RELATIVE BIOAVAILABILITY OF SALBUTAMOL TO THE LUNG FOLLOWING INHALATION VIA A NOVEL DRY POWDER INHALER AND A STANDARD METERED-DOSE INHALER

Aims The number of dry powder inhaler (DPI) devices could increase bec ause they are easier to use than a metered dose inhaler (MDI). Using u rinary excretion, the relative bioavailability of salbutamol to the lu ngs and the body for a prototype DPI has been compared with an MDI. Me thods A randomized, double-blind, two way crossover study compared the amount of salbutamol in the urine 30 min following inhalation of 2 x 100 mu g salbutamol from a prototype DPI (Innovata Biomed Ltd, UK) and a Ventolin(R) (Allen and Hanburys Ltd, UK) MDI in 10 volunteers. The amount of salbutamol and its metabolite, the ester sulphate conjugate, renally excreted up to 24 h post inhalation was also determined to ev aluate the relative bioavailability of salbutamol to the body. Results The mean (s.d.) 30 min post-treatment urinary excretion for the proto type DPI and MDI was 8.4 (2.6) and 5.0 (1.9) mu g, respectively (P<0.0 01). The total amount of salbutamol and its ester metabolite excreted in the urine over the 24 h period after inhalation was 187.9 (77.6) an d 137.6 (40.0) mu g (P<0.05). Conclusions The prototype DPI delivered more salbutamol to the body and the lungs than a conventional MDI. Thi s finding supports further development of the prototype DPI. The urina ry salbutamol method is able to discriminate between two different inh alation systems.