Inhalation Product Analysis & Testing

The devices used for inhaled and nasal drug delivery are collectively referred to as Orally Inhaled and Nasal Drug Products (OINDPs). The range of products available is broad, encompassing inhalers (metereddose, dry powder and aqueous droplet), nebulisers (jet, ultrasonic and vibrating mesh) and nasal (aqueous based, dry powder and propellant based). Apart from the mandatory testing for leachables & extractables and microbial contaminants, two of the main factors largely recognised as Critical Quality Attributes (CQAs) in the testing of OINDPs (in both pharmaceutical development and batch release) are:

  • Delivered Dose (Emitted Dose) by means of Dosage Unit Sampling Apparatus (DUSA): the total amount of drug emitted from the drug device and hence available to the user. Its uniformity is a Critical Quality Attribute (CQA) in determining the safety, quality and efficacy of an orally inhaled and nasal drug product (OINDP).
  • Particle Size (Aerodynamic Size Distribution) by means of Andersen Cascade Impactor or New Generation Impactor (NGI): this test is used to determine the fine particle characteristics of the aerosol clouds generated by preparations for inhalation. Particle size determines the percentage of the total emitted dose that actually reaches the lungs or nasal mucosa during inhalation and is thus, therapeutically effective.

Instrumentation:

Multistage cascade impactors are used to size-fractionate a sample on the basis of particle inertia, uniquely enabling measurement of the particle-size distribution of the active ingredient, rather than of the complete formulation. The resulting information is crucial when assessing the likely deposition behavior of the drug during inhalation and is also widely taken to be an in vitro indicator of delivery efficiency.

The most widely used full resolution cascade impactors (e.g., Andersen Cascade Impactor and New Generation Impactor) separate a sample into 7–8 discrete size fractions depending on the set-up used. Analysis of each fraction, typically by high-performance liquid chromatography (HPLC), determines the amount of active ingredient collected at each stage.

These two physical tests form the basis of many of the parameters used by the regulators to characterise inhalation and nasal products; both of them could be performed in Pharmaprogress by personnel with specific training.

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