A comparison of the lung deposition of salbutamol inhaled from a new dry powder inhaler, at two inhaled flow rates

Abstract

A method of radiolabelling micronised salbutamol with 99mTc and blending it with lactose, for use in a multidose dry powder inhaler (Pulvinal, Chiesi) was developed. In vitro experiments with a multistage liquid impinger demonstrated that the labelling process did not affect the particle size distribution of the drug, and that the radiolabel was a marker for the drug substance across a range of particle sizes. Gamma scintigraphy was used to measure the in vivo deposition of salbutamol in 10 healthy volunteers, at a fast peak inhaled flow rate (mean 46.0 l/min) and at a slow peak inhaled flow rate (27.8 l/min). A significantly higher percentage of the dose ( p=0.05) was deposited in the lungs at the fast flow rate (14.1 ± 3.2%) compared to the slow flow rate (11.7 ± 2.3%). Deposition patterns within the lung regions were similar at the two flow rates. The major site of deposition was the oropharynx, and approx. 1% of the dose was exhaled. The deposition patterns from the Pulvinal inhaler were similar to those observed previously both for other powder inhalers and for pressurised metered dose inhalers.