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relevant references

SCIENTIFIC JOURNALS

Doub WH, Shah V, Limb S, Guo C, Liu X, Ngo D.; “Developing an in vitro understanding of patient experience with hydrofluoroalkane-metered dose inhalers.”; J Pharm Sci. 2014 Nov;103(11):3648-3656. doi: 10.1002/jps.24167. Epub 2014 Sep 16. PMID: 25228114

ABSTRACT: As a result of the Montreal Protocol on Substances that Deplete the Ozone Layer, manufacturers of metered dose inhalers began reformulating their products to use hydrofluoroalkanes (HFAs) as propellants in place of chlorofluorocarbons (CFCs). Although the new products are considered safe and efficacious by the US Food and Drug Administration (FDA), a large number of complaints have been registered via the FDA’s Adverse Events Reporting System (FAERS)—more than 7000 as of May 2013. To develop a better understanding of the measurable parameters that may, in part, determine in vitro performance and thus patient compliance, we compared several CFC- and HFA-based products with respect to their aerodynamic performance in response to changes in actuator cleaning interval and interactuation delay interval. Comparison metrics examined in this study were: total drug delivered ex-actuator, fine particle dose (<5 µm), mass median aerodynamic diameter, plume width, plume temperature, plume impaction force, and actuator orifice diameter. Overall, no single metric or test condition distinguishes HFA products from CDC products, but, for individual products tested, there were a combination of metrics that differentiated one from another. ©Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.

Liu X, Doub WH, Guo C. “Assessment of the Influence Factors on Nasal Spray Droplet Velocity Using Phase-Doppler Anemometry (PDA).” AAPS PharmSciTech. 2011 Mar;12(1):337-43. doi: 10.1208/s12249-011-9594-1. Epub 2011 Feb 1. PMID: 21286880 Free PMC Article

ABSTRACT: Droplet velocity is an important parameter that can be used to characterize nasal spray products. In this study, a phase-Doppler anemometry (PDA) system was used to measure the droplet velocities of nasal sprays. A survey of seven commercial nasal spray products showed a range of droplet velocities from 6.7 to 19.2 m/s, all significantly different from each other. A three-level, four-factor Box-Behnken design of experiments (DOE) methodology were applied to investigate the influences of actuation parameters and formulation properties on nasal spray droplet velocity using a set of placebo formulations. The DOE study shows that all four input factors (stroke length, actuation velocity, concentration of the gelling agent, and concentration of the surfactant) have significant influence on droplet velocity. An optimized quadratic model generated from the DOE results describes the inherent relationships between the input factors and droplet velocity thus providing a better understanding of the input factor influences. Overall, PDA provides a new in vitro characterization method for the evaluation of inhalation drugs through assessment of spray velocity and may assist in product development to meet drug delivery equivalency requirements. ©2011 American Association of Pharmaceutical Scientists

Liu X, Doub WH, Guo C. “Evaluation of droplet velocity and size from nasal spray devices using phase Doppler anemometry (PDA).” Int J Pharm. 2010 Mar 30; 388(1-2): 82-7. doi: 10.1016/j.ijpharm.2009.12.041. Epub 2010 Jan 5. PubMed PMID: 20043981

ABSTRACT: 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. ©2009 Wiley-Liss, Inc.

Guo C, Ye W, Kauffman J, Doub WH. “Evaluation of impaction force of nasal sprays and metered-dose inhalers using the Texture Analyser.” J Pharm Sci. 2009 Aug; 98(8):2799-806. doi: 10.1002/jps.21648. PMID: 19097159

ABSTRACT: The impaction force from an inhalation product is an important characteristic 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. ©2009 Wiley-Liss, Inc.

Guo, C., K. Stine, J. Kauffman, and W. H. Doub. “Assessment of the Influence Factors on In Vitro Testing of Nasal Sprays Using Box-Behnken Experimental Design.” European Journal of Pharmaceutical Sciences, Volume 35, Issue 5, 18 December 2008, Pages 417-426

ABSTRACT: The purpose of the research was to investigate the influences of actuation parameters and formulation physical properties on nasal spray delivery performance using design of experiment (DOE) methodology. A 3-level, 4-factor Box-Behnken design with a total of 27 experimental runs was used in this study. Nine simulated aqueous formulations with different viscosities and surface tensions were prepared using carboxymethylcellulose sodium (CMC, gelling agent) and Tween80 (surfactant) each at three concentration levels. Four factors, actuation stroke length, actuation velocity, concentration of gelling agent, and concentration of surfactant were investigated for their influences on measured responses of shot weight, spray pattern, plume geometry and droplet size distribution (DSD). The models based on data from the DOE were then optimized by eliminating insignificant terms. Pfeiffer nasal spray pump units filled with the simulated formulations were used in the study. Nasal pump actuation stroke length exerts a strong, independent influence on shot weight, and also slightly affects spray pattern and plume geometry. Actuation velocity and concentration of gelling agent have significant effects on spray pattern, plume geometry and DSD, in a complicated manner through interaction terms. Concentration of surfactant has little, if any, influence on nasal spray characteristics. Results were fitted to quadratic models describing the inherent relationships between the four factors evaluated and nasal spray performance. The DOE study helped us to identify the source of variability in nasal spray product performance, and obtained better understanding in how to control the variability. Moreover, the quadratic models developed from the DOE study quantitatively describe the inherent relationships between the factors and nasal spray performance characteristics. With the assistance of the response surfaces developed from the DOE model, the time and labor in designing a nasal spray product to achieve desired product performance characteristics can be reduced. PMID: 18832029 [PubMed – indexed for MEDLINE]

Guo C, Doub WH. “The Influence of Actuation Parameters on In Vitro Testing of Nasal Spray Products.” J Pharm Sci. 2006 Sep; 95(9):2029-40. PMID: 16865693

ABSTRACT: Nasal spray drug products are normally characterized via measurement of shot weight, spray pattern, plume geometry, and droplet size distribution (DSD). In this project, the actuation parameters, such as stroke length, actuation velocity, and actuation acceleration, were investigated to ascertain how they affect nasal spray characteristics. Pfeiffer nasal spray pump units filled with water were used in the study. Actuation parameters were adjusted using an electronic automated actuation system, SprayVIEW™ NSx. Spray pattern and plume geometry measurements were carried out using a high speed optical spray characterization system, SprayVIEW™ NSP, and DSD analysis was performed using a Malvern 2600 laser diffraction system. Our results show that different actuation parameters affect the nasal spray characteristics in different ways and to different degrees. Among all the actuation parameters, stroke length and actuation velocity have significant effects on the nasal spray characteristics, while the other actuation parameters have little, if any, effect. Compared to spray pattern, plume geometry and DSD, shot weight provides very little characterization information. The findings from this work suggest that, for in vitro bioavailability (BA) and bioequivalence (BE) studies of nasal spray products, the actuation parameters, stroke length, and velocity must be carefully selected. Spray pattern, plume geometry, and DSD appear to provide critical data for assessment of nasal pump performance. ©2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:2029–2040, 2006

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