Particle size inhalation dosage forms

MDI products are subject to batch control and acceptance tests similar to those for other pharmaceutical dosage forms, that is, active drug identification, dose delivery, and dose uniformity. Additional special tests unique to inhalers, e.g., characterizing the particle size distribution of the delivered aerosol, are also applied. Typical tests are shown in Table 3. 

As a consequence of the suppression or reduced use of CFC propellants, a new kind of dosage form is under worldwide development drug powder inhalers (DPIs). The metered dose inhalers (MDIs) will probably be replaced by these. The MDIs were formulated several years ago. A drug in powder form (with a particle size close to 5 pm) was suspended in propellant 11 with a surfactant. Propellant 12 was added to the can after closure. 

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