The emitted dose of drug from a valved holding chamber using five pressurized metered dose inhalers

Background. The dose available at the mouth from a pressurised metered-dose inhaler (pMDI) cannot stay the same if it is used with a valved holding chamber (VHC). A different aerosol drug delivery system is created when the pMDI is used with the VHC and therefore the dose delivered to the patients is no longer that released from the pMDI alone, but the one emitted by the new system. This study aims to verify the emitted dose of five pMDI drugs when used with a VHC. Methods. The emitted dose was expressed as the amount of drug within the respirable fraction available at the end of the VHC, i.e. the drug output (measured by high performance liquid chromatography) multiplied by the percentage of FDF determined using a laser diffraction analyser. Results. the emitted doses were drastically reduced in comparison with the nominal doses (Beclomethasone from 250 to 90.5 µg, Budesonide from 200 to 100 µg, Ciclesonide from 160 to 102 µg Fluticasone from 250 to 116 µg, Salbutamol from 100 to 54 µg). Conclusions. When pMDIs are employed with a VHC, the emitted dose drastically changes; it is more or less halved. In order to facilitate prescription by the physician, both the nominal and the emitted doses should be reported in the VHC package.