Research Paper Applicability of an Ultrasonic Nebulization System for the Airways Delivery of Beclomethasone Dipropionate in a Murine Model of Asthma Bos ˇka Hrvac ˇic ´, 1,3 Berislav Bos ˇnjak, 1 Marijan Tudja, 2 Milan Mesic ´, 1 and Mladen Merc ´ep 1 Received June 6, 2005; accepted April 7, 2006 Purpose. We have assessed the use of an ultrasonic nebulization system (UNS), composed of ultrasonic nebulizer and diffusion dryer filled with charcoal, for the effective delivery of beclomethasone to the airways in a murine asthma model. Methods. Solution of beclomethasone in ethanol was aerosolized using an ultrasonic nebulizer. Passage of the aerosol through a drying column containing charcoal and deionizer produced dry beclomethasone particles. Particles were delivered to BALB/c mice placed in a whole-body exposition chamber 1 h before intranasal challenge with ovalbumine. Efficacy of beclomethasone delivery was evaluated by examining bronchoalveolar lavage fluid (BALF) cytology. Results. Effect of three UNS system parameters on aerosol particle size was investigated. The critical parameter affecting the size of dry particles was beclomethasone concentration in aerosolized solution and solution flow rate while power level of ultrasonic nebulizer generator had no effect. Administration of beclomethasone at calculated dose of 150 mg/kg to mice significantly decreased total cell number and relative eosinophil number in BALF. Conclusions. The UNS system produces a monodisperse aerosol that can be used for inhalative delivery of poorly water soluble substances to experimental animals. The UNS system minimizes formulation requirements and allows rapid and relatively simple efficacy and toxicity testing in animals. KEY WORDS: asthma; beclomethasone dipropionate; dry powder; inhalation delivery; mice; ultrasonic nebulization system. INTRODUCTION Asthma and chronic obstructive pulmonary disease (COPD) are among the most common chronic diseases and the prevalence of both diseases is increasing. It is estimated that asthma and COPD each affects approximately 4 to 10% of the population (1Y4) and they represent an important pharmacoeconomic burden to society. In the treatment of asthma and COPD, as well as other pulmonary disorders, localized delivery of drugs to the respiratory tract is an important and effective therapeutic method. Inhalation delivery for the treatment of lung disorders has the clinical advantages over systemic therapy since it requires relatively small doses for effective therapy, minimizes possible side effects, and facilitates delivery of macromolecules that are poorly absorbed from the gastrointestinal tract (5,6). Inhala- tion delivery is dependent on dispersion of solid and liquid particles suspended in gas, i.e., aerosol generation. In human medicine, systems used for drug delivery by inhalation include pressurized metered-dose inhalers (pMDI), dry powder inhalers (DPI), and jet pneumatic or ultrasonic nebulizers, as well as recently developed small volume liquid inhalers (7Y9). pMDI was the most frequently prescribed aerosol delivery system because they were effec- tive and convenient for a large proportion of patients (10). However, the most widely used propellants for pMDI operation, chlorofluorocarbons, were prohibited in the year 2000 by the Montreal Protocol. Although new pMDIs that use environmentally benign propellants have been devel- oped, alternative devices, such as DPI and ultrasonic nebulizers, have gained in popularity. DPI are breath- activated inhalers that rely on the patient’s inspiratory flow to deliver the micronized drug particles to the respiratory tract (10). Dry powder generation is often hindered by aggregation of drug particles, which is exacerbated by the electrostatic charge of micronized particles and the hygro- scopic nature of the drug (10). In contrast to DPI, nebulizers produce aerosols from drug solutions. Ultrasonic nebulizers utilize conversion of high frequency electrical pulses to mechanical vibrations which then convert liquid into a fine mist (11). In comparison to pMDI and DPI, nebulizers offer several advantages: they produce narrow-sized particles that enable uniform delivery of drug into the small airways. 1765 0724-8741/06/0800-1765/0 # 2006 Springer Science + Business Media, Inc. Pharmaceutical Research, Vol. 23, No. 8, August 2006 ( # 2006 ) DOI: 10.1007/s11095-006-9029-y 1 PLIVA Research Institute Ltd., Prilaz baruna Filipovic ´a 29, HR- 10000, Zagreb, Croatia. 2 PLIVA Croatia Ltd., Zagreb, Croatia. 3 To whom correspondence should be addressed. (e-mail:boska. hrvacic@pliva.hr) ABBREVIATIONS: BALF, bronchoalveolar lavage fluid; beclomethasone, beclomethasone dipropionate; COPD, chronic obstructive pulmonary disease; DPI, dry powder inhaler; FPF(<2.20 mm), fine particle fraction <2.20 mm aerodynamic diameter; GSD, geometric standard deviation; pMDI, pressurized metered-dose inhaler; SD, standard deviation; UNS, ultrasonic nebulization system.