Evaluation and modification of commercial dry powder inhalers for the aerosolization of a submicrometer excipient enhanced growth (EEG) formulation

Abstract

The aim of this study was to evaluate and modify commercial dry powder inhalers (DPIs) for the aerosolization of a submicrometer excipient enhanced growth (EEG) formulation. The optimized device and formulation combination was then tested in a realistic in vitro mouth-throat – tracheobronchial (MT–TB) model. An optimized EEG submicrometer powder formulation, consisting of albuterol sulfate (drug), mannitol (hygroscopic excipient), l-leucine (dispersion enhancer) and poloxamer 188 (surfactant) in a ratio of 30:48:20:2 was prepared using a Büchi Nano spray dryer. The aerosolization performance of the EEG formulation was evaluated with five conventional DPIs: Aerolizer, Novolizer, HandiHaler, Exubera and Spiros. To improve powder dispersion, the HandiHaler was modified with novel mouth piece (MP) designs. The aerosol performance of each device was assessed using a next generation impactor (NGI) at airflow rates generating a pressure drop of 4kPa across the DPI. In silico and in vitro deposition and hygroscopic growth of formulations was studied using a MT–TB airway geometry model. Both HandiHaler and Aerolizer produced high emitted doses (EDs) together with a significant submicrometer aerosol fraction. A modified HandiHaler with a MP including a three-dimensional (3D) array of rods (HH-3D) produced a submicrometer particle fraction of 38.8% with a conventional fine particle fraction (%<5μm) of 97.3%. The mass median diameter (MMD) of the aerosol was reduced below 1μm using this HH-3D DPI. The aerosol generated from the modified HandiHaler increased to micrometer size (2.8μm) suitable for pulmonary deposition, when exposed to simulated respiratory conditions, with negligible mouth–throat (MT) deposition (2.6%).