Crystalline Salbutamol sulphate (SS) is a common β2-agonist used in dry powder inhalers for the treatment of asthma. The solid-state characteristics of SS are import since they govern the stability and thus efficacy of the drug when incorporated into an inhalation medicine. Previous studies have investigated the thermal properties of SS and the complex array of thermal events have been attributed a mixture of melting and/or degradation mechanisms. In order to ascertain the exact thermal transformation processes that SS undergoes we utilised a combination of differential scanning calorimetry coupled with quadrupole mass spectrometry and thermogravimetric analysis coupled with Fourier transform infrared spectroscopy over the temperature range 25–500 °C. Based on the coupled thermal analysis data we proposed that SS undergoes a multi-step degradation mechanism in which the molecule dehydrates loosing water initially, followed by the break up of the secondary amine group and lastly formation of sulphur dioxide. When used in conjunction, the analytical techniques offered significant advantages over the use of thermal analysis alone, offering a better understanding of the transformations occurring to SS following heating.

Endotracheal intubation is commonly associated with hospital-acquired infections as the intubation device acts as reservoir for bacterial colonization in lungs. To reduce the incidence of bacterial colonization on the tubes, hydrogel coatings loaded with antimicrobial agents are gaining popularity. The aim of this study is to incorporate silver nanoparticles (AgNPs) into polyvinyl alcohol (PVA) to form stable hydrogels. Embedding AgNPs into PVA resulted in a decreased elongation at break and an increased tensile strength compared to PVA alone. Ag release profile varied as a function of the degree of hydrolysis of PVA: the higher degree of hydrolysis demonstrated a lower release rate. Fourier infrared transform spectroscopy demonstrated that AgNPs interacted exclusively with the –OH groups of PVA. AgNPs loaded PVA were non-toxic against human normal bronchial epithelial cells while effective against the attachment of Pseudomonas aeruginosa and Staphylococcus aureus with a greater effect on P. aeruginosa.

During the process of inhalable formulation drug development a deep knowledge of the physicochemical characteristics of the drug and formulation components and their relationship with the biological properties of the airways is necessary. 
For example, the solubility and lipophilicity of a drug may affect therapeutic efficacy by changing the residence time of the inhaled microparticles at the airways surface. Furthermore, the properties of aerosol drug particles, such as shape, size and density, as well as the diseases of the respiratory tract, delivery device and inhalation manoeuvre will have an impact on where these microparticles are deposited.

The airway epithelium is involved in the pathogenesis and treatment of several respiratory diseases. Epithelial cells are directly exposed to the environment and respond to xenobiotics such as medical therapies. In some cases the epithelial cells are the site of action for drug molecules or the drug molecules might need to be transported across the epithelium to arrive at the site of action (β2-agonists are transported across the epithelium to target underlying smooth muscle cells). The drug particles, which are deposited on the respiratory epithelia, have to interact with the mucus lining, dissolve and get transported through this layer. Despite advances in in vitro testing of respiratory epithelial permeability, there is little known about how and where drugs are absorbed at a cellular level and how long they reside in the lung. Therefore, pulmonary permeability assessment of drug particles, and the influence of formulation parameters on drug uptake at the epithelia, may provide insights that will allow formulations to be developed with optimised therapeutic outcomes.
This review focuses on the integration of these physicochemical characteristics with the biological factors to provide a better understanding of the fate of drug microparticles after deposition on the epithelial cells

Abstract - Purpose: Non-volatile agents such as glycerol are being introduced into solution-based pMDI formulations in order to control mean precipitant droplet size. To assess their biopharmaceutical efficacy, both microscopic and macroscopic characteristics of the plume must be known, including the effects of external factors such as the flow generated by the patient’s inhalation. We test the hypothesis that the macroscopic properties (e.g. spray geometry) of a pMDI spray can be predicted using a self-similarity model, avoiding the need for repeated testing.
Methods: Glycerol-containing and glycerol-free pMDI formulations with matched mass median aerodynamic diameters are investigated. High-speed schlieren imag- ing is used to extract time-resolved velocity, penetration and spreading angle mea- surements of the pMDI spray plume. The experimental data are used to validate the analytical model.
Results: The pMDI spray develops in a manner characteristic of a fully- developed steady turbulent jet, supporting the hypothesis. Equivalent glycerol- containing and non glycerol-containing formulations exhibit similar non-dimensional growth rates and follow a self-similar scaling behaviour over a range of physiolog- ically relevant co-flow rates.

Simvastatin (SV), a drug of the statin class currently used orally as anti- cholesterolemic, has been found not only to reduce cholesterol but also to have several other pharmacological actions that might be beneficial in airway inflammatory diseases. Currently, there is no inhalable formulation that could deliver SV to the lung. In this study a pressurised metered dose inhaler (pMDI) solution formulation of SV was manufactured, with ethanol as co-solvent, and its aerosol performance and physio- chemical properties investigated. A pMDI solution formulation containing SV and 6 %w/w ethanol was prepared. This formulation was assessed visually for SV solubility. Furthermore, the aerosols performance (using Andersen Cascade impactor at 28.3L/min) and active ingredient chemical stability up to 6 months at different storage temperatures, 4 and 25°C, was also evaluated. The physico-chemical properties of the SV solution pMDI were also characterised by differential scanning calorimetry (DSC), thermogravimetric analyses (TGA) and laser diffraction. The aerosol particles, determined using Scanning Electron Microscopy (SEM), presented smooth surface morphology and were spherical in shape. The aerosol produced had a fine particle fraction of 30.77 ± 2.44 % and a particle size distribution suitable for inhalation drug delivery. Furthermore, the short-term chemical stability showed the formulation to be stable at 4°C for up to 6 months while at 25°C, the formulation was stable up to 3 months. In this study a respirable and stable SV solution pMDI formulation for inhalation has been presented that could potentially used clinically as anti-inflammatory therapeutic for the treatment of several lung diseases.

A series of co-engineered macrolide-mannitol particles were successfully prepared using azithromycin (AZ) as a model drug. The formulation was designed to target local inflammation and bacterial colonisation, via the macrolide component, while the mannitol acted as mucolytic and taste-masking agent. The engineered particles were evaluated in terms of their physico-chemical properties and aerosol performance when delivered via a novel high-payload dry powder Orbital™ inhaler device that operates via multiple inhalation manoeuvres. All formulations prepared were of suitable size for inhalation drug delivery and contained a mixture of amorphous AZ with crystalline mannitol. A co-spray dried formulation containing 200 mg of 50:50 w/w AZ:mannitol had a 57.6% ± 7.6%  delivery efficiency with the fine particle fraction (≤ 6.8 µm)  of the emitted aerosol cloud being 80.4% ± 1.1%, with minimal throat deposition (5.3 ±0.9%) Subsequently, it can be concluded that the use of this device in combination with the co-engineered macrolide-mannitol therapy may provide a means of treating bronchiectasis.

Recent murine studies found that rifapentine, dosed daily, at least halved tuberculosis treatment times compared to standard rifampicin and isoniazid-containing regimens. However, in humans, an inhalable form of rifapentine may be necessary to considerably shorten treatment duration due to physiological barriers associated with oral therapy. The current study compares two inhalable rifapentine dry powders – a novel pure crystalline form and an amorphous form – by a series of in vitro tests. The crystalline and amorphous powders had a mass median aerodynamic size of 1.68 ± 0.03 and 1.92 ± 0.01 µm, respectively, associated with a fine particle fraction of 83.2 ± 1.2 and 68.8 ± 2.1%, respectively. A quinone degradation product was identified in the amorphous powder stored for 1 month whilst the crystalline form remained chemically stable after storage at both 0% and 60% RH, 25 ᵒC, for at least 3 months. Rifapentine was well-tolerated by pulmonary tissue and macrophage cells up to approximately 50 µM. The accumulation of rifapentine within alveolar macrophage cells was significantly higher than for rifampicin, indicating enhanced delivery to infected macrophages. The novel inhalable crystalline form of rifapentine is suitable for targeted treatment of tuberculosis infection and may radically shorten treatment duration.

This study focuses on the co-engineering of salbutamol sulphate (SS), a common bronchodilator and mannitol (MA), a mucolytic, as a potential combination therapy for mucus hypersecretion. This combination was chosen to have a synergic effect on the airways: the SS will act on the β2-receptor for relaxation of smooth muscle and enhancement of ciliary beat frequency, while mannitol will improve the fluidity of mucus, consequently enhancing its clearance from the lung. A series of co-spray dried samples, containing therapeutically relevant doses of SS and MA were prepared. The physico-chemical characteristics of the formulations were evaluated in terms of size distribution, morphology, thermal and moisture response and aerosol performance. Additionally the formulations were evaluated for their effects on cell viability and transport across an air interface Calu-3 bronchial epithelial cells, contractibility effects on bronchial smooth muscle cells and cilia beat activity using ciliated nasal epithelial cells in vitro. The formulations demonstrated size distribution and aerosol performance suitable for inhalation therapy. Transport studies revealed that the MA component of the formulation enhanced penetration of SS across the complex mucus layer and the lung epithelia cells. Furthermore, the formulation in the ratios of SS 10-6 and MA 10-3 M gave a significant increase in cilia beat frequency, while simultaneously preventing smooth muscle contraction associated with mannitol administration. These studies have established that co-spray dried combination formulations of MA and SS can be successfully prepared with limited toxicity, good aerosol performance and ability to increase the ciliary beat frequency for improving the mucociliary clearance in patients suffering form hyper secretory diseases, whilst simultaneously acting on the underlying smooth muscle.

Purpose: The purpose of this study was to present a modified Andersen cascade impactor (ACI) as a platform to evaluate the deposition and subsequent transport of aerosol micropaticles across airway epithelial cells.
Methods: The impaction plate of an ACI was modified to accommodate up to eight Snapwells. Aerodynamic particle size distribution of the modified ACI was investigated with two commercially available formulations of Ventolin® (salbutamol sulphate) and QVAR® (beclomethasone dipropionate). Deposition and transport of these drug micropaticles across sub-bronchial epithelial Calu-3 cells were also studied.
Results: The modified ACI demonstrated reproducible deposition patterns of the commercially available pressurised metered dose inhalers compared to the standard ACI. Furthermore, the Calu-3 cells could be placed in different stages of the modified ACI. No significant effect was observed among the transport rate of different particle sizes deposited on Calu-3 cells within the range of 3.3 to 0.4 μm.
Conclusions:
The use of the cell compatible ACI to assess the fate of microparticles after deposition on the respiratory epithelia may allow for better understanding of deposited microparticles in vivo

Introduction: Tuberculosis remains rampant throughout the world, in large part due to the lengthy treatment times of current therapeutic options. Rifapentine, a rifamycin antibiotic, is currently approved for intermittent dosing in the treatment of tuberculosis. Recent animal studies have shown that more frequent administration of rifapentine could shorten treatment times, for both latent and active tuberculosis infection. However, these results were not replicated in a subsequent human clinical trial.

Areas covered: This review analyses the evidence for more frequent administration of rifapentine and the reasons for the apparent lack of efficacy in shortening treatment times in human patients. Inhaled delivery is discussed as a potential option to achieve the therapeutic effect of rifapentine by overcoming the barriers associated with oral administration of this drug. Potential options for developing an inhalable form of rifapentine are also presented.

Expert opinion: Rifapentine is a promising active pharmaceutical ingredient with potential to accelerate treatment of tuberculosis if delivered by inhaled administration. Progression of current fundamental work on inhaled anti-tubercular therapies to human clinical trials is essential for determining their role in future treatment regimens. Whilst the ultimate goal for global tuberculosis control is a vaccine, a short and effective treatment option is equally crucial.

The production of high quality graphical figures of scientific data is an important aspect of medical writing, since the significance of research findings can be lost to the audience if data is presented poorly or inaccurately. This review highlights the various requirements that a writer may encounter when preparing data in a graphical format for presentation and gives an overview of 15 graphing software packages that are available on a number of platforms.

The purpose of this work was to evaluate gas perfusion isothermal calorimetry (ITC) as a method to characterize the physicochemical changes of active pharmaceutical ingredients (APIs) intended to be formulated in pressurised metered dose inhalers (pMDIs) after exposure to a model propellant. Spray dried samples of beclomethasone dipropionate (BDP) and salbutamol sulphate (SS) were exposed to controlled quantities of 2H,3H-decafluoropentane (HPFP) to determine whether ITC could be used as a suitable analytical method for gathering data on the behavioural properties of the powders in real time. The crystallization kinetics of BDP and the physiochemical properties of SS were successfully characterized using ITC and supported by a variety of other analytical techniques. Correlations between real and model propellant systems were also established using hydrofluoroalkane (HFA-227) propellant. In summary, ITC was found to be suitable for gathering data on the crystallization kinetics of BDP and SS. In a wider context, this work will have implications on the use of ITC for stability testing of APIs in HFA-based pMDIs.

The aerosol performance, physical properties and formation process of two corticosteroids (beclomethasone dipropionate and fluticasone propionate) and caffeine (active pharmaceutical ingredients: APIs) from ethanol-based pressurized metered dose inhaler solution formulations, containing various ethanol fractions, were evaluated using cascade impaction, thermal analysis and scanning electron microscopy. In general, the final aerosol particle size distribution (post USP induction port) was unaffected by ethanol concentration (mass median aerodynamic diameter and geometric standard deviation values for each formulation were independent of ethanol % (w/w) in the initial formulation). However, ethanol concentration directly affected the percentage of particles that passed the USP induction, resulting in a significant decrease in fine particle fraction, across all formulations, as ethanol was increased. Thus it can be concluded that particle size is governed by initial droplet diameter and API concentration, while performance is governed by drying time. The physico-chemical properties and morphology of the dried API particles, collected from cascade impactor stages, showed that the solid state was related to the glass transition temperature (Tg) and, to some extent, the saturated hydrofluoroalkane propellant (HFA)/ethanol solubility of the APIs. The low Tg API caffeine, with high HFA solubility resulted in crystalline particles, while the high Tg corticosteroids were amorphous. Furthermore, the final structure of the particles was dependent on the ethanol concentration and drying kinetics after initial droplet formation. This study has shown that the solid-state physico-chemical properties and morphology of particles is intrinsically linked to the API properties and drying kinetics of the propellant/co-solvent. These variations in aerosol efficiency, particle morphology and solid-state characteristics may have direct effects on drug efficacy and bioavailability after deposition in the lung.

Purpose: To investigate the influence of different actuator materials and nozzle designs on the electrostatic charge properties of a series of solution metered dose inhaler (pMDI) aerosols.

Methods: Actuators are manufactured with two different nozzle designs (flat and cone) using five different materials selected from the triboelectric series (Nylon, Polyethylene terephthalate, Polyethylene – High density, Polypropylene copolymer and Polytetrafluoroethylene). The electrostatic charge profiles of pMDI formulations containing beclomethasone dipropionate (BDP) as model drug, in HFA-134a propellant, with different concentrations of ethanol were studied with different actuator designs. Electrostatic measurements were taken using a modified electrical low-pressure impactor (ELPI) and the deposited drug mass was assayed chemically using HPLC.

Results: The charge profiles of HFA 134a propellant alone have shown strong electronegativity with all actuator materials and nozzle designs, at an average of –1531.34 pC ± 377.34. The presence of co-solvent ethanol significantly reduced the negative charge magnitude of HFA 134a, with 15% ethanol producing a net charge close to neutral for all actuator designs. BDP reduces the suppressing effect of ethanol on the negative charging property of the propellant. For all tested formulations, the flat nozzle design shown no significant differences between different actuator materials, where for the cone designs the net charge profile ranking follows the triboelectric series.  

Conclusion: The electrostatic charging profiles arising from a solution pMDI formulation containing BDP and ethanol as co-solvent can be significantly influenced by the actuator material, nozzle design and formulation components. Ethanol concentration appears to have the most significant impact. Furthermore, it has been shown that BDP interactions with ethanol and HFA could have an influence on the electrostatic charge of the aerosol. By choosing a different combination of actuator materials and orifice design, the fine particle fractions of the formulation can be altered.

Objectives: The formulation of a clarithromycin (CLA) pressurised metered dose inhalers (pMDIs) solution formulation opens up exciting therapeutic opportunities for the treatment of inflammation in chronic obstructive lung diseases. In this study we have formulated and tested a low dose macrolide formulation of CLA for treatment of inflammation and studied its physico-chemical and aerosol properties.

Methods: The system was characterised for in vitro aerosol performance using an Anderson cascade impactor. Short-term chemical and physical stability was assessed by dose content uniformity over a range of temperatures. Standard physico-chemical characteristics were also investigated using scanning electron microscopy, thermo analysis and laser diffraction techniques. 

Results and discussion: The formulation had a relatively high fine particle fraction (47%) and produced a particle size distribution suitable for inhalation drug delivery. Particles had an irregular morphology and were predominately amorphous. Furthermore, the short-term stability showed the formulation to be stable from 4-37°C.

Conclusions: This study demonstrated the feasibility of formulating a solution-based pMDI containing of CLA for the treatment of lung inflammatory diseases.

Purpose: The potential for rifapentine-containing oral therapeutic regimens to significantly shorten the current six-month anti-tubercular treatment regimen is confounded by high plasma protein binding of rifapentine. Inhaled aerosol delivery of rifapentine, a more potent anti-tubercular antibiotic drug, in combination with other first- line antibiotics may overcome this limitation to deliver a high drug dose at the pulmonary site of infection. Method: A formulation consisting of rifapentine, moxifloxican and pyrazinamide with and without leucine was prepared by spray-drying. This formulation was assessed for its physico-chemical properties, and in vitro aerosol performance and antimicrobial activity. Results: The antibiotic powders, with and without leucine, had similar median aerodynamic diameters of 2.58 ± 0.08 μm and 2.51 ± 0.06 μm, with a relatively high fine particle fraction of 55.5 ± 1.9% and 63.6 ± 2.0%, respectively. Although the powders were mostly amorphous, some crystalline peaks associated with the δ polymorph for the spray-dried crystalline pyrazinamide were identified. Conclusions: Stabilisation of the powder with 10% w/w leucine and protection from moisture ingress was found to be necessary to prevent the crystallisation of pyrazinamide after long-term storage. In vitro biological assays indicated antimicrobial activity was retained after spray-drying. Murine pharmacokinetic studies are currently underway.

A critical problem associated with poor water-soluble drugs is their low and variable bioavailability, which is derived from the slow dissolution and erratic absorption. Nano-formulation has been identified as one approach to enhance the rate and extent of drug absorption for compounds that demonstrate limited water solubility. This study aimed to investigate the physico-chemical variables that affect the manufacture, dissolution and consequent bioavailability of wet-milled clarithromycin (CLA) nanoparticles, a macrolide antibiotic. CLA nanoparticles were prepared using wet milling method followed by freeze-drying. Different stabilizer systems, consisting of surfactants and polymers alone or their combinations were studied to determine the optimum conditions for producing nano-sized CLA particles. In vitro characterizations of the CLA nanoparticles were performed using photon correlation spectroscopy, X-ray powder diffraction, differential scanning calorimetry and dissolution efficiency test. Results showed that in general the wet milling process did not modify the crystallinty of the CLA nanoparticles. The poloxamers and poly vinyl alcohol (PVA) stabilizers resulted in nanoparticles with the smallest particle size and best dissolution rates. Furthermore, poloxamers F68 and F127, and PVA stabilizers demonstrated the best performance in increasing dissolution efficacy.

The aim of the present study was to develop controlled release inhalable lipid microparticles (LMs) loaded with the antioxidant flavonoid, quercetin and to investigate the interaction of these microparticles with A549 pulmonary alveolar epithelial cells. The LMs were produced using different lipidic materials and surfactants, by melt emulsification followed by a sonication step. The most efficient modulation of the in vitro release of quercetin was achieved when LMs were prepared with tristearin and hydrogenated phosphatidylcholine; which were used for subsequent studies.

These LMs exhibited a quercetin loading of 11.8±0.3%, and a volume median diameter, determined by laser diffraction, of 4.1±0.2 μm.  Moreover, their mass median aerodynamic diameter (4.82 ±0.15 μm) and fine particle fraction (27.2±3.9%), as measured by multi-stage liquid impinger, were suitable for pulmonary delivery. Quercetin was found to be highly unstable (complete decomposition within 6-h incubation) in Ham’s F-12 medium used for A549 cell culture. Degradation was markedly reduced (16.4% of the initial quercetin content still present after 24-h incubation) after encapsulation in the lipid system. 

Viability studies performed by lactate dehydrogenase assay, demonstrated that quercetin LMs showed no significant cytotoxicity on the A549 cells, over the concentration 0.1-5 μM. The uptake of quercetin by the A549 lung alveolar cells was also investigated.  After 4-h incubation, the accumulation of quercetin in the A549 cells was significantly higher (2.3-fold increase) for the microparticle entrapped flavonoid when compare to non-encapsulated quercetin. The enhanced intracellular delivery of quercetin achieved by the LMs is likely due to the flavonoid stabilization after encapsulation. 

Purpose: A new approach to delivering high doses of dry powder medicaments to the lung is presented. The Orbital dry powder device (DPI) is designed to deliver high-doses of drugs to the respiratory tract in a single dosing unit, via multiple inhalation manoeuvrers, overcoming the need to prime or insert multiple capsules.

Methods: The Orbital was tested in its prototype configuration and compared to a conventional RS01 capsule device. Three formulations were evaluated: 200 mg spray-dried ciprofloxacin formulation for respiratory infection, 200 mg spray-dried mannitol formulation for mucus clearance, and 100, 200 and 400 mg co-spray dried 1:8 formulations containing ciprofloxacin and mannitol as combination therapy. The systems were evaluated in terms of physico-chemical properties and tested using a multistage liquid impinger at 60 L/min. Emptying rates were evaluated and the aerosolisation performance compared to 10 capsules used sequentially in the RS01. 

Results and Discussion: The systems were different in terms of morphology, thermal response, moisture sorption and stability; however, they had similar sizes when measured by laser diffraction making them suitable for comparison in the Orbital and RS01 devices. The aerosolisation performance from the Orbital and RS01 was dependent upon the formulation type; however, the fine particle fraction (FPF) produced by the Orbital device was higher than the RS01.  The FPF for ciprofloxacin, mannitol and co-spray dried formulation were 67.1±1.8, 47.1 ±2.2 and 42.0 ±1.8, respectively. For the Orbital, 90% of the loaded dose was delivered within 10 inhalation maneuvers, with the profile being dependent upon the formulation type. 

Conclusion: The Orbital provides a means of delivering high doses of medicine to the respiratory tract through multiple breath maneuvers after a single actuation. This approach will allow the delivery of a wide range of high-pay load formulations (>100 mg) for the treatment of a variety of lung disorders. To date no such passive device exists that meet these crucial criteria.

Inhalation of antibiotics and mucolytics are the most important combination of inhaled drugs for chronic obstructive lung diseases and have become a standard part of treatment. However, it is yet to be determined whether the administration of a mucolytic has an effect on the transport rate of antibiotics across the airway epithelial cells. Consequently, the aim of this study was to investigate the effects of inhalation dry powder, specifically mannitol, on ciprofloxacin transport using Calu-3 air interface cell model. Transport studies of ciprofloxacin HCl were performed using different configurations including single spray-dried ciprofloxacin alone, co-spray dried ciprofloxacin with mannitol and deposition of mannitol prior to ciprofloxacin deposition. To understand the mechanism of transport and interactions between the drugs, pH measurements of apical surface liquid and further transport studies were performed with ciprofloxacin base, with and without the presence of ion channel/transport inhibitors such as disodium cromoglycate and furosemide. Mannitol was found to delay absorption of ciprofloxacin HCl through the increase in ASL volume and subsequent reduction in pH. Conversely, ciprofloxacin base had a higher transport rate after mannitol deposition. This study clearly demonstrates that the deposition of mannitol prior to ciprofloxacin on the air-interface Calu-3 cell model has an effect on its transport rate. This was also dependent on the salt form of the drug and the timing and sequence of formulations administered.