Pharmacokinetic Study of Fingolimod Nasal Films Administered via Nose-to-Brain Route in C57BL/6 J Mice as Potential Treatment for Multiple Sclerosis.

BACKGROUND: Fingolimod hydrochloride (FH) has emerged as a vital medication for managing Multiple Sclerosis (MS). Despite its high oral bioavailability of 93%, it is plagued by slow oral absorption (Tmax = 8-12 h) and extensive hepatic metabolism. Intranasal administration has emerged as an alternative to address these limitations, ensuring efficient central nervous system delivery and minimizing peripheral exposure and first-pass metabolism. OBJECTIVE: This study aims to develop and evaluate FH nasal films for enhanced drug delivery. METHODS: A Design of Experiments approach was employed to formulate FH nasal films, utilizing HPMC E50 as a film-forming polymer, PEG 400 as a plasticizer, and Me-ß-CD as a permeation enhancer. Two formulations with superior in vitro and ex vivo performance were selected for in vivo evaluation. A comparative pharmacokinetic study was conducted in C57BL/6 J mice in the brain and serum after administration of nasal films and oral FH solution, respectively. Sparse sampling and non-compartmental analysis were used. RESULTS: FH nasal films efficiently delivered the drug to both serum (Cmax(F3) = 0.35 ± 0.021, Cmax(F4) = 0.38 ± 0.029 µg/mL) and brain (Cmax(F3) = 0.39 ± 0.05, Cmax(F4) = 0.44 ± 0.048 µg/mL), achieving higher levels than oral delivery. Brain relative bioavailability (% Frel (0-6 h)) was 519% and 534%, while serum % Frel (0-6 h) was 295% and 343%. CONCLUSIONS: The rapid nose-to-brain delivery within 30 min, in contrast to 10-h Tmax of the oral solution, indicates the potential of a combined IN and oral treatment regimen. This approach could expedite the attainment of steady-state concentrations, offering a promising method for managing multiple sclerosis (MS).

Development and Pharmacokinetics of a Novel Acetylsalicylic Acid Dry Powder for Pulmonary Administration.

Aspirin is an historic blockbuster product, and it has been proposed in a wide range of formulas. Due to exacerbation risks, the pulmonary route has been seldom considered as an alternative to conventional treatments. Only recently, owing to overt advantages, inhalable acetylsalicylic acid dry powders (ASA DPI) began to be considered as an option. In this work, we developed a novel highly performing inhalable ASA DPI using a nano spray-drying technique and leucine as an excipient and evaluated its pharmacokinetics compared with oral administration. The formulation obtained showed remarkable respirability and quality features. Serum and lung ASA DPI profiles showed faster presentation in blood and higher retention compared with oral administration. The dry powder was superior to the DPI suspension. The relative bioavailability in serum and lungs claimed superiority of ASA DPI over oral administration, notwithstanding a fourfold lower pulmonary dose. The obtained ASA DPI formulation shows promising features for the treatment of inflammatory and infectious lung pathologies.

Development and In Vitro-Ex Vivo Evaluation of Novel Polymeric Nasal Donepezil Films for Potential Use in Alzheimer's Disease Using Experimental Design.

The objective and novelty of the present study is the development and optimization of innovative nasal film of Donepezil hydrochloride (DH) for potential use in Alzheimer's disease. Hydroxypropyl-methyl-cellulose E50 (factor A) nasal films, with Polyethylene glycol 400 as plasticizer (factor B), and Methyl-ß-Cyclodextrin, as permeation enhancer (factor C), were prepared and characterized in vitro and ex vivo. An experimental design was used to determine the effects of the selected factors on permeation profile of DH through rabbit nasal mucosa (response 1), and on film flexibility/foldability (response 2). A face centered central composite design with three levels was applied and 17 experiments were performed in triplicate. The prepared films exhibited good uniformity of DH content (90.0 ± 1.6%−99.8 ± 4.9%) and thickness (19.6 ± 1.9−170.8 ± 11.5 µm), storage stability characteristics, and % residual humidity (<3%), as well as favourable swelling and mucoadhesive properties. Response surface methodology determined the optimum composition for flexible nasal film with maximized DH permeation. All selected factors interacted with each other and the effect of these interactions on responses is strongly related to the factor's concentration ratios. Based on these encouraging results, in vivo serum and brain pharmacokinetic study of the optimized nasal film, in comparison to DH oral administration, is ongoing in an animal model.

Design of a Personalized Nasal Device (Matrix-Piston Nasal Device, MPD) for Drug Delivery: a 3D-Printing Application.

The purpose of the current study is the development and the in vitro evaluation of a novel device for the nasal delivery of biodegradable polymeric films. The Matrix-Piston nasal Device (MPD) was designed and then printed employing Fused Deposition Modeling. Particularly, the CAD model of MPD was produced considering the human anatomical features of the nasal cavity and aiming to deliver the formulation on the olfactory region. The device consists of two independent parts constructed by different materials. For the 3D-printing process, different materials were tested to decide the most applicable for each part. More precisely, Thermoplastic Polyurethene (TPU) polymer was selected to print the matrix, while Acrylonitrile Butadiene Styrene (ABS) for the piston. Furthermore, two nasal casts were printed to be used for the assessment of the device. Namely, an hydroxypropyl-methyl cellulose-based drug-free film, containing polyethylene glycol 400 as plasticizer and methyl-ß-cyclodextrin as permeation enhancer, was formed on the MPD to be tested for its ability to be detached from the device and positioned on the artificial olfactory region of the nasal cast. The deposition of the film on the targeted area of the semi-realistic nasal cast took place successfully.

Inhalable Microparticles Embedding Calcium Phosphate Nanoparticles for Heart Targeting: The Formulation Experimental Design.

Inhalation of Calcium Phosphate nanoparticles (CaPs) has recently unmasked the potential of this nanomedicine for a respiratory lung-to-heart drug delivery targeting the myocardial cells. In this work, we investigated the development of a novel highly respirable dry powder embedding crystalline CaPs. Mannitol was selected as water soluble matrix excipient for constructing respirable dry microparticles by spray drying technique. A Quality by Design approach was applied for understanding the effect of the feed composition and spraying feed rate on typical quality attributes of inhalation powders. The in vitro aerodynamic behaviour of powders was evaluated using a medium resistance device. The inner structure and morphology of generated microparticles were also studied. The 1:4 ratio of CaPs/mannitol led to the generation of hollow microparticles, with the best aerodynamic performance. After microparticle dissolution, the released nanoparticles kept their original size.

Dry Powder Inhalers in the Digitalization Era: Current Status and Future Perspectives.

During the last decades, the term "drug delivery systems" (DDSs) has almost fully replaced previously used terms, such as "dosage forms", in an attempt to emphasize the importance of the drug carrier in ensuring the claimed safety and effectiveness of the product. However, particularly in the case of delivery devices, the term "system", which by definition implies a profound knowledge of each single part and their interactions, is not always fully justified when using the DDS term. Within this context, dry powder inhalers (DPIs), as systems to deliver drugs via inhalation to the lungs, require a deep understanding of the complex formulation-device-patient interplay. As of now and despite the progress made in particle engineering and devices design, DPIs' clinical performance is limited by variable patients' breathing patterns. To circumvent this pitfall, next-generation DPIs should ideally adapt to the different respiratory capacity of individuals across age, health conditions, and other related factors. In this context, the recent wave of digitalization in the health care and industrial sectors may drive DPI technology towards addressing a personalized device-formulation-patient liaison. In this review, evolving technologies are explored and analyzed to outline the progress made as well as the gaps to fill to align novel DPIs technologies with the systems theory approach.

Nasal powders of quercetin-ß-cyclodextrin derivatives complexes with mannitol/lecithin microparticles for Nose-to-Brain delivery: In vitro and ex vivo evaluation.

Quercetin, a flavonoid with possible neuroprotective action has been recently suggested for the early-stage treatment of Alzheimer's disease. The low solubility and extended first pass effect render quercetin unsuitable for oral administration. Alternatively, brain targeting is more feasible with nasal delivery, by-passing, non-invasively, Blood-Brain Barrier and ensuring rapid onset of action. Aiming to increase quercetin's disposition into brain, nasal powders consisting of quercetin-cyclodextrins (methyl-ß-cyclodextrin and hydroxypropyl-ß-cyclodextrin) lyophilizates blended with spray-dried microparticles of mannitol/lecithin were prepared. Quercetin's solubility at 37 °C and pH 7.4 was increased 19-35 times when complexed with cyclodextrins. Blending lyophilizates in various ratios with mannitol/lecithin microparticles, results in powders with improved morphological characteristics as observed by X-ray Diffraction and Scanning Electron Microscopy analysis. In vitro characterization of these powders using Franz cells, revealed rapid dissolution and permeation 17 (methyl-ß-cyclodextrin) to 48 (hydroxypropyl-ß-cyclodextrin) times higher than that of pure quercetin. Ex vivo powders' transport across rabbit nasal mucosa was found more efficient in comparison with the pure Que. The overall better performance of quercetin-hydroxypropyl-ß-cyclodextrin powders is confirmed by ex vivo experiments revealing amount of quercetin permeated ranging from 0.03 ± 0.01 to 0.22 ± 0.05 µg/cm2 for hydroxypropyl-ß-cyclodextrin and 0.022 ± 0.01 to 0.17 ± 0.04 µg/cm2 for methyl-ß-cyclodextrin powders, while the permeation of pure quercetin was negligible.

Flurbiprofen sodium microparticles and soft pellets for nose-to-brain delivery: Serum and brain levels in rats after nasal insufflation.

Neuroinflammation in Alzheimer's disease (AD) revamped the role of a preventive therapeutic action of non steroidal anti-inflammatory drugs; flurbiprofen could delay AD onset, provided its access to brain is enhanced and systemic exposure limited. Nasal administration could enable direct drug access to central nervous system (CNS) via nose-to-brain transport. Here, we investigated the insufflation, deposition, dissolution, transmucosal permeation, and in vivo transport to rat brain of flurbiprofen from nasal powders combined in an active device. Flurbiprofen sodium spray-dried microparticles as such, or soft pellets obtained by agglomeration of drug microparticles with excipients, were intranasally administered to rats by the pre-metered insufflator device. Blood and brain were collected to measure flurbiprofen levels. Excipient presence in soft pellets lowered the metered drug dose to insufflate. Nevertheless, efficiency of powder delivery by the device, measured as emitted fraction, was superior with soft pellets than microparticles, due to their coarse size. Both nasal powders resulted into rapid flurbiprofen absorption. Absolute bioavailability was 33% and 58% for microparticles and pellets, respectively. Compared to intravenous flurbiprofen, the microparticles were more efficient than soft pellets at enhancing direct drug transport to CNS. Direct Transport Percentage index evidenced that more than 60% of the intranasal dose reached the brain via direct nose-to-brain transport for both powders. Moreover, remarkable drug concentrations were measured in the olfactory bulb after microparticle delivery. Bulb connection with the entorhinal cortex, from where AD initiates, makes flurbiprofen sodium administration as nasal powder worth of further investigation in an animal model of neuroinflammation.

Preparation and Biophysical Characterization of Quercetin Inclusion Complexes with ß-Cyclodextrin Derivatives to be Formulated as Possible Nose-to-Brain Quercetin Delivery Systems.

Quercetin (Que) is a flavonoid associated with high oxygen radical scavenging activity and potential neuroprotective activity against Alzheimer's disease. Que's oral bioavailability is limited by its low water solubility and extended peripheral metabolism; thus, nasal administration may be a promising alternative to achieve effective Que concentrations in the brain. The formation of Que-2-hydroxypropylated-ß-cyclodextrin (Que/HP-ß-CD) complexes was previously found to increase the molecule's solubility and stability in aqueous media. Que-methyl-ß-cyclodextrin (Que/Me-ß-CD) inclusion complexes were prepared, characterized, and compared with the Que/HP-ß-CD complex using biophysical and computational methods (phase solubility, fluorescence and NMR spectroscopy, differential scanning calorimetry (DSC), and molecular dynamics simulations (MDS)) as candidates for the preparation of nose-to-brain Que's delivery systems. DSC thermograms, NMR, fluorescence spectroscopy, and MDS confirmed the inclusion complex formation of Que with both CDs. Differences between the two preparations were observed regarding their thermodynamic stability and inclusion mode governing the details of molecular interactions. Que's solubility in aqueous media at pH 1.2 and 4.5 was similar and linearly increased with both CD concentrations. At pH 6.8, Que's solubility was higher and positively deviated from linearity in the presence of HP-ß-CD more than with Me-ß-CD, possibly revealing the presence of more than one HP-ß-CD molecule involved in the complex. Overall, water solubility of lyophilized Que/Me-ß-CD and Que/HP-ß-CD products was approximately 7-40 times and 14-50 times as high as for pure Que at pH 1.2-6.8. In addition, the proof of concept experiment on ex vivo permeation across rabbit nasal mucosa revealed measurable and similar Que permeability profiles with both CDs and negligible permeation of pure Que. These results are quite encouraging for further ex vivo and in vivo evaluation toward nasal administration and nose-to-brain delivery of Que.

Partial tablet coating by 3D printing.

In the last decade 3D printing (3DP) technology has gained increasing interest in the pharmaceutical field addressing several novel challenges such as on-demand manufacturing at the point of need, customization of drug release profiles and patient-specific solutions as well as combinations of several APIs in one dosage form. Therefore, 3DP can become a new and promising path to drug product development and manufacturing, able to support specific therapies and improve compliance, safety and effectiveness. The aim of this work was to partially coat tablets with a glyceride, namely Precirol ATO 5 using a semi-solids 3D printer as an approach for tuning the release of two Active Pharmaceutical Ingredients (APIs), the hydrophilic methyl-levodopa hydrochloride (Melevodopa) and the lipophilic Acyclovir. Various parameters of the 3DP coating process were purposefully modified using experimental design techniques in order to customize the selected APIs release profile, without affecting the core composition of the formulation. The percentage of the tablet surface coated, the number of coating layers as well as the coated sides of the tablet where the parameters which controlled the release profile for both APIs. Different dissolution profiles have been achieved by tuning these simple parameters, which revealed a non-Fickian release mechanism regardless of the API.

Exploring the oxidation and iron binding profile of a cyclodextrin encapsulated quercetin complex unveiled a controlled complex dissociation through a chemical stimulus.

BACKGROUND: Flavonoids possess a rich polypharmacological profile and their biological role is linked to their oxidation state protecting DNA from oxidative stress damage. However, their bioavailability is hampered due to their poor aqueous solubility. This can be surpassed through encapsulation to supramolecular carriers as cyclodextrin (CD). A quercetin- 2HP-ß-CD complex has been formerly reported by us. However, once the flavonoid is in its 2HP-ß-CD encapsulated state its oxidation potential, its decomplexation mechanism, its potential to protect DNA damage from oxidative stress remained elusive. To unveil this, an array of biophysical techniques was used. METHODS: The quercetin-2HP-ß-CD complex was evaluated through solubility and dissolution experiments, electrochemical and spectroelectrochemical studies (Cyclic Voltammetry), UV-Vis spectroscopy, HPLC-ESI-MS/MS and HPLC-DAD, fluorescence spectroscopy, NMR Spectroscopy, theoretical calculations (density functional theory (DFT)) and biological evaluation of the protection offered against H2O2-induced DNA damage. RESULTS: Encapsulation of quercetin inside the supramolecule's cavity enhanced its solubility and retained its oxidation profile. Although the protective ability of the quercetin-2HP-ß-CD complex against H2O2 was diminished, iron serves as a chemical stimulus to dissociate the complex and release quercetin. CONCLUSIONS: We found that in a quercetin-2HP-ß-CD inclusion complex quercetin retains its oxidation profile similarly to its native state, while iron can operate as a chemical stimulus to release quercetin from its host cavity. GENERAL SIGNIFICANCE: The oxidation profile of a natural product once it is encapsulated in a supramolecular carrier was unveiled as also it was discovered that decomplexation can be triggered by a chemical stimilus.

The application of Quality by Design framework in the pharmaceutical development of dry powder inhalers.

This review aims in discussing the application of the Quality by Design (QbD) approach on the development of the Dry Powders Inhalers (DPIs). It starts with a thorough presentation of the Quality's concept evolution within the pharmaceutical sector and how this slowly adopted set of quality guidelines is now a major scientific and regulatory requirement. DPIs represent a type of delivery system where the system's thinking approach integrating the device, the formulation and the patient represent a major challenge to be met. Within this context this review points out the critical gaps in this optimization exercise and proposes a series of remedies in overcoming the obstacles when the system's parts are viewed alone and not as a whole. Statistical thinking and the corresponding tools are the means for successfully carrying out this purpose. QbD is not just another guideline to simply comply with. It is the ultimate scope of any pharmaceutical development effort, which is to fully understand and then consistently meet the patient's needs during the entire lifecycle of the product. QbD is focusing on delivering quality value to the patients without compromises in product's safety and effectiveness profile.

Design of experiments (DoE) in pharmaceutical development.

At the beginning of the twentieth century, Sir Ronald Fisher introduced the concept of applying statistical analysis during the planning stages of research rather than at the end of experimentation. When statistical thinking is applied from the design phase, it enables to build quality into the product, by adopting Deming's profound knowledge approach, comprising system thinking, variation understanding, theory of knowledge, and psychology. The pharmaceutical industry was late in adopting these paradigms, compared to other sectors. It heavily focused on blockbuster drugs, while formulation development was mainly performed by One Factor At a Time (OFAT) studies, rather than implementing Quality by Design (QbD) and modern engineering-based manufacturing methodologies. Among various mathematical modeling approaches, Design of Experiments (DoE) is extensively used for the implementation of QbD in both research and industrial settings. In QbD, product and process understanding is the key enabler of assuring quality in the final product. Knowledge is achieved by establishing models correlating the inputs with the outputs of the process. The mathematical relationships of the Critical Process Parameters (CPPs) and Material Attributes (CMAs) with the Critical Quality Attributes (CQAs) define the design space. Consequently, process understanding is well assured and rationally leads to a final product meeting the Quality Target Product Profile (QTPP). This review illustrates the principles of quality theory through the work of major contributors, the evolution of the QbD approach and the statistical toolset for its implementation. As such, DoE is presented in detail since it represents the first choice for rational pharmaceutical development.

Development of a fast, lean and agile direct pelletization process using experimental design techniques.

A novel hot melt direct pelletization method was developed, characterized and optimized, using statistical thinking and experimental design tools. Mixtures of carnauba wax (CW) and HPMC K100M were spheronized using melted gelucire 50-13 as a binding material (BM). Experimentation was performed sequentially; a fractional factorial design was set up initially to screen the factors affecting the process, namely spray rate, quantity of BM, rotor speed, type of rotor disk, lubricant-glidant presence, additional spheronization time, powder feeding rate and quantity. From the eight factors assessed, three were further studied during process optimization (spray rate, quantity of BM and powder feeding rate), at different ratios of the solid mixture of CW and HPMC K100M. The study demonstrated that the novel hot melt process is fast, efficient, reproducible and predictable. Therefore, it can be adopted in a lean and agile manufacturing setting for the production of flexible pellet dosage forms with various release rates easily customized between immediate and modified delivery.

How Do European Pharmacy Students Rank Competences for Practice?

European students (n = 370), academics (n = 241) and community pharmacists (n = 258) ranked 13 clusters of 68 personal and patient care competences for pharmacy practice. The results show that ranking profiles for all three groups as a rule were similar. This was especially true of the comparison between students and community pharmacists concerning patient care competences suggesting that students have a good idea of their future profession. A comparison of first and fifth (final) year students shows more awareness of patient care competences in the final year students. Differences do exist, however, between students and community pharmacists. Students-like academics-ranked competences concerned with industrial pharmacy and the quality aspects of preparing drugs, as well as scientific fundamentals of pharmacy practice, well above the rankings of community pharmacists. There were no substantial differences amongst rankings of students from different countries although some countries have more "medicinal" courses than others. This is to our knowledge the first paper to look at how, within a healthcare sectoral profession such as pharmacy, the views on the relative importance of different competences for practice of those educating the future professionals and their students, are compared to the views of working professionals.

What is a Pharmacist: Opinions of Pharmacy Department Academics and Community Pharmacists on Competences Required for Pharmacy Practice.

This paper looks at the opinions of 241 European academics (who provide pharmacy education), and of 258 European community pharmacists (who apply it), on competences for pharmacy practice. A proposal for competences was generated by a panel of experts using Delphi methodology. Once finalized, the proposal was then submitted to a large, European-wide community of academics and practicing pharmacists in an additional Delphi round. Academics and community pharmacy practitioners recognized the importance of the notion of patient care competences, underlining the nature of the pharmacist as a specialist of medicines. The survey revealed certain discrepancies. Academics placed substantial emphasis on research, pharmaceutical technology, regulatory aspects of quality, etc., but these were ranked much lower by community pharmacists who concentrated more on patient care competences. In a sub-analysis of the data, we evaluated how perceptions may have changed since the 1980s and the introduction of the notions of competence and pharmaceutical care. This was done by splitting both groups into respondents < 40 and > 40 years old. Results for the subgroups were essentially statistically the same but with some different qualitative tendencies. The results are discussed in the light of the different conceptions of the professional identity of the pharmacist.

A Study on How Industrial Pharmacists Rank Competences for Pharmacy Practice: A Case for Industrial Pharmacy Specialization.

This paper looks at the way in which industrial pharmacists rank the fundamental competences for pharmacy practice. European industrial pharmacists (n = 135) ranked 68 competences for practice, arranged into 13 clusters of two types (personal and patient care). Results show that, compared to community pharmacists (n = 258), industrial pharmacists rank competences centering on research, development and production of drugs higher, and those centering on patient care lower. Competences centering on values, communication skills, etc. were ranked similarly by the two groups of pharmacists. These results are discussed in the light of the existence or not of an "industrial pharmacy" specialization.

Hospital and Community Pharmacists' Perceptions of Which Competences Are Important for Their Practice.

The objective of the PHAR-QA (Quality assurance in European pharmacy education and training) project was to investigate how competence-based learning could be applied to a healthcare, sectoral profession such as pharmacy. This is the first study on evaluation of competences from the pharmacists' perspective using an improved Delphi method with a large number of respondents from all over Europe. This paper looks at the way in which hospital pharmacists rank the fundamental competences for pharmacy practice. European hospital pharmacists (n = 152) ranked 68 competences for pharmacy practice of two types (personal and patient care), arranged into 13 clusters. Results were compared to those obtained from community pharmacists (n = 258). Generally, hospital and community pharmacists rank competences in a similar way. Nevertheless, differences can be detected. The higher focus of hospital pharmacists on knowledge of the different areas of science as well as on laboratory tests reflects the idea of a hospital pharmacy specialisation. The difference is also visible in the field of drug production. This is a necessary competence in hospitals with requests for drugs for rare diseases, as well as paediatric and oncologic drugs. Hospital pharmacists give entrepreneurship a lower score, but cost-effectiveness a higher one than community pharmacists. This reflects the reality of pharmacy practice where community pharmacists have to act as entrepreneurs, and hospital pharmacists are managers staying within drug budgets. The results are discussed in the light of a "hospital pharmacy" specialisation.

The Second Round of the PHAR-QA Survey of Competences for Pharmacy Practice.

This paper presents the results of the second European Delphi round on the ranking of competences for pharmacy practice and compares these data to those of the first round already published. A comparison of the numbers of respondents, distribution by age group, country of residence, etc., shows that whilst the student population of respondents changed from Round 1 to 2, the populations of the professional groups (community, hospital and industrial pharmacists, pharmacists in other occupations and academics) were more stable. Results are given for the consensus of ranking and the scores of ranking of 50 competences for pharmacy practice. This two-stage, large-scale Delphi process harmonized and validated the Quality Assurance in European Pharmacy Education and Training (PHAR-QA) framework and ensured the adoption by the pharmacy profession of a framework proposed by the academic pharmacy community. The process of evaluation and validation of ranking of competences by the pharmacy profession is now complete, and the PHAR-QA consortium will now put forward a definitive PHAR-QA framework of competences for pharmacy practice.

Spray-dried amikacin sulphate powder for inhalation in cystic fibrosis patients: The role of ethanol in particle formation.

A Central Composite Design (CCD) was applied in order to identify positive combinations of the production parameters of amikacin sulphate spray-dried powders for inhalation, with the intent to expand the experimental space defined in a previous half-fractional factorial design. Three factors, namely drying temperature, feed rate and ethanol proportion, have been selected out of the initial five. In addition, the levels of these factors were increased from two to three and their effect on amikacin respirability was evaluated. In particular, focus was given on the role of ethanol presence on the formation of the microparticles for inhalation. The overall outcome of the CCD was that amikacin respirability was not substantially improved, as the optimum region coincided with areas already explored with the fractional factorial design. However, expanding the design space towards smaller ethanol levels, including its complete absence, revealed the crucial role of this solvent on the morphology of the produced particles. Peclet number and drug solubility in the spraying solution helped to understand the formation mechanism of these amikacin sulphate spray-dried particles.