The forgotten material: Highly dispersible and swellable gelatin-based microspheres for pulmonary drug delivery of cromolyn sodium and ipratropium bromide

Controlled-release formulations for pulmonary delivery are highly desirable for treating chronic diseases such as COPD. However, a limited number of polymers are currently approved for inhalation. The study presents a promising strategy using gelatin as a matrix for inhalable dry powders, allowing the controlled release of ionic drugs. Ionized cromoglicate sodium (CS) and ipratropium bromide (IBr) interacted in solution with charged gelatin before spray drying (SD). Calcium carbonate was used as a crosslinker. The microspheres showed remarkable aerosol performance after optimizing the SD parameters and did not cause cytotoxicity in A549 cells. The microspheres were highly dispersible with ∼ 50-60% of respirable fraction and fine particle fraction 55-70%. Uncrosslinked microspheres increased their size from four to ten times by swelling after 5 min showing potential as a strategy to avoid macrophage clearance and prolong the therapeutic effect of the drug. Crosslinkers prevented particle swelling. Ionic interaction generated a moderate reduction of the drug release. Overall, this study provides a novel approach for developing DPI formulations for treating chronic respiratory diseases using a biopolymer approved by the FDA, potentially enhancing drug activity through controlled release and avoiding macrophage clearance.

Advancements in the Design and Development of Dry Powder Inhalers and Potential Implications for Generic Development

Dry powder inhalers (DPIs) are drug-device combination products where the complexity of the formulation, its interaction with the device, and input from users play important roles in the drug delivery. As the landscape of DPI products advances with new powder formulations and novel device designs, understanding how these advancements impact performance can aid in developing generics that are therapeutically equivalent to the reference listed drug (RLD) products. This review details the current understanding of the formulation and device related principles driving DPI performance, past and present research efforts to characterize these performance factors, and the implications that advances in formulation and device design may present for evaluating bioequivalence (BE) for generic development.

Pinto J, Paudel A. Understanding Carrier Performance in Low-Dose Dry Powder Inhalation: An In Vitro-In Silico Approach

The use of physiologically based pharmacokinetic (PBPK) models to support drug product development has become increasingly popular. The in vitro characterization of the materials of the formulation provides valuable descriptors for the in silico prediction of the drug’s pharmacokinetic profile. Thus, the application of an in vitro–in silico framework can be decisive towards the prediction of the in vivo performance of a new medicine. By applying such an approach, this work aimed to derive mechanistic based insights into the potential impact of carrier particles and powder bulk properties on the in vivo performance of a lactose-based dry powder inhaler (DPI). For this, a PBPK model was developed using salbutamol sulphate (SS) as a model drug and the in vitro performance of its low-dose blends (2% w/w) with different types of lactose particles was investigated using different DPI types (capsule versus reservoir) at distinct airflows. Likewise, the influence of various carrier’s particle and bulk properties, device type and airflow were investigated in silico. Results showed that for the capsule-based device, low-dose blends of SS had a better performance, when smaller carrier particles (Dv_0.5 ≈ 50 μm) with about 10% of fines were used. This resulted in a better predicted bioavailability of the drug for all the tested airflows. For the reservoir type DPI, the mean particle size (Dv_0.5) was identified as the critical parameter impacting performance. Shear cell and air permeability or compressibility measurements, particle size distribution by pressure titration and the tensile strength of the selected lactose carrier powders were found useful to generate descriptors that could anticipate the potential in vivo performance of the tested DPI blends.

Evaluation of the Physico-mechanical Properties and Electrostatic Charging Behavior of Different Capsule Types for Inhalation Under Distinct Environmental Conditions

Capsule-based dry powder inhaler (DPI) products can be influenced by a multitude of interacting factors, including electrostatic charging. Tribo-charging is a process of charge transfer impacted by various factors, i.e., material surface characteristics, mechanical properties, processing parameters and environmental conditions. Consequently, this work aimed to assess how the charging behavior of capsules intended for inhalation might be influenced by environmental conditions. Capsules having different chemical compositions (gelatin and hydroxypropyl methylcellulose (HPMC)) and distinct inherent characteristics from manufacturing (thermally and cold-gelled) were exposed to various environmental conditions (11%, 22% and 51% RH). Their resulting properties were characterized and tribo-charging behavior was measured against stainless steel and PVC. It was observed that all capsule materials tended to charge to a higher extent when in contact with PVC. The tribo-charging of the thermally gelled HPMC capsules (Vcaps^® Plus) was more similar to the gelatin capsules (Quali-G™-I) than to their HPMC cold-gelled counterparts (Quali-V^®-I). The sorption of water by the capsules at different relative humidities notably impacted their properties and tribo-charging behavior. Different interactions between the tested materials and water molecules were identified and are proposed to be the driver of distinct charging behaviors. Finally, we showed that depending on the capsule types, distinct environmental conditions are necessary to mitigate charging and assure optimal behavior of the capsules.

Effect of Particle Formation Process on Characteristics and Aerosol Performance of Respirable Protein Powders

Pulmonary delivery of biopharmaceuticals may enable targeted local therapeutic effect and noninvasive systemic administration. Dry powder inhaler (DPI) delivery is an established patient-friendly approach for delivering large molecules to the lungs; however, the complexities of balancing protein stability with aerosol performance require that the design space of biopharmaceutical DPI formulations is rigorously explored. Utilizing four rationally selected formulations obtained using identical atomization conditions, an extensive study of the effect of the particle formation process (spray drying or spray freeze-drying) on powder properties, aerosol performance, and protein stability was performed. Multiple linear regression analysis was used to understand the relationship between powder properties, device dispersion mechanism, and aerosol performance. Spray drying and spray freeze-drying, despite the same spraying conditions, produced powders with vastly different physical characteristics, though similar aerosol performance. The resulting regression model points to the significance of particle size, density, and surface properties on the resulting aerosol performance, with these factors weighing differently according to the device dispersion mechanism utilized (shear-based or impaction-based). The physical properties of the produced spray dried and spray freeze-dried powders have differing implications for long-term stability, which will be explored extensively in a future study.

Dosing considerations for inhaled biologics

The number of biologics in the therapeutic development pipeline is increasing including those delivered though inhalation (Morales, 2017; Fathe, 2016). Biologics comprise a broad variety of complex macromolecules with unique physicochemical characteristics. These distinctive characteristics control their pharmacological mechanisms of action, stability, and ultimately affect their processing, formulation, and delivery requirements. This review systematically covers crucial aspects of biologic powders formulations and dry powder inhalers which need to be taken into consideration to establish the drug loading and the payload to be delivered to reach the desired clinical dose.

Formulation techniques for high dose dry powders

Delivery of drugs to the lungs via dry powder inhaler (DPI) is a promising approach for the treatment of both local pulmonary conditions and systemic diseases. Though DPIs are widely used for the pulmonary deposition of potent bronchodilators, anticholinergics, and corticosteroids, there is growing interest in the utilization of this delivery system for the administration of high drug doses to the lungs, as made evident by recent regulatory approvals for anti-microbial, anti-viral and osmotic agents. However, the formulation of high dose DPIs carries several challenges from both a physiological and physicochemical standpoint. This review describes the various formulation techniques utilized to overcome the barriers associated with the pulmonary delivery of high dose powders.

Formulation considerations for dry powder inhalers

The market for inhalable dry powder medication has consistently grown over past years. Targeting the lungs has been recognized to offer several advantages compared with oral application of drugs. The successive development of inhalation products has led to advances in local treatment of different respiratory diseases, but has also demonstrated the possibility to utilize the lungs for systemic drug delivery. Since a dry powder inhalation product is always a combination of drug formulation and inhalation device, the requirements for the development of such a system may be particularly complex. Therefore, this review aims to give an overview of the necessary considerations for a successful dry powder inhaler development.

Dry-powder inhalers in acute asthma

An updated literature search was performed to evaluate the efficacy of rapid-acting β2-agonists delivered via dry powder inhalers in the treatment of moderate-to-severe acute asthma. Databases were searched from 1985 up to December 2012. A total of 23 randomized, double-blind or open clinical studies in acute asthma comparing the efficacy of a dry powder inhaler with a pressurized metered-dose inhaler or a nebulizer, and performed under controlled hospital conditions, were identified. This review found that administration of β2-agonist bronchodilators via dry powder inhalers (formoterol, salbutamol, terbutaline and budesonide/formoterol) was effective during severe asthma worsening and acute asthma attacks, and was as effective as established therapies with a pressurized metered-dose inhaler with or without a spacer, or nebulization. These results ensure that patients can rely upon dry powder inhalers equally well as other inhaler devices during episodes of asthma worsening.

Effect of carrier gas properties on aerosol distribution in a CT-based human airway numerical model

The effect of carrier gas properties on particle transport in the human lung is investigated numerically in an imaging based airway model. The airway model consists of multi-detector row computed tomography (MDCT)-based upper and intra-thoracic central airways. The large-eddy simulation technique is adopted for simulation of transitional and turbulent flows. The image-registration-derived boundary condition is employed to match regional ventilation of the whole lung. Four different carrier gases of helium (He), a helium-oxygen mixture (He-O(2)), air, and a xenon-oxygen mixture (Xe-O(2)) are considered. A steady inspiratory flow rate of 342 mL/s is imposed at the mouthpiece inlet to mimic aerosol delivery on inspiration, resulting in the Reynolds number at the trachea of Re( t ) ≈ 190, 460, 1300, and 2800 for the respective gases of He, He-O(2), air, and Xe-O(2). Thus, the flow for the He case is laminar, transitional for He-O(2), and turbulent for air and Xe-O(2). The instantaneous and time-averaged flow fields and the laminar/transitional/turbulent characteristics resulting from the four gases are discussed. With increasing Re( t ), the high-speed jet formed at the glottal constriction is more dispersed around the peripheral region of the jet and its length becomes shorter. In the laminar flow the distribution of 2.5-μm particles in the central airways depends on the particle release location at the mouthpiece inlet, whereas in the turbulent flow the particles are well mixed before reaching the first bifurcation and their distribution is strongly correlated with regional ventilation.