Cascade Impactor Performance of Commercial pMDI Formulations Using Modified Induction Ports.

The induction port (IP) for aerosol analysis with the Next Generation Pharmaceutical Impactor as monographed in the United States and European pharmacopoeia (USPIP) lacks physiological relevance, which, amongst other reasons, has been identified as critical for the predictability of in vitro aerosol data to lung deposition observed in vivo. In this publication, we report the impact of replacing the USPIP with two modified induction ports, which were designed based around geometries derived from a computer tomographic scan of a human trachea and the distal section of the USPIP. Test formulations were selected on the basis of availability of in vivo lung deposition data so that results obtained in vitro could be evaluated for their predictability. All formulations assessed showed increased deposition in the modified induction ports, and different mechanisms of particle deposition have been identified. In vitro predictions of the lung deposition were found to correlate well with the in vivo observations reported using the modified induction ports. Furthermore, the quality of the correlation was found superior to the one achieved with the USPIP with an average deviation of the predicted from observed values (n = 10) of 6 ± 4, 12 ± 6, and 16 ± 6% for the modified induction ports (mIP and mIPext) and the USPIP, respectively, when using a fine particle fraction (FPF) cutoff value of 5 µm. Using a FPF cutoff value of 3 µm yielded a more accurate in vitro-in vivo correlation with an average deviation of the predicted from observed values of 5 ± 4, 7 ± 5, and 8 ± 4% for the mIP, mIPext, and USPIP, respectively. For both FPF size cutoff values, the mIP yielded the most accurate in vitro-in vivo correlation.

Devices for dry powder drug delivery to the lung.

Dry powder inhalers (DPIs) are an important and increasingly investigated method of modern therapy for a growing number of respiratory diseases. DPIs are a promising option for certain patient populations, and may help to overcome several limitations that are associated with other types of inhalation delivery systems (e.g., accuracy and reproducibility of the dose delivered, compliance and adherence issues, or environmental aspects). Today, more than 20 different dry powder inhalers are on the market to deliver active pharmaceutical ingredients (APIs) for local and/or systemic therapy. Depending on the mechanism of deagglomeration, aerosolization, dose metering accuracy, and the interpatient variability, dry powder inhalers demonstrate varying performance levels. During development, manufacturers focus on improving aspects characteristic of their specific DPI devices, depending on the intended type of application and any particular requirements associated with it. With the wide variety of applications related to specific APIs, there exists a range of different devices with distinct features. In addition to the routinely used multi-use DPIs, several single-use disposable devices are under development or already approved. The recent introduction of disposable devices will expand the range of possible applications for use by including agents such as vaccines, analgesics, or even rescue medications. This review article discusses the performance and advantages of recently approved dry powder inhalers as well as disposable single-use inhalers that are currently under development.

Novel strategies for the buccal delivery of macromolecules.

For years now, the delivery of small molecules through the buccal mucosal route has been described in the literature, but it has only been over the past decade that investigations into macromolecule delivery via the buccal route have sharply increased. The administration of macromolecules such as proteins and peptides, antibodies, or nucleic acids by buccal administration would be greatly enhanced due to the avoidance of the gastrointestinal conditions, rapid uptake into systemic circulation, as well as the potential for controlled drug delivery. Since macromolecules are faced with a number of specific challenges related to permeation through the epithelium, several strategies have been employed historically to improve their buccal absorption and subsequent bioavailability. Several conventional strategies to improve macromolecule penetration include the use of chemical permeation enhancers, enzyme inhibitors and the use of mucoadhesive materials acting as carriers. More recent approaches include the incorporation of the macromolecule as part of nanostructured delivery systems to further enhance targeting and delivery. This review focuses on the different permeation enhancing strategies as well as formulation design that are tailored to meet the challenges of active macromolecule delivery using the buccal mucosal route of administration.

Focused ion beam-scanning electron microscopy provides novel insights of drug delivery phenomena.

Scanning electron microscopy (SEM) has long been a standard tool for morphological analyses, providing sub micrometer resolution of pharmaceutical formulations. However, analysis of internal morphologies of such formulations can often be biased due to the introduction of artifacts that originate from sample preparation. A recent advancement in SEM, is the focused ion beam scanning electron microscopy (FIB-SEM). This technique uses a focused ion beam (FIB) to remove material with nanometer precision, to provide virtually sample-independent access to sub-surface structures. The FIB can be combined with SEM imaging capabilities within the same instrumentation. As a powerful analytical tool, electron microscopy and FIB-milling are performed sequentially to produce high-resolution 3D models of structural peculiarities of diverse drug delivery systems or their behavior in a biological environment, i.e. intracellular or -tissue distribution. This review paper briefly describes the technical background of the method, outlines a wide array of potential uses within the drug delivery field, and focuses on intracellular transport where high-resolution images are an essential tool for mechanistical insights.

Size discrimination in rat and mouse gastric emptying.

OBJECTIVES: To investigate the relationship between particle size and gastric emptying in rodents using radiolabeled insoluble polymethyl methacrylate (PMMA) microcapsules/beads. METHODS: PMMA microcapsules (50-500 µm) and beads (0.5-3 mm) loaded with technetium-99 m diethylenetriamine pentaacetic acid ((99m) Tc-DTPA) were administered to ICR mice or Sprague Dawley (SD) rats by oral gavage. Gamma scintiscans were acquired initially following administration and then at hourly intervals to 4 hours. RESULTS: Scintiscans revealed that the smallest PMMA microcapsules (50-100 µm) or beads (0.5-1 mm) were impeded in the stomach and emptied slower than large particles in both rodent species. In mice, no significant difference in gastric emptying was found with microcapsules between 100 and 300 µm in diameter (p = 0.25) and particles more than 300 µm could not be administered. In rats, capsules containing 0.5-3 mm beads were stuck to the esophagus (up to 1 hour), this was a limitation of dosing beads of this size because they cannot be suspended in a liquid media for oral gavage purposes. Beads with diameters of 2-3 mm stayed in the stomach for up to 4 hours. CONCLUSIONS: The cut-off emptying size in ICR mice could not be determined, due to the limitation of current available dosing methods. The cut-off emptying size in SD rats was between 1.5 and 2 mm. Therefore, particles with a diameter greater than 2 mm should not be used for gastric emptying studies of intact particles in SD rats, as their emptying is retarded in the stomach.

Development and characterization of phospholipid-stabilized submicron aqueous dispersions of coenzyme Q10 presenting continuous vibrating-mesh nebulization performance.

Coenzyme Q10 (CoQ10) is a poorly-water soluble compound that is being investigated for the treatment of carcinomas. The aim of this research was to develop a suitable formulation for pulmonary delivery of this anticancer agent. An appropriate selection of excipients (phospholipids) and a suitable device (Aeroneb Pro® vibrating-mesh nebulizer) were selected initially after reviewing the literature. After characterization of the bulk drug, a feasible manufacturing process was selected to obtain small particle size dispersions of CoQ10. Following selection of an appropriate process, the parameters affecting drug particle size were studied. Using LD and gravimetrical analysis, nebulization was evaluated to assess the performance of the inhalation system triad: drug-excipients-device. CoQ10 powder studied was crystalline with a melting point approximately at 51 °C and with a particle size of 30 µm. Microfluidization was found to be a suitable method to prepare submicron drug particles in aqueous dispersions. Increasing microfluidization processing to more than 50 passes did not provide further particle downsizing for both soya phosphatidylcholine (lecithin) and dipalmitoyl phosphatidylcholine (DPPC) dispersions of CoQ10, presenting Z-average values of approximately 130 and 70 nm, respectively. Nebulization performance of lecithin-stabilized CoQ10 dispersions varied according to number of passes in the microfluidizer. Formulations processed with 10 passes presented steadier nebulization over time and different rheological behavior compared to those processed with 30 or 50 passes. In conclusion, aqueous dispersions of CoQ10 were adequately produced using a microfluidizer with characteristics that were suitable for pulmonary delivery with an Aeroneb Pro® nebulizer. Furthermore, the rheology of these dispersions appeared to play a significant role in the aerosol generation from the active vibrating-mesh nebulizer used.

A design of experiments to optimize a new manufacturing process for high activity protein-containing submicron particles.

A novel method for the manufacture of protein/peptide-containing submicron particles was developed in an attempt to provide particles with increased activity while using high energy input technologies. The method consists of antisolvent co-precipitation from an aqueous solution containing both an amino acid core material (e.g. D,L-valine), and either bovine serum albumin (BSA) or lysozyme (Lys) as model proteins. The aqueous solution was added to the organic phase by means of a nebulizer to increase the total surface area of interaction for the precipitation process. Sonication proved to be an effective method to produce small particle sizes while maintaining high activity of Lys. The use of a polysorbate or sorbitan ester derivatives as stabilizers proved to be necessary to yield submicron particles. Particles with very high yields (approximately 100%) and very high activity after manufacture (approximately 100%) could be obtained. A particle size of 439.0 nm, with a yield of 48.8% and with final remaining activity of 98.7% was obtained. By studying various factors using a design of experiments strategy (DoE) we were able to establish the critical controlling factors for this new method of manufacture.

The influence of recrystallized caffeine on water-swellable polymethacrylate mucoadhesive buccal films.

The aim of this work was to investigate the influence of particles on the properties of polymethacrylate films intended for buccal delivery. A solvent casting method was used with Eudragit RS and RL (ERS and ERL, respectively) as film-forming rate-controlling polymers, with caffeine as a water-soluble model drug. The physicochemical properties of the model films for a series of formulations with increasing concentrations of caffeine were determined in terms of morphology, mechanical and mucoadhesive properties, drug content uniformity, and drug release and associated kinetics. Typically regarded as non-mucoadhesive polymers, ERS and mainly ERL, were found to be good mucoadhesives, with ERL01 exhibiting a work of mucoadhesion (WoA) of 118.9 µJ, which was about five to six times higher than that observed for commonly used mucoadhesives such as Carbopol(®) 974P (C974P, 23.9 µJ) and polycarbophil (PCP, 17.4 µJ). The mucoadhesive force for ERL01 was found to be significantly lower yet comparable to C974P and PCP films (211.1 vs. 329.7 and 301.1 mN, respectively). Inspection of cross-sections of the films indicated that increasing the concentration of caffeine was correlated with the appearance of recrystallized agglomerates. In conclusion, caffeine agglomerates had detrimental effects in terms of mucoadhesion, mechanical properties, uniformity, and drug release at large particle sizes. ERL series of films exhibited very rapid release of caffeine while ERS series showed controlled release. Analysis of release profiles revealed that kinetics changed from a diffusion controlled to a first-order release mechanism.

Application of a pull on a disk method to measure surface tension of liquids.

The intrinsic property of liquids is a vital indicator of formulation performance and stability. Therefore, investigation of the interfacial phenomenon of surface tension is a routine procedure in the development of products in a wide variety of areas including foods, pharmaceuticals, cosmetics, and painting technologies. We hypothesize that studies related to the maximum pull on a rod can be extrapolated to disk geometry and applied to measure surface tension using a texture analyzer. A glass disk probe was attached to the arm of a texture analyzer and pulled from the liquid surface. The maximum force of detachment was used to calculate surface tension extrapolating from the theory of maximum pull on a rod. The surface tension of water, ethanol, and a hydroalcoholic solution was measured and compared with literature values to validate this hypothesis. The calculated values of surface tension for the liquids studied were within 5% of the reported values. Probe diameter appears to have an important role on surface tension accuracy compared with literature values. Slight discrepancies can be attributed to temperature control and leveling of liquid surface, although still in accordance with the reported values of surface tension measured using different methods. This study presents a simple, precise, and quick method to determine the surface tension of liquids from the maximum pull on a disk. Further studies are warranted to determine the optimum glass disk probe diameter for better accuracy.

Inhalable formulations of rifampicin by spray drying of supersaturated aqueous solutions.

Tuberculosis is still one of the leading causes of death from a single infectious agent (i.e. Mycobacterium tuberculosis). First line therapy includes per oral administration of high doses of rifampicin over several months and is often times accompanied by the occurrence of unwanted side effects that might limit the patient's adherence to the therapy. Thus, local antibiotic treatment at the site of infection i.e. the lungs is desirable. Amongst other approaches, spray drying of solutions of rifampicin has been shown as suitable method to produce respirable dry powders. In this work, we present inhalable formulations manufactured via spray drying of aqueous solutions of rifampicin. Powders manufactured were characterized for their aerodynamic and solid state properties, as well as their physical and chemical stability. The main focus of this study was to investigate the mechanism of particle formation using an acoustic levitator. Fine particle fractions of the test formulations ranged from 80 to 89% whereas a reference formulation (a spray dried isopropyl alcoholic solution of rifampicin) showed a lower fine particle fraction of 37%. Acoustic levitator and surface tension experiments showed that interfacial properties of rifampicin lead to early crust formation upon drying of the droplets, which eventually decoupled from the liquid core and formed highly collapsed, low apparent density powders with excellent aerosol properties.

(Solvato-) polymorphism of formulations of rifampicin for pulmonary drug delivery prepared using a crystallization/spray drying process.

Rifampicin is an antibiotic used in tuberculosis therapy showing extensive (solvato-) polymorphism. Per oral administration of high doses is recommended, but application as dry powder for inhalation at the site of infection being the lungs, is desirable. Recrystallization from ethanol and consecutive spray drying is reported to yield a rifampicin dihydrate with suitable aerosol performance and stability. Nevertheless, the origin of water in the crystal remained unclear and demanded further investigation so to clarify its solid state throughout manufacture and storage. The present study reports the relationship of (solvato-) polymorphs occurring during manufacture and storage of samples recrystallized and spray dried from ethanol, methanol and water and it was concluded that processes involving a recrystallization from EtOH and MeOH produce particles of a common isostructural group of channel solvates. Samples recrystallized and spray dried from water were identified as members of another isostructural group, which was already characterized in literature. As a second aim, aerosol performance and storage stability of the formulations were investigated and all samples showed stable aerosol performance. Chemical stability of samples spray dried from ethanol was found suitable over a period of six months, whereas samples spray dried from methanol or water showed significant degradation.

Inhalable dry powders of rifampicin highlighting potential and drawbacks in formulation development for experimental tuberculosis aerosol therapy.

Introduction: Recently, tuberculosis was reported as the leading cause of death from a single infectious agent. Standard therapy includes administration of four first-line antibiotics, i.e. rifampicin, isoniazid, ethambutol, and pyrazinamide over a period of at least 26 weeks, which in case of rifampicin oftentimes is accompanied by unwanted side effects and variable bioavailability that compromise a positive therapeutic outcome. As the main site of infection is the lungs, it is desirable to develop a therapeutic formulation to be administered via the pulmonary route.Areas covered: This work presents a literature review on studies investigating inhalable dry powder formulations including rifampicin in the context of an experimental tuberculosis therapy, with a special focus on aerosol performance.Expert opinion: It was found that formulation approaches involving different strategies and functional excipients are under investigation but as of now, no formulation has managed to leap into commercial clinical testing. Reasons for this might not primarily be associated with a lack of suitable candidates, but amongst others a lack of suitable in vitro models to assess the efficacy, therapeutic benefit, and cost-effectiveness of the candidate formulations.

Inhaled voriconazole for prevention of invasive pulmonary aspergillosis.

Targeted airway delivery of antifungals as prophylaxis against invasive aspergillosis may lead to high lung drug concentrations while avoiding toxicities associated with systemically administered agents. We evaluated the effectiveness of aerosolizing the intravenous formulation of voriconazole as prophylaxis against invasive pulmonary aspergillosis caused by Aspergillus fumigatus in an established murine model. Inhaled voriconazole significantly improved survival and limited the extent of invasive disease, as assessed by histopathology, compared to control and amphotericin B treatments.

Nebulization of nanoparticulate amorphous or crystalline tacrolimus--single-dose pharmacokinetics study in mice.

Developing a pulmonary composition of tacrolimus (TAC) provides direct access to the graft in lung transplant offering the possibility of high drug levels. The objective of this study was to investigate the physicochemical and pharmacokinetic characteristics of the nanostructured aggregates containing amorphous or crystalline nanoparticles of TAC produced by ultra-rapid freezing (URF). TAC and lactose (1:1 ratio; URF-TAC:LAC) and TAC alone (URF-TAC) were investigated for pulmonary delivery and compared to unprocessed TAC. X-ray diffraction (XRD) results indicated that URF-TAC was crystalline, whereas URF-TAC:LAC was amorphous. In vitro results revealed the superior physiochemical characteristics of both URF formulations compared to unprocessed TAC. The surface area of URF processed TAC was higher (25-29 m2/g) than that of the unprocessed TAC (0.53 m2/g) and subsequently enhanced dissolution rates. In addition, URF-TAC:LAC displayed the ability to supersaturate in the dissolution media to about 11 times the crystalline equilibrium solubility. Similar aerodynamic particle sizes of 2-3 microm, and fine particle fraction between 70% and 75% were found in both formulations. The local and systemic pharmacokinetic studies in mice showed similar AUC(0-24), higher Cmax, and lower Tmax for the URF-TAC:LAC compared to the URF-TAC. Nanostructured aggregates containing amorphous or crystalline nanoparticles of TAC were demonstrated to be effectively delivered via nebulization, with similar in vitro and in vivo performances.

High bioavailability from nebulized itraconazole nanoparticle dispersions with biocompatible stabilizers.

A nebulized dispersion of amorphous, high surface area, nanostructured aggregates of itraconazole (ITZ):mannitol:lecithin (1:0.5:0.2, w/w) yielded improved bioavailability in mice. The ultra-rapid freezing (URF) technique used to produce the nanoparticles was found to molecularly disperse the ITZ with the excipients as a solid solution. Upon addition to water, ITZ formed a colloidal dispersion suitable for nebulization, which demonstrated optimal aerodynamic properties for deep lung delivery and high lung and systemic levels when dosed to mice. The ITZ nanoparticles produced supersaturation levels 27 times the crystalline solubility upon dissolution in simulated lung fluid. A dissolution/permeation model indicated that the absorption of 3 microm ITZ particles is limited by the dissolution rate (BCS Class II behavior), while absorption is permeation-limited for more rapidly dissolving 230 nm particles. The predicted absorption half-life for 230 nm amorphous ITZ particles was only 15 min, as a result of the small particle size and high supersaturation, in general agreement with the in vivo results. Thus, bioavailability may be enhanced, by decreasing the particle size to accelerate dissolution and increasing permeation with (1) an amorphous morphology to raise the drug solubility, and (2) permeability enhancers.

Advancements in dry powder delivery to the lung.

The dry powder inhaler (DPI) has become widely known as a very attractive platform for drug delivery. Many patients have traditionally used DPIs to treat asthma and chronic obstructive pulmonary disease. Recently, the development of new DPIs for delivering therapeutic proteins such as insulin has been accelerated by patient demands, and innovative research. The current market for DPIs has over 20 devices presently in use, and many devices under development for delivering a variety of therapeutic agents. DPIs are recognized as suitable alternatives to pressurized metered dose inhalers for some patients, but the performance of DPI devices may vary according to a given patient's physiological condition. This variation can be associated with the necessary powder dispersion mechanism of each device. As such, much interest has focused on the development of efficient powder dispersion mechanisms, as this effectively minimizes the influence of interpatient variability. This article reviews DPI devices currently available, advantages of newly developed devices, outlines some requirements for future device design.

Current therapies and technological advances in aqueous aerosol drug delivery.

Recent advances in aerosolization technology have led to renewed interest in pulmonary delivery of a variety of drugs. Pressurized metered dose inhalers (pMDIs) and dry powder inhalers (DPIs) have experienced success in recent years; however, many limitations are presented by formulation difficulties, inefficient delivery, and complex device designs. Simplification of the formulation process as well as adaptability of new devices has led many in the pharmaceutical industry to reconsider aerosolization in an aqueous carrier. In the acute care setting, breath-enhanced air-jet nebulizers are controlling and minimizing the amount of wasted medication, while producing a high percentage of respirable droplets. Vibrating mesh nebulizers offer advantages in higher respirable fractions (RFs) and slower velocity aerosols when compared with air-jet nebulizers. Vibrating mesh nebulizers incorporating formulation and patient adaptive components provide improvements to continuous nebulization technology by generating aerosol only when it is most likely to reach the deep lung. Novel innovations in generation of liquid aerosols are now being adapted for propellant-free pulmonary drug delivery to achieve unprecedented control over dose delivered and are leading the way for the adaptation of systemic drugs for delivery via the pulmonary route. Devices designed for the metered dose delivery of insulin, morphine, sildenafil, triptans, and various peptides are all currently under investigation for pulmonary delivery to treat nonrespiratory diseases. Although these devices are currently still in clinical testing (with the exception of the Respimat), metered dose liquid inhalers (MDLIs) have already shown superior outcomes to current pulmonary and systemic delivery methods.

Investigating cascade impactor performance using a modified 3D printed induction port.

Based on a computer tomographic scan of a human trachea, a modified induction port (mIP), for use with the Next Generation Cascade Impactor, was manufactured using 3D printing technology. Standard United States Pharmacopoeia IP (USPIP) was compared to the mIP and a 3D printed version of the USPIP (USP3DIP) by analyzing different types of commercial salbutamol formulations for inhalation. Increased retention of particles in the mIP was found analyzing a pMDI formulation, leading to a decrease in the FPF from 28.8±2.0% to 14.2±1.2%, which correlates better to in vivo deposition data from literature. Increased deposition was found to be based on geometrical factors only. The impact of surface related effects was investigated by (a) comparing results obtained with the USPIP and USP3DIP (all formulations) and (b) generating another model IP (USP3DSEIP) with a surface area equivalent to the mIP but maintaining the geometry of the USPIP (pMDI only). USPIP, USP3DIP, and USP3DSEIP were found to perform equivalently. The impact of different geometries on airflow velocities in the USPIP and mIP was assessed using a computational fluid dynamics (CFD) model. Conclusively, this study shows that replacing the USP IP by the mIP can provide additional information in formulation assessment and in in vitro/in vivo correlation, when applied on pMDI formulations.

Nebulized coenzyme Q10 nanosuspensions: A versatile approach for pulmonary antioxidant therapy.

Coenzyme Q10 (CoQ10) is an antioxidant substance indicated as a dietary supplement which has been proposed as adjuvant in the treatment of cardiovascular disorders and cancer for its protective and immunostimulating activities. The aim of this work was the production by high-pressure homogenization, characterization and stability investigation of three different CoQ10 nanosuspensions designed to be administered to the lungs by nebulization. Three surfactants, i.e. lecithin, PEG32 stearate and vitamin-E TPGS, were selected to stabilize CoQ10 formulations. Preparations were identified as nanosuspensions (particle size in the range 35-60nm): the smallest particles were obtained with vitamin-E TPGS and denoted a core-shell structure. The CoQ10 delivered from a commercial air-jet nebulizer was in all the cases around 30% of the loaded dose. The nanosuspension containing PEG32 stearate presented the highest respirable fraction (70.6%) and smallest MMAD (3.02µm). Stability tests showed that the most stable formulation, after 90days, was the one containing vitamin-E TPGS, followed by the CoQ10-lecithin formulation. Interestingly, those formulations were demonstrated to be suitable also for nebulizers using other mechanisms of aerosol production such as ultrasound and vibrating mesh nebulizers. Studies focused on in vitro cellular toxicity of the formulations and their single components using A549 human lung cells showed no obvious cytotoxicity for the formulations containing lecithin and PEG 32 stearate. Vitamin-E TPGS alone was shown to be able to damage the plasma membrane, nevertheless, cell damage was decreased when vitamin-E TPGS was present in the formulation with CoQ10.