The influence of lactose carrier on the content homogeneity and dispersibility of beclomethasone dipropionate from dry powder aerosols

New theory to explain the effect of lactose fines on the performance of adhesive mixtures for inhalation

A new theory for the dispersibility enhancing effect of excipient fines for adhesive mixtures for inhalation is presented in this paper, while at the same time the shortcomings of current hypotheses are discussed. The proposed mechanism, denoted the 'viscoelastic damping effect', states that the presence of fines particles acts to dampen the collisions between carrier particles during mixing. As a consequence, fewer fine particles are 'irreversibly' pressed into the carriers, which in turn entails a higher fine particle fraction. The mechanism was demonstrated experimentally at different levels of added lactose fines by studying the influence of processing on fine particle fraction. This approach furthermore enabled quantification of the effect. All fine particles present in the blend (APIs and excipient fines) act together to exert the damping effect. The proposed mechanism is able to explain the main body of published data, including the effect of added excipient fines, the effect of an increased drug load, and the effect of removal of carrier fines. The viscoelastic damping mechanism is general in nature and conveys a broader and more general understanding of the behavior of adhesive mixtures for inhalation.

Different Carriers for Use in Dry Powder Inhalers: Characteristics of Their Particles

In contemporary times, there has been a rise in the utilization of dry powder inhalers (DPIs) in the management of pulmonary and systemic diseases. These devices underwent a swift advancement in terms of both the equipment utilized and the formulation process. In this review, the carrier physicochemical characteristics that influence DPI performance are discussed, focusing its shape, morphology, size distribution, texture, aerodynamic diameter, density, moisture, adhesive and detachment forces between particles, fine carrier particles, and dry powder aerosolization. To promote the deposition of the active principal ingredient deep within the pulmonary system, advancements have been made in enhancing these factors and surface properties through the application of novel technologies that encompass particle engineering. So far, the most used carrier is lactose showing some advantages and disadvantages, but other substances and systems are being studied with the intention of replacing it. The final objective of this review is to analyze the physicochemical and mechanical characteristics of the different carriers or new delivery systems used in DPI formulations, whether already on the market or still under investigation. [Figure: see text].

Scientific and regulatory activities initiated by the U.S. food and drug administration to foster approvals of generic dry powder inhalers: Quality perspective

Regulatory science for generic dry powder inhalation products worldwide has evolved over the last decade. The revised draft guidance Metered Dose Inhaler (MDI) and Dry Powder Inhaler (DPI) Products - Quality Considerations [1] (Revision 1, April 2018) that FDA issued summarizes product considerations and potential critical quality attributes (CQAs). This guidance emphasizes the need to apply the principles of quality by design (QbD) and elements of pharmaceutical development discussed in the International Conference for Harmonisation of (ICH) guidelines. Research studies related to quality were used to support guidance recommendations, which preceded the first approval of a generic DPI product in the U.S. This review outlines scientific and regulatory hurdles that need to be surmounted to successfully bring a generic DPI to the market. The goal of this review focuses on relevant issues and various challenges pertaining to CMC topics of the generic DPI quality attributes. Furthermore, this review provides recommendations to abbreviated new drug application (ANDA) applicants to expedite generic approvals.

Recent developments in lactose blend formulations for carrier-based dry powder inhalation

Lactose is the most commonly used excipient in carrier-based dry powder inhalation (DPI) formulations. Numerous inhalation therapies have been developed using lactose as a carrier material. Several theories have described the role of carriers in DPI formulations. Although these theories are valuable, each DPI formulation is unique and are not described by any single theory. For each new formulation, a specific development trajectory is required, and the versatility of lactose can be exploited to optimize each formulation. In this review, recent developments in lactose-based DPI formulations are discussed. The effects of varying the material properties of lactose carrier particles, such as particle size, shape, and morphology are reviewed. Owing to the complex interactions between the particles in a formulation, processing adhesive mixtures of lactose with the active ingredient is crucial. Therefore, blending and filling processes for DPI formulations are also reviewed. While the role of ternary agents, such as magnesium stearate, has increased, lactose remains the excipient of choice in carrier-based DPI formulations. Therefore, new developments in lactose-based DPI formulations are crucial in the optimization of inhalable medicine performance.

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

INTRODUCTION

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

AREA COVERED

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

EXPERT OPINION

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

Rational Development of a Carrier-Free Dry Powder Inhalation Formulation for Respiratory Viral Infections via Quality by Design: A Drug-Drug Cocrystal of Favipiravir and Theophylline

Formulating pharmaceutical cocrystals as inhalable dosage forms represents a unique niche in effective management of respiratory infections. Favipiravir, a broad-spectrum antiviral drug with potential pharmacological activity against SARS-CoV-2, exhibits a low aqueous solubility. An ultra-high oral dose is essential, causing low patient compliance. This study reports a Quality-by-Design (QbD)-guided development of a carrier-free inhalable dry powder formulation containing a 1:1 favipiravir-theophylline (FAV-THP) cocrystal via spray drying, which may provide an alternative treatment strategy for individuals with concomitant influenza infections and chronic obstructive pulmonary disease/asthma. The cocrystal formation was confirmed by single crystal X-ray diffraction, powder X-ray diffraction, and the construction of a temperature-composition phase diagram. A three-factor, two-level, full factorial design was employed to produce the optimized formulation and study the impact of critical processing parameters on the resulting median mass aerodynamic diameter (MMAD), fine particle fraction (FPF), and crystallinity of the spray-dried FAV-THP cocrystal. In general, a lower solute concentration and feed pump rate resulted in a smaller MMAD with a higher FPF. The optimized formulation (F1) demonstrated an MMAD of 2.93 μm and an FPF of 79.3%, suitable for deep lung delivery with no in vitro cytotoxicity observed in A549 cells.

A digital workflow from crystallographic structure to single crystal particle attributes for predicting the formulation properties of terbutaline sulfate

A detailed inter-molecular (synthonic) analysis of terbutaline sulfate, an ionic addition salt for inhalation drug formulation, is related to its crystal morphology, the surface chemistry of the habit faces and hence to its crystal surface energy.

Preparation, characterization, and pharmacodynamics of insulin-loaded fumaryl diketopiperazine microparticle dry powder inhalation

Purpose: With the increase of population aging and the proportion of overweight and obese, a growing number of people are suffering from diabetes. Insulin (INS) as the most widely used hypoglycemic agent was always chosen as the most effective treatment method of diabetes. In this study, fumaryl diketopiperazine (FDKP) was used as a carrier for the pulmonary delivery of insulin.

Patients and methods: The INS-loaded FDKP microspheres (INS@FDKP-MPs) were prepared by spray drying and physicochemical properties (drug loading, particle size, flowability, moisture content, morphology, and crystalline state) were further investigated. Pharmacodynamics was investigated on diabetic model rats administrated by intratracheal insufflation.

Results: The INS-loaded FDKP microspheres show satisfied flowability and in vitro deposition with FPF 50.2% and MMAD 3.45 ± 0.13 μm, and the blood glucose level was significantly decreased. Moreover, no inflammatory reaction was observed during the safety study.

Conclusion: To sum up, the aim was to develop a non-injection system for insulin, INS@FDKP-MPs powder inhalation with high dose, low toxicity, and good lung deposition inhalation could rapidly decrease the blood glucose level without immune stimulation, which shows remarkably potential on diabetes treatment by pulmonary delivery route.

Formulation and evaluation of carrier-free dry powder inhaler containing sildenafil

Pulmonary delivery of sildenafil for the treatment of pulmonary arterial hypertension could overcome the limitations of intravenous and oral administration routes, such as poor patient compliance and systemic side effects. In this study, a carrier-free dry powder inhaler (DPI) formulation was developed, using spray drying technique and L-leucine as a dispersibility enhancer. Sildenafil citrate salt and sildenafil free base were evaluated for drug transport using a Calu-3 cell model, and their suitability for DPI production by spray drying was tested. Characteristics of the resultant carrier-free DPI powders were examined, namely crystallinity, morphology, size distribution, density, zeta potential, and aerodynamic performance. A Box-Behnken design was adopted to optimize the formulation and process conditions, including leucine amount, fraction of methanol in spraying solvent, and inlet temperature. While both sildenafil forms exhibited sufficient permeability for lung absorption, only sildenafil base resulted in DPI powders which were stable for 6 months. The introduction of leucine into the formulations effectively enhanced aerodynamic performance of the powders and particles with favorable size, shape, and density were produced. The optimal DPI formulation determined from experimental design possesses excellent aerodynamic performance with 89.39% emitted dose and 80.08% fine particle fraction, indicating the possibility of incorporating sildenafil into carrier-free DPIs for pulmonary delivery.

Dosing challenges in respiratory therapies

The pulmonary route of administration has been commonly used for local lung conditions such as asthma and chronic obstructive pulmonary disease (COPD). Recently, with the advent of new technologies available for both formulation and device design, molecules usually delivered at high doses, such as antibiotics and insulin to treat cystic fibrosis (CF) and diabetes, respectively, can now be delivered by inhalation as a dry powder. These molecules are generally delivered in milligrams instead of traditional microgram quantities. High dose delivery is most commonly achieved via dry powder inhalers (DPIs), breath activated devices designed with a formulated powder containing micronized drug with aerodynamic diameters between 1 and 5 µm. The powder formulation may also contain other excipients and/or carrier particles to improve the flowability and aerosol dispersion of the powder. A drawback with high doses is that the formulation contains a great number of fine particles, leading to a greater degree of cohesive forces, producing strongly bound agglomerates. With greater cohesive forces holding fine particles together, higher dispersion forces are needed for efficient de-agglomeration and aerosolisation. This requirement of greater dispersion forces has led to different dry powder formulations and vastly different inhaler designs. The purpose of this review is to evaluate the different formulation types, various DPI devices currently available, and how these affect the aerosolisation process and delivery of high dosed inhalable dry powder formulations to the lungs.

DPI formulations for high dose applications - Challenges and opportunities

This opinion piece gives reasons for high dose DPI applications, points out challenges and shows opportunities and possible solutions for high dose DPI. This piece of work shall set the stage for more in-depth reviews of state of the art and research papers addressing the challenges of high dose DPI which shall be included in the special issue of IJP.

A New Role of Fine Excipient Materials in Carrier-Based Dry Powder Inhalation Mixtures: Effect on Deagglomeration of Drug Particles During Mixing Revealed

The potential of fine excipient materials to improve the performance of carrier-based dry powder inhalation mixtures is well acknowledged. The mechanisms underlying this potential are, however, open to question till date. Elaborate understanding of these mechanisms is a requisite for rational rather than empirical development of ternary dry powder inhalation mixtures. While effects of fine excipient materials on drug adhesion to and detachment from surfaces of carrier particle have been extensively investigated, effects on other processes, such as carrier-drug mixing, capsule/blister/device filling, or aerosolization in inhaler devices, have received little attention. We investigated the influence of fine excipient materials on the outcome of the carrier-drug mixing process. We studied the dispersibility of micronized fluticasone propionate particles after mixing with α-lactose monohydrate blends comprising different fine particle concentrations. Increasing the fine (D < 10.0 μm) excipient fraction from 1.84 to 8.70% v/v increased the respirable drug fraction in the excipient-drug mixture from 56.42 to 67.80% v/v (p < 0.05). The results suggest that low concentrations of fine excipient particles bind to active sites on and fill deep crevices in coarse carrier particles. As the concentration of fine excipient particles increases beyond that saturating active sites, they fill the spaces between and adhere to the surfaces of coarse carrier particles, creating projections and micropores. They thereby promote deagglomeration of drug particles during carrier-drug mixing. The findings pave the way for a comprehensive understanding of contributions of fine excipient materials to the performance of carrier-based dry powder inhalation mixtures.

Macro-Raman spectroscopy for bulk composition and homogeneity analysis of multi-component pharmaceutical powders

A new macro-Raman system equipped with a motorized translational sample stage and low-frequency shift capabilities was developed for bulk composition and homogeneity analysis of multi-component pharmaceutical powders. Different sampling methods including single spot and scanning measurement were compared. It was found that increasing sample volumes significantly improved the precision of quantitative composition analysis, especially for poorly mixed powders. The multi-pass cavity of the macro-Raman system increased effective sample volumes by 20 times from the sample volume defined by the collection optics, i.e., from 0.02μL to about 0.4μL. A stochastic model simulating the random sampling process of polydisperse microparticles was used to predict the sampling errors for a specific sample volume. Comparison of fluticasone propionate mass fractions of the commercial products Flixotide^® 250 and Seretide^® 500 simulated for different sampling volumes with experimentally measured compositions verified that the effective sample volume of a single point macro-Raman measurement in the multi-pass cavity of this instrument was between 0.3μL and 0.5μL. The macro-Raman system was also successfully used for blend uniformity analysis. It was concluded that demixing occurred in the binary mixture of l-leucine and d-mannitol from the observation that the sampling errors indicated by the standard deviations of measured leucine mass fractions increased during mixing, and the standard deviation values were all larger than the theoretical lower limit determined by the simulation. Since sample volume was shown to have a significant impact on measured homogeneity characteristics, it was concluded that powder homogeneity analysis results, i.e., the mean of individual test results and absolute and relative standard deviations, must be presented together with the effective sample volumes of the applied testing techniques for any measurement of powder homogeneity to be fully meaningful.

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.

Proliposome powders prepared using a slurry method for the generation of beclometasone dipropionate liposomes

A novel "slurry method" was described for the preparation of proliposome powders using soya phosphatidylcholine (SPC) with cholesterol (1:1) and for incorporation of beclometasone dipropionate (BDP) at 2mole% of the total lipid phase. Proliposomes made with a range of lipid to sucrose carrier ratios were studied in terms of surface morphology using scanning electron microscopy (SEM) and thermal properties using differential scanning calorimetry (DSC). Following hydration of proliposomes, the resultant vesicles were compared to liposomes made using the traditional proliposome method, in terms of vesicle size and drug entrapment efficiency. SEM showed that sucrose was uniformly coated with lipid regardless of lipid to carrier ratio. Liposomes generated using the slurry proliposome method tended to have smaller median size than those generated with the conventional proliposome method, being in the range of 4.72-5.20μm and 5.89-7.72μm respectively. Following centrifugation of liposomes using deuterium oxide (D2O) as dispersion medium, vesicles entrapping BDP were separated as a floating creamy layer, whilst the free drug was sedimented as crystals. Drug entrapment was dependent on formulation composition and preparation method. When 1:15 w/w lipid to carrier was used, liposomes generated using the slurry method had an entrapment efficiency of 47.05% compared to 18.67% for those generated using the conventional proliposome method. By contrast, liposomes made by the thin-film hydration method had an entrapment efficiency of 25.66%. DSC studies using 50mole% BDP demonstrated that the drug was amorphous in the proliposome formulation and tended to crystallize on hydration, resulting in low drug entrapment. In conclusion, a novel approach to the preparation of proliposomes using a slurry method has been introduced, offering higher entrapment for BDP than liposomes made using the conventional proliposome method and those prepared by thin-film hydration technique.

Feasibility of highly branched cyclic dextrin as an excipient matrix in dry powder inhalers

We investigated the feasibility of highly branched cyclic dextrin (HBCD) as an excipient matrix in dry powder inhalers (DPIs). The fine particles of HBCD and HBCD/active pharmaceutical ingredients (APIs) were prepared by spray-drying an ethanol-aqueous solution containing HBCD. The particle size of spray-dried HBCD itself was approximately 3.0μm with a wrinkled shape. Solid-state fluorescence emission spectroscopy of 1-naphthoic acid (1-NPA) showed that it was dispersed in a molecular dispersion/solid solution, if the model compound of 1-NPA was spray-dried with HBCD. Powder X-ray diffraction and differential scanning calorimetry indicate that 1-NPA was in the amorphous state after spray-drying with HBCD, which is confirmed by the fluorescence measurements, 1-NPA could be incorporated into HBCD. When the antimycobacterial agent, rifampicin, was spray-dried with HBCD for the purpose of pulmonary administration, the emitted dose and fine-particle fraction of the spray-dried particles of rifampicin with HBCD were 95.7±1.7% and 39.5±5.7%, respectively. The results indicated that HBCD possessed a high potential as an excipient in DPIs, not only by molecular association of API molecules with HBCD, but also by that of API fine crystals.

Influence of surface characteristics of modified glass beads as model carriers in dry powder inhalers (DPIs) on the aerosolization performance

The aim of this work is to investigate the effect of surface characteristics (surface roughness and specific surface area) of surface-modified glass beads as model carriers in dry powder inhalers (DPIs) on the aerosolization, and thus, the in vitro respirable fraction often referred to as fine particle fraction (FPF). By processing glass beads in a ball mill with different grinding materials (quartz and tungsten carbide) and varying grinding time (4 h and 8 h), and by plasma etching for 1 min, glass beads with different shades of surface roughness and increased surface area were prepared. Compared with untreated glass beads, the surface-modified rough glass beads show increased FPFs. The drug detachment from the modified glass beads is also more reproducible than from untreated glass beads indicated by lower standard deviations for the FPFs of the modified glass beads. Moreover, the FPF of the modified glass beads correlates with their surface characteristics. The higher the surface roughness and the higher the specific surface area of the glass beads the higher is the FPF. Thus, surface-modified glass beads make an ideal carrier for tailoring the performance of DPIs in the therapy of asthma and chronically obstructive pulmonary diseases.

Dry powders for oral inhalation free of lactose carrier particles

Dry powder inhaler (DPI) products have traditionally comprised a simple formulation of micronised drug mixed with a carrier excipient, typically lactose monohydrate. The presence of the carrier is aimed at overcoming issues of poor flowability and dispersibility, associated with the cohesive nature of small, micronised active pharmaceutical ingredient (API) particles. Both the powder blend and the DPI device must be carefully designed so as to ensure detachment of the micronised drug from the carrier excipient on inhalation. Over the last two decades there has been a significant body of research undertaken on the design of carrier-free formulations for DPI products. Many of these formulations are based on sophisticated particle engineering techniques; a common aim in formulation design of carrier-free products being to reduce the intrinsic cohesion of the particles, while maximising dispersion and delivery from the inhaler. In tandem with the development of alternative formulations has been the development of devices designed to ensure the efficient delivery and dispersion of carrier-free powder on inhalation. In this review we examine approaches to both the powder formulation and inhaler design for carrier-free DPI products.

Alternative carriers in dry powder inhaler formulations

The aerosolization efficiency of a powder is highly dependent on carrier characteristics, such as particle size distribution, shape and surface properties. The main objective in the inhalation field is to achieve a high and reproducible pulmonary deposition. This can be provided by successful carrier selection and careful process optimization for carrier modification. Lactose is the most common and frequently used carrier in dry powder inhaler (DPI) formulations. But lactose shows some limitations in formulation with certain drugs and peptides that prohibit its usage as a carrier in DPI formulations. Here, we criticality review the most important alternative carriers to lactose with merits, demerits and applications in DPI formulations.

[Inhalation therapy: inhaled corticosteroids in ENT, development and technical challenges of powder inhalers, nebulisers synchronized with breathing and aerosol size distribution. GAT aerosolstorming, Paris 2012]

The working group on aerosol therapy (GAT) of the Société de Pneumologie de Langue Française (SPLF) has organized its third Aerosolstorming in 2012. During one single day, different aspects of inhaled therapies have been treated and are detailed in two articles, this one being the second. This text deals with the indications of inhaled corticosteroids in ENT, the development and technical challenges of powder inhalers, the advantages and disadvantages of each type of technologies to measure the particle sizes of inhaled treatments.

Rapid characterisation of the inherent dispersibility of respirable powders using dry dispersion laser diffraction

Understanding and controlling powder de-agglomeration is of great importance in the development of dry powder inhaler (DPI) products. Dry dispersion laser diffraction measures particle size readily under controlled dispersing conditions, but has not been exploited fully to characterise inherent powder dispersibility. The aim of the study was to utilise particle size-dispersing pressure titration curves to characterise powder cohesivity and ease of de-agglomeration. Seven inhaled drug/excipient powders (beclometasone dipropionate, budesonide, fluticasone propionate, lactohale 300, salbutamol base, salmeterol xinafoate and tofimilast) were subjected to a range of dispersing pressures (0.2-4.5 Bar) in the Sympatec HELOS/RODOS laser diffractometer and particle size measurements were recorded. Particle size-primary pressure data were used to determine the pressures required for complete de-agglomeration. The latter were employed as an index of the cohesive strength of the powder (critical primary pressure; CPP), and the curves were modelled empirically to derive the pressure required for 50% de-agglomeration (DA₅₀). The powders presented a range of CPP (1.0-3.5 Bar) and DA₅₀ (0.23-1.45 Bar) which appeared to be characteristic for different mechanisms of powder de-agglomeration. This approach has utility as a rapid pre-formulation tool to measure inherent powder dispersibility, in order to direct the development strategy of DPI products.

Lactose engineering for better performance in dry powder inhalers

Dry powder inhaler (DPI) is generally formulated as a powder mixture of coarse carrier particles and micronized drug with aerodynamic diameters of 1-5 μm. Carrier particles are used to improve drug particle flowability, thus improving dosing accuracy, minimizing the dose variability compared with drug alone and making them easier to handle during manufacturing operations. Lactose is the most common and frequently used carrier in DPIs formulations and nowadays various inhalation grades of lactose with different physico-chemical properties are available on the market. Therefore, the purpose of this manuscript is to review evolution of lactose as a carrier in inhalable formulations, their production and the impact of its physico-chemical properties on drug dispersion. This review offers a perspective on the current reported studies to modify lactose for better performance in DPIs.

Dry powder inhalers: study of the parameters influencing adhesion and dispersion of fluticasone propionate

Interactions between particles are dependent on the physicochemical characteristics of the interacting particles but it is also important to consider the manufacturing process. Blending active pharmaceutical ingredient (API) with carrier is a critical stage that determines the blend homogeneity and is the first step towards obtaining the final quality of the powder blend. The aim of this work was to study parameters that influence the interactions between API and carrier in adhesive mixtures used in DPI and their effect on API dispersion. The study was done with fluticasone propionate blended with lactose 'Lactohale 200'. The study was based on the influence of the operating conditions (speed, mixing time, resting steps during mixing), the size of the carrier and the storage conditions on the blend properties and on the API dispersion. The quality of the blends was examined by analysing the API content uniformity. Adhesion characteristics were evaluated by submitting mixtures to a sieving action by air depression with the Alpine air-jet sieve. Aerodynamic evaluation of fine particle fraction (FPF) was obtained using a Twin Stage Impinger; the FPF being defined as the mass percentage of API below 6.4 μm. For good dispersion and therefore good homogeneity of the API in the carrier particles, speed and powder blending time have to be sufficient, but not too long to prevent the appearance of static electricity, which is not favourable to homogeneity and stability. The FPF increases with the decrease in the carrier size. The storage conditions have also to be taken into consideration. Higher humidity favours the adhesion of API on the carrier and decreases the FPF.

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.

A critical view on lactose-based drug formulation and device studies for dry powder inhalation: which are relevant and what interactions to expect?

Many years of research have not led to a profound knowledge of the mechanisms involved in the formulation and dispersion of carrier based mixtures for inhalation. Although it is well understood that the mixing is a key process in DPI carrier based formulation, there remains a limited understanding of how blending processes affect in-process material properties and the resulting distribution of the drug in the final dosage form. A great number of variables are considered relevant to the interfacial forces in adhesive mixtures, but their effects have mostly been investigated individually, without taking account of the influence they may have on each other. Interactions may be expected and without proper choices made and definitions given for all the variables involved, conclusions from studies on adhesive mixtures are of less relevance. By varying any of the variables that are not subject of the study, an opposite effect may be obtained. Currently, there is a strong focus on exploring techniques for the characterisation of drug and carrier surface properties that are believed to have an influence on the interparticulate forces in adhesive mixtures. For a number of surface properties it may be questioned whether they are really the key parameters to investigate however. Their orders of magnitude are subordinate to the effects they are supposed to have on the drug-to-carrier forces. Therefore, they seem rather indicators of other variability and their influence may be dominated by other effects. Finally, the relevance of inhaler design is often ignored. By using powerful inhalers, the effect of many variables of current concern may become less relevant. Carrier properties that are considered disadvantageous at present may even become desirable when a more appropriate type of dispersion force is applied. This can be shown for the effect of carrier surface rugosity when inertial separation forces are applied instead of the more widely applied lift and drag forces. Therefore, inhaler design should be taken into consideration when evaluating studies on adhesive mixtures. It should also become an integral part of powder formulation for inhalation.

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.

Investigation into alternative sugars as potential carriers for dry powder formulation of budesonide

INTRODUCTION

Dry powder inhaler (DPI) formulations are so far being used for pulmonary drug delivery, mainly for the treatment of asthma and chronic obstructive pulmonary disease (COPD). Currently most of DPI formulations rely on lactose as a carrier in the drug powder blend. However, due to reducing sugar function of lactose which makes it incompatible with some drugs such as budesonide, it is realistic to investigate for alternative sugars that would overcome the concerned drawback but still have the positive aspects of lactose.

METHODS

The study was conducted by characterizing carriers for their physico-chemical properties and preparing drug/carrier blends with concentration of 5% and 10% drug with the carrier. The mixing uniformity (homogeneity) of Budesonide in the blends was analyzed using spectrophotometer. The blend was then filled into NB7/2 Airmax inhaler device and the deposition profiles of the drug were determined using multi stage liquid impinger (MSLI) after aerosolization at 4 kPa via the inhaler. The morphology of the carriers conducted using the scanning electron microscope.

RESULTS

The results determined that the mean fine particle fraction (FPF) of 5% and 10% blends of mannitol was 61%, possibly due to fine elongated particles. Dextrose exhibited excellent flowability. Scanning electron microscope illustrated mannitol with fine elongated particles and dextrose presenting larger and coarse particles. It was found out that type of carriers, particle size distribution, and morphology would influence the FPF of budesonide.

CONCLUSION

It may be concluded that mannitol could be suitable as a carrier on the basis of its pharmaceutical performance and successful achievement of FPF whereas the more hygroscopic sugars such as sorbitol or xylitol showed poor dispersibility leading to lower FPF.

Characterisation and deposition studies of recrystallised lactose from binary mixtures of ethanol/butanol for improved drug delivery from dry powder inhalers

Dry powder inhaler formulations comprising commercial lactose-drug blends can show restricted detachment of drug from lactose during aerosolisation, which can lead to poor fine particle fractions (FPFs) which are suboptimal. The aim of the present study was to investigate whether the crystallisation of lactose from different ethanol/butanol co-solvent mixtures could be employed as a method of altering the FPF of salbutamol sulphate from powder blends. Lactose particles were prepared by an anti-solvent recrystallisation process using various ratios of the two solvents. Crystallised lactose or commercial lactose was mixed with salbutamol sulphate and in vitro deposition studies were performed using a multistage liquid impinger. Solid-state characterisation results showed that commercial lactose was primarily composed of the α-anomer whilst the crystallised lactose samples comprised a α/β mixture containing a lower number of moles of water per mole of lactose compared to the commercial lactose. The crystallised lactose particles were also less elongated and more irregular in shape with rougher surfaces. Formulation blends containing crystallised lactose showed better aerosolisation performance and dose uniformity when compared to commercial lactose. The highest FPF of salbutamol sulphate (38.0 ± 2.5%) was obtained for the lactose samples that were crystallised from a mixture of ethanol/butanol (20:60) compared to a FPF of 19.7 ± 1.9% obtained for commercial lactose. Engineered lactose carriers with modified anomer content and physicochemical properties, when compared to the commercial grade, produced formulations which generated a high FPF.

Engineered mannitol as an alternative carrier to enhance deep lung penetration of salbutamol sulphate from dry powder inhaler

In this research mannitol particles were prepared by recrystallisation using non-solvent precipitation technique to investigate the effect of engineered carrier particles on their physicochemical properties and the in vitro deposition profiles of a model drug (salbutamol sulphate (SS)) from a dry powder inhaler (DPI). To this end, mannitol aqueous solution (15%, w/v) was added to different ratios of ethanol:water (100:0, 95:5, 90:10 and 85:15) to obtain mannitol particles. These crystallised mannitol particles were analysed in terms of micromeritic properties, morphology, DSC, FT-IR, and in vitro fine particle fraction (FPF) and emitted dose (ED) of SS. The results showed that the elongation ratio of all the recrystallised mannitol batches was higher than the original material giving them a needle-shaped morphology. Salbutamol sulphate deposition profiles from DPI formulation containing recrystallised needle-shaped mannitol showed enhanced performance and better delivery to the lower MSLI stages. The FPF increased from 15.4+/-1.1 to 45.8+/-0.7% when the commercial mannitol was replaced by mannitol crystallised from ethanol:water (90:10). This improvement could be due to the presence of elongated mannitol crystals in formulation blends. Solid state characterisation of engineered mannitol showed that the commercial mannitol was beta-form, mannitol recrystallised from ethanol:water (85:15) was alpha-form and that samples recrystallised in presence of pure ethanol or other ratios of ethanol:water (95:5 and 90:10) were the mixtures of alpha-, beta- and delta-forms. Multi-solvent recrystallisation technique was proved to have potential to produce mannitol crystals suitable for enhanced aerosolisation efficiency. Comparing different crystallised mannitol formulations showed that the final form (the type of polymorph) of the crystallised mannitol does not have a substantial effect on salbutamol sulphate aerosolisation performance.

Influence of fines on the surface energy heterogeneity of lactose for pulmonary drug delivery

The effects of the blending of lactose fines to the overall adhesion property of coarse alpha-lactose monohydrate carrier particles were investigated. Five samples, three of them commercial samples from DOMO (Lactohale) LH100, LH210, and LH250) whilst the other two are blends of LH210 and LH250, were studied. Characterisation included particle sizing, SEM, PXRD and IGC. Dispersive surface energy gamma(SV)(d) was determined using a finite concentration IGC method to obtain a distribution profile. The gamma(SV)(d) distribution of lactose crystals was found to vary from 40 to 48mJ/m(2). The unmilled coarse crystalline lactose sample (LH100) gamma(SV)(d) was lowest and showed less heterogeneity than the milled sample (LH250). Fines (LH210) were found to have the highest gamma(SV)(d) value. The samples with loaded LH210 were found to have a higher energy than LH100. The amount of LH210 in Blend 1 was not able to decrease surface energy heterogeneity, whereas sample Blend 2 showed adequate loading of fines to obtain a relatively homogeneous surface. Addition of fines resulted in an increase in gamma(SV)(d), suggesting that coarse lactose surfaces were replaced by surfaces of the fines. Increasing the loading of fines may result in a more homogeneous surface energy of lactose particles.

Influence of the polydispersity of the added fine lactose on the dispersion of salmeterol xinafoate from mixtures for inhalation

The purpose of this study was to determine and understand the effect of the polydispersity of fine lactose (FL) on the dispersion of salmeterol xinafoate (SX) from SX-coarse lactose mixtures for inhalation. SX mixtures were prepared using validated laboratory mixing. The in vitro deposition of SX was measured using a twin-stage impinger and SX analysed using high performance liquid chromatography. The distributions of FL included both cohesive to non-cohesive fractions. Reduction in the span of the FL distributions with a volume median diameters (VMD) about 7 microm showed no significant difference in the fine particle fraction (FPF) of SX (P > 0.05), while reduced FPF of SX was observed with the reduction in the span of FL with VMD about 19 and 32 microm, respectively. When the FPF of SX was correlated with the concentration of FL in specific fractions, there was a marked, linear increase in FPF for increasing concentrations of FL in the 5-10 microm fraction; however, all other fractions showed no significant increase in FPF. The study reflects the importance of lactose polydispersity in drug dispersion. Specific size fractions of cohesive FL enhance dispersion, while non-cohesive fractions of FL act as secondary carriers and decrease dispersion performance.