Evaluation of impaction force of nasal sprays and metered-dose inhalers using the Texture Analyser

The impaction force from an inhalation product is an important characteristics by which to characterize the spray plume. It is one of the plume characteristics that can be perceived by a patient, and is expected to be good measures of local delivery equivalence for inhalation drugs. A Stable Micro Systems TA-XT.plus Texture Analyser equipped with 750 g load cell was used to measure the impaction force of several nasal sprays and metered-dose inhalers (MDIs). A survey of several commercial nasal spray and MDI products shows that impaction forces of these products varies from 1.5 to 6.5 g force and are significantly different from each other. A 3-level, 4-factor Box-Behnken design was applied to the study of impaction force of nasal sprays using placebo solutions. The influences of four factors: actuation stroke length, actuation velocity, concentration of gelling agent, and concentration of surfactant, were investigated. Of those factors examined here, actuation velocity exerts the greatest effect on impaction force. Impaction force is a discriminative parameter for in vitro testing of nasal spray and MDI products. Since impaction force is more directly related to patient sensation and aerosol deposition in the nasal mucus than other, more traditional parameters, it may provide a better way to evaluate in vitro equivalence in support of abbreviated new drug applications (ANDAs) for orally inhaled and nasal drug products.