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Aerodynamic Particle Size Distribution (APSD)

Together with delivered dose, aerodynamic particle size distribution (APSD) is typically identified as a Critical Quality Attribute (CQA) for orally inhaled and nasal drug products (OINDPs) making it a primary focus for in vitro characterisation. The APSD of an OINDP defines how particles behave in a moving air stream. It is intuitively relevant to the understanding of likely lung deposition and hence potential drug efficacy. Typically particles should be in the range of 1 to 5 microns to be effective, any larger than 5 microns and they are likely to impact the oropharynx and be swallowed, any smaller than 1 micron and it is possible that the particles will remain entrained in the air system.

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Aerodynamic Particle Size Distribution

Please select an OINDP type for further information about Aerodynamic Particle Size Distribution (APSD) measurement.

APSD of Metered Dose Inhalers (MDIs)

The APSD testing of MDIs is typically performed at a flow rate of 28.3 L/min when using an ACI or 30 L/min when using an NGI. For Breath Actuated MDIs (BAIs) a Breath Actuation Controller may also be used to generate a time delay. However, it must be noted that when add-on devices such as spacers or valved holding chambers (VHCs) are used, the APSD characteristics may be substantially altered from what is emitted when the MDI is used alone and must be assessed appropriately.

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APSD of Dry Powder Inhalers (DPIs)

The APSD measurement of DPIs is typically performed under the same conditions as DDU testing, however a Preseparator is typically interposed between the induction port and stage 0 of cascade impactor to capture the large, non-inhalable carrier particles, to prevent impactor over-loading. As for delivered dose testing of DPIs, test flow rate is set on the basis of a 4 kPa pressure drop across the device, to approximate the mean patient inhalation flow rate achieved during clinical use.

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DPIs

APSD of Nebulisers

For devices such as nebulisers, the evaporation of droplets exacerbated by the thermal mass of the impactor can be a problem, especially for drugs in solution. Loss of solvent reduces droplet size, producing artificially low APSD measurements, compromising the integrity of the resulting data. Cooling the impactor to approximately 5°C is the recommended method for overcoming this problem.

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ASPD of Nebulisers

APSD of Aqueous Droplet Inhalers (ADIs)

For ADIs as for nebulisers, the evaporation of droplets exacerbated by the thermal mass of the impactor can be a problem. Loss of solvent reduces droplet size, producing artificially low APSD measurements, compromising the integrity of the resulting data. Cooling the impactor to approximately 5°C is the recommended method for overcoming this problem.

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ADIs

APSD of Nasal Products

Nasal sprays, nasal aerosols and nasal powders typically produce droplets in the range of 20-200 microns, which is outside the effective range of cascade impactors. However, each may deliver a proportion of fine droplets in the <10 micron range. It is important to quantify this FPD since it can penetrate beyond the nasal tract and into the lower respiratory tract or lungs, which may be undesirable.

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Related Inhaler Testing Products

For further information about the other products in our inhaler testing range, please select one of the options below.

Aerodynamic Particle Size Distribution (APSD)

Our range of precision engineered cascade impactors measure the size distribution (particle size) of inhaled drug products, providing critical information about where particles in aerosol clouds are likely to be deposited in the lungs following inhalation.

Aerodynamic Particle Size Distribution (APSD)

APSD Data Analysis Software

Inhalytix® – Efficiently converts raw APSD data into performance-defining metrics for all OINDPs

APSD Data Analysis Software

Ancillaries

Optimise inhaler testing workflows with our broad range of supporting equipment required to make up fully-operating test systems for Delivered Dose Uniformity (DDU) and Aerodynamic Particle Size Distribution (APSD) of orally inhaled and nasal drug products (OINDPs).

Ancillaries

Special Applications

Copley Scientific offers a range of testing equipment for additional qualification and validation of orally inhaled and nasal drug products (OINDPs), including assessments of generic drug formulations, inhaled dissolution testing and improving IVIVCs.

Special Applications

Semi-Automation

Take the labour out of inhaler testing with our semi-automated solutions.

Semi-Automation

Improving IVIVCs

Better in vitro – in vivo correlation (IVIVC) has long been an industry aim. This is particularly difficult in the case of inhaled and nasal products because of the complications involved in precisely correlating drug deposition behaviour with clinical efficacy, the impact of patient-to-patient variability and the complex interaction between formulation and device. One strategy for improving the significance of cascade impaction data is to modify the test set-up in order to mimic the in vivo d