Developing Dry Powder Inhaler Formulations

This section aims to provide a concise and contemporary technical perspective and reference resource covering dry powder inhaler (DPI) formulations. While DPI products are currently the leading inhaled products in terms of sales value, a number of confounding perspectives are presented to illustrate why they are considered surprisingly, and often frustratingly, poorly understood on a fundamental scientific level, and most challenging to design from first principles. At the core of this issue is the immense complexity of fine cohesive powder systems. This review emphasizes that the difficulty of successful DPI product development should not be underestimated and is best achieved with a well-coordinated team who respect the challenges and who work in parallel on device and formulation and with an appreciation of the handling environment faced by the patient. The general different DPI formulation types, which have evolved to address the challenges of aerosolizing fine cohesive drug-containing particles to create consistent and effective DPI products, are described. This section reviews the range of particle engineering processes that may produce micron-sized drug-containing particles and their subsequent assembly as either carrier-based or carrier-free compositions. The creation of such formulations is then discussed in the context of the material, bulk, interfacial and ultimately drug-delivery properties that are considered to affect formulation performance. A brief conclusion then considers the future DPI product choices, notably the issue of technology versus affordability in the evolving inhaler market.

Development of In Vitro Evaluation System for Assessing Drug Dissolution Considering Physiological Environment in Nasal Cavity

Estimating the dissolution behavior of a solid in the nasal mucus is challenging for solid dosage forms designed for the nasal application as the solid dissolves into nasal mucus and permeates through the mucosa. In the current study, the dissolution behavior of powders in the artificial nasal fluid was investigated using a 3D-printed chamber system to establish in vitro evaluation system for the dissolution of solid formulations that can simulate the intranasal environment in vivo. The dissolution rates of the five model drugs correlated with their solubility (r2 = 0.956, p < 0.01). The permeation rate of drugs across the Calu-3 cell layers after powder application depends on the membrane permeability of the drug. An analysis of membrane permeability considering the dissolution of powders showed the possibility of characterizing whether the drug in the powder was dissolution-limited or permeation-limited. This suggests that critical information can be obtained to understand which mechanism is more effective for the improvement of drug absorption from powders. This study indicates that the elucidation of drug dissolution behavior into nasal mucus is an important factor for the formulation of nasal powders and that the in vitro system developed could be a useful tool.

An expert opinion on respiratory delivery of high dose powders for lung infections

INTRODUCTION

High dose powder inhalation is evolving as an important approach to to treat lung infections. It is important to its identify applications, consider the factors affecting high dose powder delivery, and assess the effect of high dose drugs in patients.

AREA COVERED

Both current and pipeline high dose inhalers and their applications have been summarized. Challenges and opportunities to high dose delivery have been highlighted after reviewing formulation techniques in the context of factors affecting aerosolization, devices, and patient factors.

EXPERT OPINION

High dose inhaled delivery of antimicrobials is an innovative way to increase treatment efficacy of respiratory infections, tackle drug resistance, and the scarcity of new antimicrobials. The high dose inhaled technology also has potential for systemic action; however, innovations in formulation strategies and devices are required to realize its full potential. Advances in formulation strategies include the use of excipients or the engineering of particles to decrease the cohesive property of microparticles and their packing density. Similarly, selection of a synergistic drug instead of an excipient can be considered to increase aerosolization and stability. Device development focused on improving dispersion and loading capacity is also important, and modification of existing devices for high dose delivery can also be considered.

Inhaled Delivery of Anti-Pseudomonal Phages to Tackle Respiratory Infections Caused by Superbugs

Background: Respiratory infections are increasingly difficult to treat due to the emergence of multidrug-resistant bacteria. Rediscovery and implementation of inhaled bacteriophage (phage) therapy as a standalone or supplement to antibiotic therapy is becoming recognized as a promising solution to combating respiratory infections caused by these superbugs. To ensure maximum benefit of the treatment, phages must remain stable during formulation as a liquid or powder and delivery using a nebulizer or dry powder inhaler. Methods: Pseudomonas-targeting PEV phages were used as model phages to assess the feasibility of aerosolizing biologically viable liquid formulations using commercial nebulizers in the presence and absence of inhaled antibiotics. The advantages of powder formulations were exploited by spray drying to produce inhalable powders containing PEV phages with and without the antibiotic ciprofloxacin. Results: The produced phage PEV20 and PEV20-ciprofloxacin powders remained stable over long-term storage and exhibited significant bacterial killing activities in a mouse lung infection model. Conclusion: These studies demonstrated that inhaled phage (-antibiotic) therapy has the potential to tackle respiratory infections caused by superbugs.

Combining Powder Formulations of Drugs with Food and Beverages to Improve Palatability

The taste of medicines can significantly affect patient adherence. Pediatric patients often cannot take powder medicines because of their unpleasant taste. Therefore, patients' parents and health care professionals, including pharmacists, often combine medicines with food or beverages to make them easier for pediatric patients to consume because this can reduce their unpleasant taste. The purpose of this study was to evaluate the palatability of powder formulations of azithromycin and carbocysteine and explore their combination with food or beverages to improve palatability for pediatric patients. We quantitatively evaluated the palatability of powder formulations by performing the gustatory sensation test using the visual analog scale score. The gustatory sensation tests were performed on 16 healthy adult volunteers (age 23.0 ± 2.6 years) and indicated that some food and beverages improved the palatability of the powder formulations of azithromycin and carbocysteine. The results of this study indicate that ice cream improves the palatability of azithromycin, while yogurt improves the palatability of carbocysteine. Moreover, the subjects recommended these same combinations for pediatric patients. This study suggests that some foods and beverages improve the palatability of powder formulations, thereby decreasing the possibility that pediatric patients will refuse medications because of their unpleasant taste.

[Optimization of Nasal Drug Absorption from Powder Formulations: The Feasibility of Controlling Drug Absorption by the Use of Pharmaceutical Excipients]

Nasal application of powder formulations has garnered attention because of its significant potential for systemic drug delivery. Because a powder drug must first diffuse from the formulation and dissolve in the nasal cavity fluid before transepithelial permeation, dissolution and diffusion are distinct but important factors for nasal drug absorption. Since the formulation is directly administered onto the nasal mucosal surface, the effect of excipients on drug absorption may be significant. Therefore, the influence of excipients on nasal drug absorption was evaluated. Three types of hydroxypropyl cellulose (HPC) [HPC (SL), HPC (M), and HPC (H)], lactose, and sodium chloride (NaCl) were used as excipients. Warfarin (WF), piroxicam (PXC), sumatriptan (STP), and norfloxacin (NFX) were selected as model drugs. HPC (M) enhanced the absorption of PXC, while both HPC (M) and HPC (H) enhanced the absorption of STP. All three HPCs failed to enhance the absorption of WF. An increase in the polymerization degree of HPCs decreased the diffusion of drugs in HPC solutions, but prolonged their nasal retention. Lactose and NaCl increased the fluid volume on the nasal mucosal surface by increasing the osmotic pressure, thereby enhancing the nasal absorption of PXC and NFX; however, lactose and NaCl accelerated the nasal clearance of these. These results indicate that nasal drug absorption from powder formulations can be controlled by excipients.

[Applications of Raman Spectroscopy on Quality Control of Hospital Formulations]

Hospital formulation has several advantages, including the flexibility of customization as per the disease state or the patients' precise requirements. However, compared with commercial formulations, hospital formulations are usually not under the same level of quality check. In the present study, we tested mixed powder formulations prepared in a hospital pharmacy using Raman spectroscopy to investigate the feasibility of applying Raman spectroscopy as a quality-control tool of hospital formulations. For this purpose, we first established a numerical evaluation method to determine the uniformity of a powder mixture using Raman chemical imaging data with atropine sulfate/lactose mixture samples and revealed that the mixing uniformity correlated to the experience level of the pharmacist. Next, we developed a content quantification method in a one-dose packaged powder formulation by measuring the Raman spectra from the outside of the package. Because this method allows for quantification of the components inside the package in a non-destructive and non-contact manner, it can be applied for content confirmation after one-dose packaging. Using this method, the content uniformity of the mixed powder formulation in the one-dose package was compared between the formulations prepared by the pharmacists and those prepared by a pharmacy robot. Our study indicates the possibility of applying Raman spectroscopy as a quality-control tool of hospital formulations. Studies on further applications of Raman spectroscopy in the field of clinical pharmacology are expected.