DDU of Metered-Dose Inhalers (MDIs)
MDI aerosol characteristics are relatively insensitive to changes in air flow rate because the aerosolisation and dispersion mechanisms are dependent on the force generated by the propellant, rather than the patient’s inspiratory effort. Therefore, for MDIs, the test flow rate is fixed at an arbitrary value of 28.3 L/min. A vacuum pump is used to draw air through the assembled test set-up at this flow rate. However, these test conditions are not applied for DDU testing when the MDI is intended for use with an add-on device such as a spacer or valved holding chamber (VHC).
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The constant 28.3 L/min air flow rate applied during the testing of MDIs is replaced by a specific patient relevant tidal breath profile more representative of the conditions applied by the patient when using an add-on device.
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We also offer a range of equipment for additional MDI testing application support:
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One of the main factors influencing the amount of inhaled drug available to the patient is the interface between the facemask and the patient. Investigating and defining the effect of a facemask to the product’s DDU and APSD is important for the product development.
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