Targeting of Inhaled Therapeutics to the Small Airways: Nanoleucine Carrier Formulations

Design of dry powder inhalers to improve patient outcomes: it's not just about the device

INTRODUCTION

Up to 50% of asthma/COPD patients make critical errors in dose preparation and dose inhalation with current marketed DPIs which negatively impact clinical outcomes. Others fail to adhere to their chronic treatment regimen.

AREAS COVERED

For this review, we describe how a human-factors approach to design of a dry powder inhaler can be used to improve usability, proficiency, and functionality of DPIs, while effectively mitigating critical errors associated with DPIs. The review highlights the critical importance of utilizing improved formulations with monomodal aerodynamic particle size distributions to reduce variability associated with oropharyngeal filtering of particles, flow rate dependence, and co-formulation effects.

EXPERT OPINION

Much of the variability in dose delivery with DPIs is associated with limitations of the bimodal APSDs inherent in current lactose blend formulations. Evidence supports that improved lung targeting and dose consistency can be achieved with drug-device combination products comprising spray-dried powders. Unfortunately, no data exists to assess whether these advances observed in in vitro and in vivo dose delivery studies will translate into improved clinical outcomes. Given the significant percentage of patients that receive suboptimal drug delivery with current DPIs it would behoove the industry to assess the efficacy of new approaches.

Colistin-loaded aerosolizable particles for the treatment of bacterial respiratory infections

Compared to parenteral administration of colistin, its direct pulmonary administration can maximize lung drug deposition while reducing systemic adverse side effects and derived nephrotoxicity. Current pulmonary administration of colistin is carried out by the aerosolization of a prodrug, colistin methanesulfonate (CMS), which must be hydrolized to colistin in the lung to produce its bactericidal effect. However, this conversion is slow relative to the rate of absorption of CMS, and thus only 1.4 % (w/w) of the CMS dose is converted to colistin in the lungs of patients receiving inhaled CMS. We synthesized several aerosolizable nanoparticle carriers loaded with colistin using different techniques and selected particles with sufficient drug loading and adequate aerodynamic behavior to efficiently deliver colistin to the entire lung. Specifically, we carried out (i) the encapsulation of colistin by single emulsion-solvent evaporation with immiscible solvents using polylactic-co-glycolic (PLGA) nanoparticles; (ii) its encapsulation using nanoprecipitation with miscible solvents using poly(lactide-co-glycolide)-block-poly(ethylene glycol) as encapsulating matrix; (iii) colistin nanoprecipitation using the antisolvent precipitation method and its subsequent encapsulation within PLGA nanoparticles; and (iv) colistin encapsulation within PLGA-based microparticles using electrospraying. Nanoprecipitation of pure colistin using antisolvent precipitation showed the highest drug loading (55.0 ± 4.8 wt%) and spontaneously formed aggregates with adequate aerodynamic diameter (between 3 and 5 μm) to potentially reach the entire lung. These nanoparticles were able to completely eradicate Pseudomonas aeruginosa in an in vitro lung biofilm model at 10 µg/mL (MBC). This formulation could be a promising alternative for the treatment of pulmonary infections improving lung deposition and, therefore, the efficacy of aerosolized antibiotics.

Recent developments in the computational simulation of dry powder inhalers

This article reviews recent developments in computational modeling of dry powder inhalers (DPIs). DPIs deliver drug formulations (sometimes blended with larger carrier particles) to a patient's lungs via inhalation. Inhaler design is complicated by the need for maximum aerosolization efficiency, which is favored by high levels of turbulence near the mouthpiece, with low extrathoracic depositional loss, which requires low turbulence levels near the mouth-throat region. In this article, we review the physical processes contributing to aerosolization and subsequent dispersion and deposition. We assess the performance characteristics of DPIs using existing simulation techniques and offer a perspective on how such simulations can be improved to capture the physical processes occurring over a wide range of length- and timescales more efficiently.