Stop using the flotation technique and start weighing salbutamol pressurised metered-dose inhalers without dose counters

Abstract

Salbutamol pressurised metered-dose inhalers (pMDIs) are not equipped with dose counters outside the USA. The aim of this study was to describe a simple reproducible method for determining the number of doses remaining in a pMDI based on scale weight. With a laboratory scale, the mean weight of the canisters was 28.61 ± 0.10 g after priming and 14.84 ± 0.23 g after 200 puffs. Similar results were obtained with two common digital scales. We recommend weighing salbutamol canisters on a common digital scale, and replacing an old pMDI with a new one when the weight falls to ≤15 g.

Keywords

• pressurised metered-dose inhalers
• dose counter