The Influence of Mechanical Processing of Dry Powder Inhaler Carriers on Drug Aerosolization Performance

Development of favipiravir dry powders for intranasal delivery: An integrated cocrystal and particle engineering approach via spray freeze drying

The therapeutic potential of pharmaceutical cocrystals in intranasal applications remains largely unexplored despite progressive advancements in cocrystal research. We present the application of spray freeze drying (SFD) in successful fabrication of a favipiravir-pyridinecarboxamide cocrystal nasal powder formulation for potential treatment of broad-spectrum antiviral infections. Preliminary screening via mechanochemistry revealed that favipiravir (FAV) can cocrystallize with isonicotinamide (INA), but not nicotinamide (NCT) and picolinamide (PIC) notwithstanding their structural similarity. The cocrystal formation was characterized by differential scanning calorimetry, Fourier-transform infrared spectroscopy, and unit cell determination through Rietveld refinement of powder X-ray analysis. FAV-INA crystalized in a monoclinic space group P21/c with a unit cell volume of 1223.54(3) Å3, accommodating one FAV molecule and one INA molecule in the asymmetric unit. The cocrystal was further reproduced as intranasal dry powders by SFD, of which the morphology, particle size, in vitro drug release, and nasal deposition were assessed. The non-porous flake shaped FAV-INA powders exhibited a mean particle size of 19.79 ± 2.61 μm, rendering its suitability for intranasal delivery. Compared with raw FAV, FAV-INA displayed a 3-fold higher cumulative fraction of drug permeated in Franz diffusion cells at 45 min (p = 0.001). Dose fraction of FAV-INA deposited in the nasal fraction of a customized 3D-printed nasal cast reached over 80 %, whereas the fine particle fraction remained below 6 % at a flow rate of 15 L/min, suggesting high nasal deposition whilst minimal lung deposition. FAV-INA was safe in RPMI 2650 nasal and SH-SY5Y neuroblastoma cells without any in vitro cytotoxicity observed. This study demonstrated that combining the merits of cocrystallization and particle engineering via SFD can propel the development of advanced dry powder formulations for intranasal drug delivery.

Dry Powder Inhalers: An Overview

Dry powder inhaler products have played an important role in the treatment and prevention of asthma and more recently chronic obstructive pulmonary disease. The considerations that go into formulation development to support these products cover a unique range of disciplines including analytical and physical chemistry, aerosol physics, device technology, process engineering and industrial design. An enormous research effort has been expended in the last half century to provide understanding of this complex dosage form. The guiding principles in considering the development of dry powder inhaler products encompass requirements for disease therapy, advantages and limitations of adopting certain technological approaches, and desirable features to facilitate patient use, which are all embodied in the target product profile.

Preparation and Evaluation of Inhalable Amifostine Microparticles Using Wet Ball Milling

The conventional dosage form of Ethyol^® (amifostine), a sterile lyophilized powder, involves reconstituting it with 9.7 mL of sterile 0.9% sodium chloride in accordance with the United States Pharmacopeia specifications for intravenous infusion. The purpose of this study was to develop inhalable microparticles of amifostine (AMF) and compare the physicochemical properties and inhalation efficiency of AMF microparticles prepared by different methods (jet milling and wet ball milling) and different solvents (methanol, ethanol, chloroform, and toluene). Inhalable microparticles of AMF dry powder were prepared using a wet ball-milling process with polar and non-polar solvents to improve their efficacy when delivered through the pulmonary route. The wet ball-milling process was performed as follows: AMF (10 g), zirconia balls (50 g), and solvent (20 mL) were mixed and placed in a cylindrical stainless-steel jar. Wet ball milling was performed at 400 rpm for 15 min. The physicochemical properties and aerodynamic characteristics of the prepared samples were evaluated. The physicochemical properties of wet-ball-milled microparticles (WBM-M and WBM-E) using polar solvents were confirmed. Aerodynamic characterization was not used to measure the % fine particle fraction (% FPF) value in the raw AMF. The % FPF value of JM was 26.9 ± 5.8%. The % FPF values of the wet-ball-milled microparticles WBM-M and WBM-E prepared using polar solvents were 34.5 ± 0.2% and 27.9 ± 0.7%, respectively; while the % FPF values of the wet-ball-milled microparticles WBM-C and WBM-T prepared using non-polar solvents were 45.5 ± 0.6% and 44.7 ± 0.3%, respectively. Using a non-polar solvent in the wet ball-milling process resulted in a more homogeneous and stable crystal form of the fine AMF powder than using a polar solvent.

Focusing on powder processing in dry powder inhalation product development, manufacturing and performance

Dry powder inhalers (DPI) are well established products for the delivery of actives via the pulmonary route. Various DPI products are marketed or developed for the treatment of local lung diseases such as chronic obstructive pulmonary disease (COPD), asthma or cystic fibrosis as well as systemic diseases targeted through inhaled delivery (i.e. Diabetes Mellitus). One of the key prerequisites of DPI formulations is that the aerodynamic size of the drug particles needs to be below 5 µm to enter deeply into the respiratory tract. These inherently cohesive inhalable size particles are either formulated as adhesive mixture with coarse carrier particles like lactose called carrier-based DPI or are formulated as free-flowing carrier-free particles (e.g. soft agglomerates, large hollow particles). In either case, it is common practice that drug and/or excipient particles of DPI formulations are obtained by processing API and API/excipients. The DPI manufacturing process heavily involves several particle and powder technologies such as micronization of the API, dry blending, powder filling and other particle engineering processes such as spray drying, crystallization etc. In this context, it is essential to thoroughly understand the impact of powder/particle properties and processing on the quality and performance of the DPI formulations. This will enable prediction of the processability of the DPI formulations and controlling the manufacturing process so that meticulously designed formulations are able to be finally developed as the finished DPI dosage form. This article is intended to provide a concise account of various aspects of DPI powder processing, including the process understanding and material properties that are important to achieve the desired DPI product quality. Various endeavors of model informed formulation/process design and development for DPI powder and PAT enabled process monitoring and control are also discussed.

A quantitative approach to predicting lung deposition profiles of pharmaceutical powder aerosols

Dry powder inhalers (DPI) are widely used systems for pulmonary delivery of therapeutics. The inhalation performance of DPIs is influenced by formulation features, inhaler device and inhalation pattern. The current review presents the affecting factors with great focus on powder characteristics which include particle size, shape, surface, density, hygroscopicity and crystallinity. The properties of a formulation are greatly influenced by a number of physicochemical factors of drug and added excipients. Since available particle engineering techniques result in particles with a set of modifications, it is difficult to distinguish the effect of an individual feature on powder deposition behavior. This necessitates developing a predictive model capable of describing all influential factors on dry powder inhaler delivery. Therefore, in the current study, a model was constructed to correlate the inhaler device properties, inhalation flow rate, particle characteristics and drug/excipient physicochemical properties with the resultant fine particle fraction. The r² value of established correlation was 0.74 indicating 86% variability in FPF values is explained by the model with the mean absolute errors of 0.22 for the predicted values. The authors believe that this model is capable of predicting the lung deposition pattern of a formulation with an acceptable precision when the type of inhaler device, inhalation flow rate, physicochemical behavior of active and inactive ingredients and the particle characteristics of DPI formulations are considered.

Development of an Excipient-Free Peptide Dry Powder Inhalation for the Treatment of Pulmonary Fibrosis

The caveolin scaffolding domain peptide (CSP) is being developed for the therapeutic intervention of a lethal lung disease, idiopathic pulmonary fibrosis. While direct respiratory delivery of CSP7 (a 7-mer fragment of CSP) is considered an effective route, proper formulation and processing of the peptide are required. First, air-jet milling technology was performed in order to micronize the neat peptide powder. Next, the fine particles were subjected to a stability study with physical and chemical characterizations. In addition, the in vivo efficacy of processed CSP7 powder was evaluated in an animal model of lung fibrosis. The results revealed that, with jet milling, the particle size of CSP7 was reduced to a mass median aerodynamic diameter of 1.58 ± 0.1 μm and 93.3 ± 3.3% fine particle fraction, optimal for deep lung delivery. A statistically significant reduction of collagen was observed in diseased lung tissues of mice that received CSP7 powder for inhalation. The particles remained chemically and physically stable after micronization and during storage. This work demonstrated that jet milling is effective in the manufacturing of a stable, excipient-free CSP7 inhalation powder for the treatment of pulmonary fibrosis.

Physical stability of dry powder inhaler formulations

Introduction: Dry powder inhalers (DPIs) are popular for pulmonary drug delivery. Various techniques have been employed to produce inhalation drug particles and improve the delivery efficiency of DPI formulations. Physical stability of these DPI formulations is critical to ensure the delivery of a reproducible dose to the airways over the shelf-life.Areas covered: This review focuses on the impact of solid-state stability on aerosolization performance of DPI drug particles manufactured by powder production approaches and particle-engineering techniques. It also highlights the different analytical tools that can be used to characterize the physical instability originating from production and storage.Expert opinion: A majority of the DPI literature focuses on the effects of physico-chemical properties such as size, morphology, and density on aerosolization. While little has been reported on the physical stability, particularly the stability of engineered drug particles for use in DPIs. Literature data have shown that different particle-engineering methods and storage conditions may cause physical instability of dry powders for inhalation and can significantly change the aerosol performance. A systematic examination of physical instability mechanisms in DPI formulations is necessary during formulation development in order to select the optimum formulation with satisfactory stability. In addition, the use of appropriate characterization tools is critical to detect and understand physical instability during the development of DPI formulations.

Effect of Lactose Pseudopolymorphic Transition on the Aerosolization Performance of Drug/Carrier Mixtures

Physico-chemical properties of lactose are key factors in adhesive mixtures used as dry powder inhaler (DPI). Despite the abundant literature on this topic, the effect of the polymorphism and pseudo-polymorphism of lactose has been seldom investigated and discussed although often lactose used in DPI is subjected to unit operations, which may alter its solid-state properties. Here, we studied the aerosolization performance of salbutamol sulphate (SS) or budesonide (BUD) formulations by investigating the effect of lactose pseudopolymorphism in ternary (coarse lactose/fine lactose/drug) and binary (coarse lactose/drug) mixtures. An improvement of the aerosolization performance of SS formulations with the increase of the amount of fine micronized lactose up to 30% (fine particle fraction (FPF) = 57%) was observed. Micronized lactose contained hygroscopic anhydrous α-lactose, which converted to α-lactose monohydrate at ambient conditions. This implied that the positive effect of fines on the aerosolization performance decreased and eventually disappeared with the formulation aging. Positive effect on SS deposition was observed also with binary mixtures with anhydrous lactose, whereas the opposite occurred with budesonide-containing formulations. The collected data demonstrated the crucial role of the carrier crystal form on the positive effect of fines on the deposition.

A review on recent technologies for the manufacture of pulmonary drugs

This review discusses recent developments in the manufacture of inhalable dry powder formulations. Pulmonary drugs have distinct advantages compared with other drug administration routes. However, requirements of drugs properties complicate the manufacture. Control over crystallization to make particles with the desired properties in a single step is often infeasible, which calls for micronization techniques. Although spray drying produces particles in the desired size range, a stable solid state may not be attainable. Supercritical fluids may be used as a solvent or antisolvent, which significantly reduces solvent waste. Future directions include application areas such as biopharmaceuticals for dry powder inhalers and new processing strategies to improve the control over particle formation such as continuous manufacturing with in-line process analytical technologies.

Milling and comilling Praziquantel at cryogenic and room temperatures: Assessment of the process-induced effects on drug properties

This study is a comprehensive evaluation of praziquantel (PZQ) behavior upon grinding considering the influence of milling temperature (cryogenic vs room temperature), frequency and time and presence of polymers (milled raw PZQ vs comilled PZQ/povidone and PZQ/crospovidone at 50:50 w/w) on two experimental responses (residual crystallinity and PZQ recovery). To this aim a full factorial design was set up and the responses of the experimental design were statistically assessed. The powder temperature, measured in different milling conditions, was found to increase with increasing milling frequency and time, up to a maximum recorded value of 46.9 °C (after 90 min at R.T.), for all the three powder systems. When PZQ was ground in RT environment, the recovery was 100%, independently from frequency and time of milling. Its residual crystallinity remained pronounced (>70%) upon milling, even if treated at the most severe conditions. Conversely, when the drug was milled in presence of the polymers, it showed a higher tendency to degradation and amorphysation, independently from the choice of the polymer. The use of cryogenic conditions, operating at temperatures lower than PZQ glass transition, permitted to dramatically reduce PZQ residual crystallinity when the drug was ground by itself. In the case of binary mixtures, the switch to a cryogenic environment did not affect significantly the experimental responses, but permitted to obtain a more predictable trend of both drug recovery and residual crystallinity when varying time and frequency of milling.

Powder flow analysis: A simple method to indicate the ideal amount of lactose fines in dry powder inhaler formulations

Many efforts have been made in the past to understand the function of lactose fines which are given as a ternary component to carrier-based dry powder inhaler formulations. It is undisputed that fines can significantly improve the performance of such formulations, but choosing the right amount of fines is a crucial point, because too high concentrations can have negative effects on the dispersion performance. The aim of this study was to indicate the optimal concentration of fines with a simple test method. For this purpose, mixtures with salbutamol sulfate and two different lactose carriers were prepared with a high shear mixer, measured with a FT4 powder rheometer and tested for fine particle delivery with two different inhaler devices. A correlation between the fluidization energy, measured with the aeration test set up, and the fine particle fractions (FPF) could be proven. This also applied for the aeration ratio, as well as the permeability of the powder samples. In addition, drug-free mixtures hardly differed in their rheological properties from mixtures containing the active pharmaceutical ingredient (API), which indicates that the method could be suitable for cost-saving screening trials. Furthermore, important aspects that explain the function of fines, such as the saturation of active sites, the formation of agglomerates and an increase in fluidization energy, could be shown in this study.

On the effects of blending, physicochemical properties, and their interactions on the performance of carrier-based dry powders for inhalation - A review

Blending drug and carrier powders to produce homogeneous drug-carrier adhesive mixtures is a key step in the production of dry powder inhaler (DPI) formulations. Although the blending conditions can result in different conclusions or probably change the outcome of a study entirely if being selected differently, there is a scarcity of data on the influence of blending processes on the physicochemical properties of bulk powder formulations and the follow-on effects on DPI performance. This paper provides an overview of the interactions between variables related to blending conditions (e.g. blending equipment, time, speed and sequence as well as environmental humidity) and powder physicochemical properties (e.g. size distribution, shape distribution, density, anomeric composition, electrostatic charge, surface, and bulk properties), and their effects on the performance of adhesive mixtures for inhalation in terms of drug content homogeneity, drug-carrier adhesion, and drug aerosolisation behaviour. The relevance of carrier payload, batch size and segregation was also discussed. Challenges and future directions were identified. This review therefore contributes towards a better understanding of the blending process, powder physicochemical properties, and their interlinked effects on the fundamental understanding of adhesive mixtures for inhalation. The knowledge gained is essential to ensure optimum blending and thereby controlled functionality of DPIs.

Evidence for the existence of powder sub-populations in micronized materials: aerodynamic size-fractions of aerosolized powders possess distinct physicochemical properties

Purpose

To investigate the agglomeration behaviour of the fine (<5.0 μm) and coarse (>12.8 μm) particle fractions of salmeterol xinafoate (SX) and fluticasone propionate (FP) by isolating aerodynamic size fractions and characterising their physicochemical and re-dispersal properties.

Methods

Aerodynamic fractionation was conducted using the Next Generation Impactor (NGI). Re-crystallized control particles, unfractionated and fractionated materials were characterized for particle size, morphology, crystallinity and surface energy. Re-dispersal of the particles was assessed using dry dispersion laser diffraction and NGI analysis.

Results

Aerosolized SX and FP particles deposited in the NGI as agglomerates of consistent particle/agglomerate morphology. SX particles depositing on Stages 3 and 5 had higher total surface energy than unfractionated SX, with Stage 5 particles showing the greatest surface energy heterogeneity. FP fractions had comparable surface energy distributions and bulk crystallinity but differences in surface chemistry. SX fractions demonstrated higher bulk disorder than unfractionated and re-crystallized particles. Upon aerosolization, the fractions differed in their intrinsic emission and dispersion into a fine particle fraction (<5.0 μm).

Conclusions

Micronized powders consisted of sub-populations of particles displaying distinct physicochemical and powder dispersal properties compared to the unfractionated bulk material. This may have implications for the efficiency of inhaled drug delivery.

Treating mannitol in a saturated solution of mannitol: a novel approach to modify mannitol crystals for improved drug delivery to the lungs

The aim of this study was to evaluate the influence of treatment of a promising dry powder aerosol carrier (mannitol) on the aerosolization performance of salbutamol sulphate (SS) using a novel approach: treating excess commercial carrier particles in a saturated solution of the same carrier. Commercial mannitol (CM) particles were treated with aqueous mannitol supersaturated solutions (20% and 25% w/v), under stirring, (300 rpm) for either 24h or 48 h. The results showed that particle treatment did not alter the polymorphic form of mannitol (β-mannitol); however, all treated mannitol particles demonstrated smoother surface topography and improved aerosolization performance compared to CM in dry powder inhalations. Unlike the concentration of mannitol solution used during treatment, the time of treatment to collect mannitol crystals was an essential key to modify the physical properties of mannitol and its effect on the aerosolization performance. In comparison to mannitol particles treated for 48 h, mannitol particles treated for 24h demonstrated larger size, more elongated-less regular shape, and smoother surfaces. No apparent relationship was obtained between in vitro aerosolisation behavior of SS with either mannitol particle size or shape descriptors. However, despite their larger size and more irregular-less uniformed shape, treated mannitol particles with smoother surfaces generated drug particles with smaller aerodynamic size and are expected to deliver higher amounts of drug to lower airways. The results demonstrated the potential of treating mannitol particles in aqueous solutions of the same material under controlled conditions to produce mannitol particles promising for dry powder inhaler systems. The results suggested that mannitol particle surface texture properties dominate over both particle size and particle shape of mannitol in terms of determining the aerosolization performance of mannitol.

Antisolvent crystallisation is a potential technique to prepare engineered lactose with promising aerosolisation properties: effect of saturation degree

Engineered lactose particles were prepared by anti-solvent crystallisation technique using lactose solutions with different saturation degrees. In comparison to commercial lactose, engineered lactose particles exhibited less elongated and more irregular shape (large aggregates composed of smaller sub-units), rougher surface texture, higher specific surface area, and different anomer form. Engineered lactose powders demonstrated smaller bulk density, smaller tap density, and higher porosity than commercial lactose powder. Dry powder inhaler (DPI) formulations containing engineered lactose and salbutamol sulphate as a model drug demonstrated improved drug content homogeneity and higher amounts of drug delivered to lower airway regions. Higher fine particle fraction of drug was obtained in the case of lactose powders with higher porosity, higher specific surface area and higher fine particle content (<5 μm). The results indicated that the higher the saturation degree of lactose solution used during crystallisation the smaller the specific surface area, the higher the amorphous lactose content, and the higher the β-lactose content of engineered lactose particles. Also, lactose powders obtained from lactose solution with higher degree of saturation showed higher bulk and tap densities and smaller porosity. Engineered lactose powders crystallized from lower saturation degree (20% and 30% w/v) deposited higher amounts of drug on lower airway regions. In conclusion, this study demonstrated that it is possible to prepare engineered lactose particles with favourable properties (e.g. higher fine particle fraction and better drug content homogeneity) for DPI formulations by using lactose solutions with lower degree of saturation during crystallisation process.

Conception, preparation and properties of functional carrier particles for pulmonary drug delivery

BACKGROUND

The effectiveness of aerosol therapy is significantly reduced by the mucus layer covering the airways of the tracheobronchial tree. According to the present concept, drug particles are delivered to the lung together with the functional carrier particle that facilitates both the drug transport into the lungs and the penetration of deposited particles through the mucus. The approach of manufacturing multi-component powders with mucoactive compounds and anti-asthmatic medicines (DSCG) bound together in a single particle is additionally considered.

METHODS

Powders were produced with the spray-drying technique from aqueous precursor solutions containing pure low molecular weight dextran, pure mannitol and dextran/mannitol-N-acetyl cysteine (NAC) mixtures (4:1 and 1:1). NAC has been selected for this purpose as a compound, which is known to be mucolytic. Dextran and mannitol are potentially applicable in the field of inhalation drug delivery. They have been used as stabilizers of functional carrier particles. Powders were characterized for their yield and physicochemical properties including: morphology (SEM), moisture content and thermal properties (DSC). Aerosol performance was determined with NGI impactor after standardized aerosolization of the produced powders in a commercial DPI.

RESULTS

Particle size distributions of dextran-NAC powders were characterized by high fine particle fraction (45-62%), which assures good particle deposition in the lower airways. The thermodynamic properties of the powders based on the temperature of the glass transition T(g) (50-63 °C) suggest the required stability during storage at moderate humidity.

CONCLUSIONS

Preliminary examination of the required properties of these particles confirms their potential as functional carriers for pulmonary drug delivery.

The effect of engineered mannitol-lactose mixture on dry powder inhaler performance

PURPOSE

To co-crystallise mannitol and lactose with a view to obtaining crystals with more favourable morphological features than either lactose or mannitol alone, suitable for use as carriers in formulations for dry powder inhalers (DPIs) using simultaneous engineering of lactose-mannitol mixtures.

METHODS

Mannitol and lactose individually and the two sugars with three different ratios were crystallised/co-crystallised using anti-solvent precipitation technique. Obtained crystals were sieved to separate 63-90 μm size fractions and then characterised by size, shape, density and in vitro aerosolisation performance. Solid state of crystallized samples was studied using FT-IR, XRPD and DSC.

RESULTS

At unequal ratios of mannitol to lactose, the elongated shape dominated in the crystallisation process. However, lactose exerted an opposite effect to that of mannitol by reducing elongation ratio and increasing the crystals' width and thickness. Crystallised β-lactose showed different anomers compared to commercial lactose (α-lactose monohydrate). Crystallised α-mannitol showed different polymorphic form compared to commercial mannitol (β-mannitol). Crystallised mannitol:lactose showed up to 5 transitions corresponding to α-mannitol, α-lactose monohydrate, β-lactose, 5α-/3β-lactose and 4α-/1β-lactose. In vitro deposition assessments showed that crystallised carriers produced more efficient delivery of salbutamol sulphate compared to formulations containing commercial grade carriers.

CONCLUSION

The simultaneous crystallization of lactose-mannitol can be used as a new approach to improve the performance of DPI formulations.

Advanced microscopy techniques to assess solid-state properties of inhalation medicines

Efficient control and characterisation of the physico-chemical properties of active pharmaceutical ingredients (APIs) and excipients for orally inhaled drug products (OIDPs) are critical to successful product development. Control and reduction of risk require the introduction of a material science based approach to product development and the use of advanced analytical tools in understanding how the solid-state properties of the input materials influence structure and product functionality. The key issues to be addressed, at a microscopic scale, are understanding how the critical quality attributes of input materials influence surface, interfacial and particulate interactions within OIDPs. This review offers an in-depth discussion on the use of advanced microscopy techniques in characterising of the solid-state properties of particulate materials for OIDPs. The review covers the fundamental principles of the techniques, instrumentation types, data interpretation and specific applications in relation to the product development of OIDPs.

Physico-chemical aspects of lactose for inhalation

A dry powder inhaler (DPI) is a dosage form that consists of a powder formulation in a device which is designed to deliver an active ingredient to the respiratory tract. It has been extensively investigated over the past years and several aspects relating to device and particulate delivery mechanisms have been the focal points for debate. DPI formulations may or may not contain carrier particles but whenever a carrier is included in a commercial formulation, it is almost invariably lactose monohydrate. Many physicochemical properties of the lactose carrier particles have been reported to affect the efficiency of a DPI. A number of preparation methods have been developed which have been claimed to produce lactose carriers with characteristics which lead to improved deposition. Alongside these developments, a number of characterization methods have been developed which have been reported to be useful in the measurement of key properties of the particulate ingredients. This review describes the various physicochemical characteristics of lactose, methods of manufacturing lactose particulates and their characterization.

The use of inverse gas chromatography for the study of lactose and pharmaceutical materials used in dry powder inhalers

Inverse gas chromatography (IGC) is a sensitive technique for the measurement of powder surface properties, especially surface energetics. Given the importance of these characteristics to the performance of dry powder inhaler formulations (DPIs), it is unsurprising that IGC has been applied to the study of these systems. Monitoring batch-to-batch variation and the effects of processing steps are established uses of IGC in this field and the relevant studies are discussed. A less established use of IGC is for the prediction of DPI performance. Although some groups have found a negative relationship between the dispersive surface energy of one formulation component and fine particle delivery, such studies often have a number of limitations. More complex approaches have failed to produce consistent results. Further, more carefully designed, studies are required in this area. In the final section of this article, some areas for on-going research are discussed, including the need to critically assess the best method for the calculation of the specific free energy of adsorption with pharmaceutical materials.

Lactose characteristics and the generation of the aerosol

The delivery efficiency of dry-powder products for inhalation is dependent upon the drug formulation, the inhaler device, and the inhalation technique. Dry powder formulations are generally produced by mixing the micronised drug particles with larger carrier particles. These carrier particles are commonly lactose. The aerosol performance of a powder is highly dependent on the lactose characteristics, such as particle size distribution and shape and surface properties. Because lactose is the main component in these formulations, its selection is a crucial determinant of drug deposition into the lung, as interparticle forces may be affected by the carrier-particle properties. Therefore, the purpose of this article is to review the various grades of lactose, their production, and the methods of their characterisation. The origin of their adhesive and cohesive forces and their influence on aerosol generation are described, and the impact of the physicochemical properties of lactose on carrier-drug dispersion is discussed in detail.

Improved aerosolization performance of salbutamol sulfate formulated with lactose crystallized from binary mixtures of ethanol-acetone

It has been shown that dry powder inhaler (DPI) formulations typically achieve low fine particle fractions (poor performance). A commonly held theory is that this is due, at least in part, to low levels of detachment of drug from lactose during aerosolization as a result of strong adhesion of drug particles to the carrier surfaces. Therefore, the purpose of the present study is to overcome poor aerosolization performance of DPI formulation by modification of lactose particles. Lactose particles were crystallized by adding solution in water to different ratios of binary mixtures of ethanol-acetone. The results showed that modified lactose particles had exceptional aerosolization performance that makes them superior to commercial lactose particles. Morphology assessment showed that crystallized lactose particles were less elongated, more irregular in shape, and composed of smaller primary lactose particles compared with commercial lactose. Solid-state characterization showed that commercial lactose particles were α-lactose monohydrate, whereas crystallized lactose particles were a mixture of α-lactose monohydrate and β-lactose according to the ratio of ethanol-acetone used during crystallization process. The enhanced performance could be mainly due to rougher surface and/or higher amounts of fines compared with the lactose crystallized from pure ethanol or commercial lactose.

Formation of bicalutamide nanodispersion for dissolution rate enhancement

Bicalutamide was loaded on hydrophilic excipients to form nanodispersions via a combination of anti-solvent precipitation and spray drying method. The particle size, BET surface area, contact angles and dissolution rate of the nanodispersions were analyzed. The results indicated that lactose was a suitable matrix to prevent the bicalutamide particles growth and aggregation. The lactose loaded particles had a mean size of 330 nm within a narrow distribution. X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Fourier transform infrared (FT-IR) characterization indicated the nanodispersion exhibited unchanged crystalline and chemical structure. Dissolution rate of bicalutamide nanodispersion was significantly faster than that of commercial products. It increased to 94% in 10 min while both commercial formulas Casodex and bicalutamide tablets dissolved 60% and 38% respectively at the same period. It was proposed that the enhanced dissolution rate of bicalutamide nanodispersion contribute to high surface area and well-wetted state of drug particles.

Dry powder aerosols generated by standardized entrainment tubes from drug blends with lactose monohydrate: 2. Ipratropium bromide monohydrate and fluticasone propionate

The objectives of this study were: systematic investigation of dry powder aerosol performance using standardized entrainment tubes (SETs) and lactose-based formulations with two model drugs; mechanistic evaluation of performance data by powder aerosol deaggregation equation (PADE). The drugs (IPB and FP) were prepared in sieved and milled lactose carriers (2% w/w). Aerosol studies were performed using SETs (shear stresses tau(s) = 0.624-13.143 N/m(2)) by twin-stage liquid impinger, operated at 60 L/min. PADE was applied for formulation screening. Excellent correlation was observed when PADE was adopted correlating FPF to tau(s). Higher tau(s) corresponded to higher FPF values followed by a plateau representing invariance of FPF with increasing tau(s). The R(2) values for PADE linear regression were 0.9905-0.9999. Performance described in terms of the maximum FPF (FPF(max): 15.0-37.6%) resulted in a rank order of ML-B/IPB > ML-A/IPB > SV-A/IPB > SV-B/IPB > ML-B/FP > ML-A/FP > SV-B/FP > SV-A/FP. The performance of IPB was superior to FP in all formulations. The difference in lactose monohydrate carriers was less pronounced for the FPF in IPB than in FP formulations. The novel PADE offers a robust method for evaluating aerodynamic performance of dry powder formulations within a defined tau(s) range.

Heterogeneous particle deaggregation and its implication for therapeutic aerosol performance

Aerosolization performance of dry powder blends of drugs for the treatment of asthma or chronic obstructive pulmonary diseases have been reported in three previous articles. In vitro aerosolization was performed at defined shear stresses (0.624-13.143 N/m(2)). Formulations were characterized aerodynamically and powder aerosol deaggregation equations (PADE) and corresponding linear regression analyses for pharmaceutical aerosolization were applied. Particle deaggregation is the result of overcoming fundamental forces acting at the particle interface. A new method, PADE, describing dry powder formulation performance in a shear stress range has been developed which may allow a fundamental understanding of interparticulate and surface forces. The application of PADE predicts performance efficiency and reproducibility and supports rational design of dry powder formulations. The analogy of aerosol performance with surface molecular adsorption has important implications. Expressions describing surface adsorption were intended to allow elucidation of mechanisms involving surface heterogeneity, lateral interaction, and multilayer adsorption of a variety of materials. By using a similar expression for drug aerosolization performance, it is conceivable that an analogous mechanistic approach to the evaluation of particulate systems would be possible.

Budesonide nanoparticle agglomerates as dry powder aerosols with rapid dissolution

Nanoparticle technology represents an attractive approach for formulating poorly water-soluble pulmonary medicines. Unfortunately, nanoparticle suspensions used in nebulizers or metered dose inhalers often suffer from physical instability in the form of uncontrolled agglomeration or Ostwald ripening. In addition, processing such suspensions into dry powders can yield broad particle size distributions. To address these encumbrances, a controlled nanoparticle flocculation process has been developed. Nanosuspensions of the poorly water-soluble drug budesonide were prepared by dissolving the drug in organic solvent containing surfactants followed by rapid solvent extraction in water. Different surfactants were employed to control the size and surface charge of the precipitated nanoparticles. Nanosuspensions were flocculated using leucine and lyophilized. Selected budesonide nanoparticle suspensions exhibited an average particle size ranging from approximately 160 to 230 nm, high yield and high drug content. Flocculated nanosuspensions produced micron-sized agglomerates. Freeze-drying the nanoparticle agglomerates yielded dry powders with desirable aerodynamic properties for inhalation therapy. In addition, the dissolution rates of dried nanoparticle agglomerate formulations were significantly faster than that of stock budesonide. The results of this study suggest that nanoparticle agglomerates possess the microstructure desired for lung deposition and the nanostructure to facilitate rapid dissolution of poorly water-soluble drugs.

Dry powdered aerosols of diatrizoic acid nanoparticle agglomerates as a lung contrast agent

Aerosolized contrast agents may improve the resolution of biomedical imaging modalities and enable more accurate diagnosis of lung diseases. Many iodinated compounds, such as diatrizoic acid, have been shown to be safe and useful for radiographic examination of the airways. Formulations of such compounds must be improved in order to allow imaging of the smallest airways. Here, diatrizoic acid nanoparticle agglomerates were created by assembling nanoparticles into inhalable microparticles that may augment deposition in the lung periphery. Nanoparticle agglomerates were fully characterized and safety was determined in vivo. After dry powder insufflation to rats, no acute alveolar tissue damage was observed 2h post-dose. Diatrizoic acid nanoparticle agglomerates possess the characteristics of an efficient and safe inhalable lung contrast agent.

Combination chemotherapeutic dry powder aerosols via controlled nanoparticle agglomeration

PURPOSE

To develop an aerosol system for efficient local lung delivery of chemotherapeutics where nanotechnology holds tremendous potential for developing more valuable cancer therapies. Concurrently, aerosolized chemotherapy is generating interest as a means to treat certain types of lung cancer more effectively with less systemic exposure to the compound.

METHODS

Nanoparticles of the potent anticancer drug, paclitaxel, were controllably assembled to form low density microparticles directly after preparation of the nanoparticle suspension. The amino acid, L-leucine, was used as a colloid destabilizer to drive the assembly of paclitaxel nanoparticles. A combination chemotherapy aerosol was formed by assembling the paclitaxel nanoparticles in the presence of cisplatin in solution.

RESULTS

Freeze-dried powders of the combination chemotherapy possessed desirable aerodynamic properties for inhalation. In addition, the dissolution rates of dried nanoparticle agglomerate formulations (approximately 60% to 66% after 8 h) were significantly faster than that of micronized paclitaxel powder as received (approximately 18% after 8 h). Interestingly, the presence of the water soluble cisplatin accelerated the dissolution of paclitaxel.

CONCLUSIONS

Nanoparticle agglomerates of paclitaxel alone or in combination with cisplatin may serve as effective chemotherapeutic dry powder aerosols to enable regional treatment of certain lung cancers.

Lactose composite carriers for respiratory delivery

PURPOSE

Lactose dry powder inhaler (DPI) carriers, constructed of smaller sub units (composite carriers), were evaluated to assess their potential for minimising drug-carrier adhesion, variability in drug-carrier forces and influence on drug aerosol performance from carrier-drug blends.

METHODS

Lactose carrier particles were prepared by fusing sub units of lactose (either 2, 6 or 10 microm) in saturated lactose slurry. The resultant composite particles, as well as supplied lactose, were sieve fractioned to obtain a 63-90 microm carriers. The carriers were evaluated in terms of size (laser diffraction) morphology (electron microscopy and atomic force microscopy), crystallinity and drug adhesion (colloid probe microscopy). In addition, blends containing drug and carrier were prepared and evaluated in terms of drug aerosol performance.

RESULTS

The surface morphology and physico-chemical properties of the composite carriers were significantly different. Depending on the initial primary lactose size, the composite particles could be prepared with different surface roughness. Variation in composite roughness could be related to the change in drug adhesion (via modification in contact geometry) and thus drug aerosol performance from drug-lactose blends.

CONCLUSION

Composite based carriers are a potential route to control drug-carrier adhesion forces and variability thus allowing more precise control of formulation performance.