Pharmacokinetics and systemic β 2-adrenoceptor-mediated responses to inhaled salbutamol

Aims: To examine whether systemic β ₂-adrenoceptor responses, such as tachycardia, tremor and hypokalaemia, can be used as a surrogate for the 20 min pharmacokinetic profile of inhaled salbutamol. Methods: A retrospective analysis of eight separate published studies in healthy volunteers was performed, each with an identical protocol evaluating the early lung absorption profile of a nominal 1200 μg dose of salbutamol given by different inhaler devices. Peak postural finger tremor, plasma potassium and heart rate were assesssed. Results: We found the maximum (C _max) and average (C _av) plasma concentrations) of salbutamol to be correlated (P < 0.0001) to change in plasma potassium (C _max r = 0.904; C _av r = 0.899) and tremor (C _max r = 0.875; C _av r = 0.857). No significant) correlations existed between change in heart rate and C _max (r = 0.425) or C _av (r = 0.415). Conclusions: Systemic β ₂-adrenoceptor responses, in particular hypokalaemia and tremor, but not heart rate, appear to be good surrogates for evaluating the lung delivery of inhaled salbutamol. Consequently it is suggested that potassium or tremor responses may be used to evaluate the relative lung delivery of salbutamol from different inhaler devices.