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The pulmonary fate of inhaled poorly water-soluble drugs is not entirely clear. In this study, the main objective was to investigate the in vivo inhalation biopharmaceutics in the aspects of dissolution, mucociliary clearance, absorption and tissue binding using intratracheally administered budesonide and ciclesonide suspensions as model drugs. In doing so, this study first developed a method to differentiate between dissolved and undissolved ciclesonide in the lungs for evaluating in vivo dissolution. Following deposited in rat airways, the drug particles underwent rapid dissolution and mucociliary clearance, leading to the complete removal of drugs from the airways within 2 h and a limited absorption time less than 2 h. Upon dissolution, budesonide and ciclesonide were taken up and retained in the lung tissues for up to 12 h and 24 h, respectively. The in vivo dissolution profiles in the airways exhibited the sameness as the in vitro counterparts in a 0.5% sodium dodecyl sulfate solution as indicated by the similarity factor f2. The efficacy results in a lipopolysaccharide induced lung injury model showed that the duration of local anti-inflammatory was dependent on the drug levels in the lung tissues, but not on the in vitro/in vivo dissolution and plasma pharmacokinetics. The present results demonstrated that ciclesonide suspension has the potential to achieve once-daily dosing for nebulization therapy and the in vitro dissolution profile has limited usefulness in predicting in vitro-in vivo correlation., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The main objective of this study was to test the hypothesis that inhaled nanocrystals of a highly lipophilic drug could be used as a novel approach for producing sustained pulmonary delivery. Curcumin acetate, an ester prodrug of curcumin, was utilized as a highly lipophilic model drug. Curcumin acetate was subjected to wet ball milling to produce different particle sizes of nanocrystals and microparticles, and the milled curcumin acetate was spray-dried to yield similar inhalable microparticles. Following intrapulmonary administration in rats, pharmacokinetic experiments indicated that curcumin acetate significantly extended the pulmonary absorption time by 7.2-fold compared to curcumin, possibly due to the high lipophilicity of the former. The biodistribution data showed that aerosolized curcumin acetate nanocrystals 123.7 nm in size not only prolonged pulmonary retention, with the AUC value of curcumin acetate being 7.62-fold higher than that of the microparticles 1120 nm in size, but also increased the local in vivo release rate by 3.3-fold and the local availability of converted curcumin by 25.1-fold. In addition, the improved local availability resulted in better pharmacological efficacy in a monocrotaline-induced rat model of pulmonary arterial hypertension. This study was the first to demonstrate that inhalable nanocrystals are a feasible means for the sustained pulmonary delivery of highly lipophilic drugs.

Polymeric micelles represent interesting delivery systems for pulmonary sustained release. However, little is known about their in vivo release and translocation profile after delivery to the lungs. In the present study, curcumin acetate (CA), which is an ester prodrug of curcumin, or the mixture of CA and Nile red was encapsulated into PEG–PLGA micelles by a solvent evaporation method. The micellar formulation increased the stability of CA in water and physiologically relevant fluids and led to a sustained drug release in vitro. Following intratracheal (IT) administration to rats, CA loaded micelles achieved not only prolonged pulmonary retention with AUC values almost 400-fold higher than by IV route, but also local sustained release up to 24 h. In addition, IT delivery of micelles appeared to facilitate the uptake into the pulmonary vascular endothelium and efficiently translocate across the air–blood barrier and penetrate into the brain. Co-localization of CA and Nile red confirmed that micelles in lung and brain tissue were still intact. This study is the first to demonstrate that aerosolized PEG–PLGA micelles are a promising carrier for both pulmonary and non-invasive systemic sustained release of labile drugs.