Influence of route of administration and dosage form in the pharmacokinetics and bioavailability of salbutamol.

The present study was carried out to define the pharmacokinetics of salbutamol sulfate administered to mongrel dogs in five pharmaceutical forms via two routes of administration. One pharmaceutical form was administered intravenously (Ventolin i.v.) while the other four were administered orally (Ventolin: immediate-release formulation, Volmax: commercial osmotic pump, SG7 and SG14: sustained-release hydrophilic matrices developed in our laboratory). We obtained a first-order release kinetic of the salbutamol from Ventolin and SG7, whereas a zero-order release kinetic was observed for SG14 and Volmax formulations. Oral bioavailability was 80% and there were neither significant differences (P > 0.05) in terms of the calculation method used (relation of the areas under the plasma level curve Loo-Riegelman, deconvolution) nor in terms of the dosage form (Ventolin Volmax, SG7 and SG14). The elimination half-life value of salbutamol was 1.2 h when administered intravenously; this parameter had a value of 3.0 h for the immediate-release formulation and ranged between 5.4 and 7.2 h in the sustained-release formulations when administered orally. These changes in the half-life value of the sustained-release formulations will allow us to modify the frequency of administration in relation to immediate-release formulations.