) did not vary either on prenalterol or on salbutamol. Only the high dose of salbutamol induced (1) an increase in tidal volume (VT) without changes in respiratory rate (RR), (2) an increase in mean inspiratory flow (VT/Ti) without changes in the fraction of inspiratory time to total cycle duration (Ti/Ttot). During forced expiration, salbutamol elicited a small bronchodilating effect at the level of both large (FEV1, FEF25-75, FEF50) and small (FEV3, FEF75-85, FEF75) airways. Prenalterol induced a very small dilatation of the large airways, and a somewhat more pronounced effect at the level of the small airways. Neither the indexes of ventilatory pattern nor those of bronchial tone showed any statistical or biological differences between values on prenalterol and values on salbutamol. However, both the former and the latter indexes showed a trend to be higher on salbutamol than on prenalterol. Results suggest that salbutamol-induced increase in pulmonary ventilation per minute in subjects without bronchial obstruction is likely the result of a reduced bronchomotor tone at rest, leading to an increase in tidal volume because of the rise in the VT/Ti ratio.(ABSTRACT TRUNCATED AT 250 WORDS)