Elucidation of the effect of added fines on the performance of dry powder inhalation formulations.

Dry powder inhalers (DPIs) are regularly used to treat respiratory diseases. Adding extrinsic fine excipient particles to the blend of active pharmaceutical ingredient (API) and carrier is an established strategy to improve aerosolization efficiency during pulmonary drug delivery. Different amounts and grades of lactose fines may, however, compromise the flowability and downstream processing of the material. Further, given the particle size of the inhaled fine particles (<5.5 µm), also deposition of lactose fines to different lung regions following inhalation cannot be excluded. This study aimed to investigate the impact of commercially available extrinsic lactose fine materials produced using different milling parameters, on physicochemical properties and aerosolization performance of ternary blends, as a factor of time and storage conditions. Further, for the first time, it was attempted to elucidate the effect that the amount of present fines has on the dissolution of the model API from the ternary blends exposed to different storage conditions. We showed that rheological behavior was impacted when a higher amount of fines was present, and this effect was further enhanced by storage at high relative humidity. The aerosolization efficiency was vastly improved with increasing content of fines. Still, initial data indicated that the dissolution of the poorly soluble API was retarded when more fines were present in blends.

Impact of simulated lung fluid components on the solubility of inhaled drugs and predicted in vivo performance.

Orally inhaled products (OIPs) are gaining increased attention, as pulmonary delivery is a preferred route for the treatment of various diseases. Yet, the field of inhalation biopharmaceutics is still in development phase. For a successful correlation between various in vitro data obtained during formulation characterization and in vivo performance, it is necessary to understand the impact of parameters such as solubility and dissolution of drugs. In this work, we used in vitro-in silico feedback-feedforward approach to gain a better insight into the biopharmaceutics behavior of inhaled Salbutamol Sulphate (SS) and Budesonide (BUD). The thorough characterization of the in vitro test media and the impact of different in vitro fluid components such as lipids and protein on the solubility of aforementioned drugs was studied. These results were subsequently used as an input into the developed in silico models to investigate potential PK parameter changes in vivo. Results revealed that media comprising lipids and albumin were the most biorelevant and impacted the solubility of BUD the most. On the contrary, no notable impact was seen in case of SS. The use of simple media such as phosphate buffer saline (PBS) might be sufficient to use in solubility studies of the highly soluble and permeable drugs. However, its use for the poorly soluble drugs is limited due to the greater potential for interactions within in vivo environment. The use of in silico tools showed that the model response varies, depending on the used media. Therefore, this work highlights the relevance of carefully selecting the media composition when investigating solubility and dissolution behavior, especially in the early phases of drug development and of poorly soluble drugs.

Use of PBPK Modeling To Evaluate the Performance of Dissolv It, a Biorelevant Dissolution Assay for Orally Inhaled Drug Products.

The dissolution of inhaled drug particles in the lungs is a challenge to model using biorelevant methods in terms of (i) collecting a respirable emitted aerosol fraction and dose, (ii) presenting this to a small volume of medium that is representative of lung lining fluid, and (iii) measuring the low concentrations of drug released. We report developments in methodology for each of these steps and utilize mechanistic in silico modeling to evaluate the in vitro dissolution profiles in the context of plasma concentration-time profiles. The PreciseInhale aerosol delivery system was used to deliver Flixotide aerosol particles to Dissolv It apparatus for measurement of dissolution. Different media were used in the Dissolv It chamber to investigate their effect on dissolution profiles, these were (i) 1.5% poly(ethylene oxide) with 0.4% l-alphaphosphatidyl choline, (ii) Survanta, and (iii) a synthetic simulated lung lining fluid (SLF) based on human lung fluid composition. For fluticasone proprionate (FP) quantification, solid phase extraction was used for sample preparation with LC-MS/MS analysis to provide an assay that was fit for purpose with a limit of quantification for FP of 312 pg/mL. FP concentration-time profiles in the flow-past perfusate were similar irrespective of the medium used in the Dissolv It chamber (∼0.04-0.07%/min), but these were significantly lower than transfer of drug from air-to-perfusate in isolated perfused lungs (0.12%/min). This difference was attributed to the Dissolv It system representing slower dissolution in the central region of the lungs (which feature nonsink conditions) compared to the peripheral regions that are represented in the isolated lung preparation. Pharmacokinetic parameters ( Cmax, Tmax, and AUC0-∞) were estimated from the profiles for dissolution in the different lung fluid simulants and were predicted by the simulation within 2-fold of the values reported for inhaled FP (1000 µg dose) administered via Flixotide Evohaler 250 µg strength inhaler in man. In conclusion, we report methods for performing biorelevant dissolution studies for orally inhaled products and illustrate how they can provide inputs parameters for physiologically based pharmacokinetic (PBPK) modeling of inhaled medicines.

Searching for physiologically relevant in vitro dissolution techniques for orally inhaled drugs.

Inhalation is the preferred route for the treatment of lung diseases. More recently, also formulations for systemic treatment have been developed. For efficient development of inhalation products it is necessary to identify a link between particle parameters and in vivo performance. Such a relation exists for oral drugs where dissolution and permeation across Caco-2 monolayers are correlated to in vivo absorption. By contrast, the only in vitro parameter with established link to absorption for inhalation is particle size. In vitro dissolution could be another important parameter because low solubility determines bioavailability of inhaled drugs. The review highlights the importance of dissolution for drug availability in general and lists important differences in dissolution testing of oral and inhaled formulations. Dissolution testing protocols are summarized with focus on the composition of the various fluids, which are used to mimic particle dissolution in the deep lung. Finally, a role of in silico modelling in identification of physiologically relevant dissolution fluids and in in vitro in vivo correlation is suggested.

How does secondary processing affect the physicochemical properties of inhalable salbutamol sulphate particles? A temporal investigation.

As pulmonary drug delivery is extended from low doses to high doses, physicochemical characteristics of the active pharmaceutical ingredient gain importance in the development of dry powder inhalers. Therefore, the present work aims to understand the impact of distinct engineering techniques on the process induced physicochemical characteristics of salbutamol sulphate particles over time. The particle engineering techniques chosen were jet-milling and spray-drying, two well used processes in the production of predominately crystalline and amorphous inhalable particles, respectively. Fourier transform infrared spectroscopy, modulated differential scanning calorimetry, particle size distribution and tensiometry experiments were used to characterise the engineered powders immediately, 7, 14 and 21 days after production. The rugged spherical amorphous particles (3.75±0.08µm) obtained via spray-drying showed that they were capable of forming strong agglomerates (5.01±0.22µm) through "amorphous bridging". On the other hand, jet-milling produced smaller (2.06±0.08µm), crystalline, irregular shaped particles with a very large surface area (11.04±0.10m2/g) that, over time, formed looser particle aggregates of decreasing size (3.76±0.10µm). Temporal evolution of the properties of spray-dried and jet milled particles showed a notable influence on the efficiency of blending with a model carrier at 0, 7 and 21 days (e.g. relative standard deviation of drug content of 11.3, 7.0 and 21.6%, respectively).