Pharmacokinetics and relative bioavailability of salbutamol metered-dose inhaler in healthy volunteers.

Aim: To study the pharmacokinetics and relative bioavailability of salbutamol metered-dose inhaler (MDI) in healthy volunteers.

Methods: An HPLC method for the determination of salbutamol in human plasma was improved. Ten healthy male Chinese volunteers were enrolled in a randomized crossover study. After the subjects inhaled or orally administered 1.2 mg salbutamol, fourteen blood samples were collected at predetermined time points. The concentrations of salbutamol in plasma were assessed with non-compartment model to obtain the pharmacokinetic parameters. The relative bioavailability of MDI versus water solution was calculated.

Results: The HPLC assay was sensitive, specific, accurate, and precise. The pharmacokinetics of salbutamol MDI was described well with two-compartment model. The parameters for salbutamol inhaled and orally administered were as following: T(max) (0.22+/-0.07) and (1.8+/-0.6) h, C(max) (3.4+/-1.1) and (3.9+/-1.4) microg/L, T(1/2) (4.5+/-1.5) and (4.6+/-1.1) h, AUC0-20 min (0.9+/-0.3) and (0.16+/-0.10) microg x h x L(-1), respectively. There were significant differences in T(max) and AUC0-20 min between the two dosage forms. The AUC0-20 min (inhal) was 8 times as high as the AUC0-20 min (po). The relative bioavailability of salbutamol MDI was 57 %+/-24 % compared with oral solution.

Conclusion: The absorption process of salbutamol MDI in human was significantly different from that of oral solution.