Co-administration of Intravenous Drugs: Rapidly Troubleshooting the Solid Form Composition of a Precipitate in a Multi-drug Mixture Using On-Site Raman Spectroscopy.

Intravenous drugs are often co-administrated in the same intravenous catheter line due to which compatibility issues, such as complex precipitation processes in the catheter line, may occur. A well-known example that led to several neonatal deaths is the precipitation due to co-administration of ceftriaxone- and calcium-containing solutions. The current study is exploring the applicability of Raman spectroscopy for testing intravenous drug compatibility in hospital settings. The precipitation of ceftriaxone calcium was used as a model system and explored in several multi-drug mixtures containing both structurally similar and clinically relevant drugs for co-infusion. Equal molar concentrations of solutions containing ceftriaxone and calcium chloride dihydrate were mixed with solutions of cefotaxime, ampicillin, paracetamol, and metoclopramide. The precipitate formed was collected as an "unknown" material, dried, and analyzed. Several solid-state analytical methods, including X-ray powder diffraction, Raman spectroscopy, and thermogravimetric analysis, were used to characterize the precipitate. Raman microscopy was used to investigate the identity of single sub-visual particles precipitated from a mixture of ceftriaxone, cefotaxime, and calcium chloride. X-ray powder diffraction suggested that the precipitate was partially crystalline; however, the identity of the solid form of the precipitate could not be confirmed with this standard method. Raman spectroscopy combined with multi-variate analyses (principal component analysis and soft independent modelling class analogy) enabled the correct detection and identification of the precipitate as ceftriaxone calcium. Raman microscopy enabled the identification of ceftriaxone calcium single particles of sub-visual size (around 25 µm), which is in the size range that may occlude capillaries. This study indicates that Raman spectroscopy is a promising approach for supporting clinical decisions and especially for compatibility assessments of drug infusions in hospital settings.

Effect of pH on the Surface Layer of Molecular Crystals at the Solid-Liquid Interface.

Dissolution of solid matter into aqueous solution is one of the most challenging physicochemical aspects related to drug development. While influenced by several parameters, the effect of pH remains the most important one to be fully understood. The dissolution process is essentially controlled by activity at the surface of the molecular crystals, which is difficult to characterize experimentally. To address this, a combination of in situ atomic force microscopy (AFM) with molecular dynamics (MD) simulation is reported. AFM allows for direct visualization of the crystal surface of basic and acidic model compounds (carvedilol and ibuprofen) in contact with an aqueous medium with varying pH. A dramatic increase in surface mobility in the solid-liquid interface could be observed experimentally as a function of pH. The in situ AFM approach opens up for a more detailed understanding of the behavior of particulate matter in solution with importance at different levels, ranging from engineering aspects related to crystallization, and biological considerations related to bioavailability of the final drug product.

Additive Manufacturing of Solid Products for Oral Drug Delivery Using Binder Jetting Three-Dimensional Printing.

Binder jetting (BJ) three-dimensional (3D) printing is becoming an established additive manufacturing technology for manufacturing of solid products for oral drug delivery. Similar to traditional solutions based on compaction of powder mixture, successful processing of BJ products requires control of bulk powder properties. In contrast to traditional compaction-based process, BJ 3D printing allows for flexible modifications on microstructure, material composition and dose in the printed pharmaceutical products. Currently, systematic strategies for selecting excipients and optimizing the printing process have not been fully established. To address this challenge, a summary of the published work and selected patent literature around BJ 3D printing to fabricate pharmaceutical solid products for oral administration purposes is presented. First, an overview of characteristics of printed products as a part of the product design and a description of the commonly used excipients and active pharmaceutical ingredients is given. The critical powder and ink properties, as well as physical geometries and inner structures of a final product, are discussed in term of the mechanisms that determine the formation of a printed solid product and finally the quality of this product. This review is also summarizing the technical features of printers, printheads, and the critical considerations for post-processing procedures. BJ 3D printing is one of the most promising additive manufacturing technologies for mass customization of pharmaceutical products.

Monitoring the Isothermal Dehydration of Crystalline Hydrates Using Low-Frequency Raman Spectroscopy.

Detection of the solid-state forms of pharmaceutical compounds is important from the drug performance point of view. Low-frequency Raman (LFR) spectroscopy has been demonstrated to be very sensitive in detecting the different solid-state forms of pharmaceutically relevant compounds. The potential of LFR spectroscopy to probe the in situ isothermal dehydration was studied using piroxicam monohydrate (PXM) and theophylline monohydrate (TPMH) as the model drugs. The dehydration of PXM and TPMH at four different temperatures (95, 100, 105, and 110 °C and 50, 60, 70, and 80 °C, respectively) was monitored in both the low- (20-300 cm-1) and mid-frequency (335-1800 cm-1) regions of the Raman spectra. Principal component analysis and multivariate curve resolution were applied for the analysis of the Raman data. Spectral differences observed in both regions highlighted the formation of specific anhydrous forms of piroxicam and theophylline from their respective monohydrates. The formation of the anhydrous forms was detected on different timescales (approx. 2 min) between the low and mid-frequency Raman regions. This finding highlights the differing nature of the vibrations being detected between these two spectral regions. Computational simulations performed were also in agreement with the experimental results, and allowed elucidating the origin of different spectral features.

Medication Tracking: Design and Fabrication of a Dry Powder Inhaler with Integrated Acoustic Element by 3D Printing.

PURPOSE: Asthma is a prevalent lung disorder that cause heavy burdens globally. Inhalation medicaments can relieve symptoms, improve lung function and, thus, the quality of life. However, it is well-documented that patients often do not get the prescribed dose out of an inhaler and the deposition of drug is suboptimal, due to incorrect handling of the device and wrong inhalation technique. This study aims to design and fabricate an acoustic dry powder inhaler (ADPI) for monitoring inhalation flow and related drug administration in order to evaluate whether the patient receives the complete dose out of the inhaler. METHODS: The devices were fabricated using 3D printing and the impact of the acoustic element geometry and printing resolution on the acoustic signal was investigated. Commercial Foradil (formoterol fumarate) capsules were used to validate the availability of the ADPI for medication dose tracking. The acoustic signal was analysed with Partial-Least-Squares (PLS) regression. RESULTS: Indicate that specific acoustic signals could be generated at different air flow rates using a passive acoustic element with specific design features. This acoustic signal could be correlated with the PLS model to the air flow rate. A more distinct sound spectra could be acquired at higher printing resolution. The sound spectra from the ADPI with no capsule, a full capsule and an empty capsule are different which could be used for medication tracking. CONCLUSIONS: This study shows that it is possible to evaluate the medication quality of inhaled medicaments by monitoring the acoustic signal generated during the inhalation process.

Temperature-Modulated Micromechanical Thermal Analysis with Microstring Resonators Detects Multiple Coherent Features of Small Molecule Glass Transition.

Micromechanical Thermal Analysis utilizes microstring resonators to analyze a minimum amount of sample to obtain both the thermal and mechanical responses of the sample during a heating ramp. We introduce a modulated setup by superimposing a sinusoidal heating on the linear heating and implementing a post-measurement data deconvolution process. This setup is utilized to take a closer look at the glass transition as an important fundamental feature of amorphous matter with relations to the processing and physical stability of small molecule drugs. With an additionally developed image and qualitative mode shape analysis, we are able to separate distinct features of the glass transition process and explain a previously observed two-fold change in resonance frequency. The results from this setup indicate the detection of initial relaxation to viscous flow onset as well as differences in mode responsivity and possible changes in the primary resonance mode of the string resonators. The modulated setup is helpful to distinguish these processes during the glass transition with varying responses in the frequency and quality factor domain and offers a more robust way to detect the glass transition compared to previously developed methods. Furthermore, practical and theoretical considerations are discussed when performing measurements on string resonators (and comparable emerging analytical techniques) for physicochemical characterization.

Continuous Manufacturing of a Polymer Stabilized Emulsion Monitored with Process Analytical Technology.

Moving from batch to continuous manufacturing (CM) requires implementation of process analytical technology (PAT), as it is crucial to monitor and control these processes. CM of semi-solids has been demonstrated but implementation of a broader range of PAT tools with in- or on-line process interfacing at the end of the CM line has not been demonstrated. The goal of this work was to continuously manufacture creams and to investigate whether in- and on-line measurement of viscosity, changes in the concentration of active pharmaceutical ingredient (API), and pH could be used to support optimization of a model cream product. Additionally, the torque of the mixers was assessed for determination of the physical properties of the cream. Two Raman probes with different probe optics were compared for characterization of the API concentration. The API concentration, amount of neutralizer, and mixing speed of the CM line were systematically varied. Both the PhAT probe with a larger sampling volume and immersion Raman probe with a smaller sampling volume could detect the step changes in the API concentration. The torque from the mixer was compared with the viscosity measurements, but the torque signal could not be correlated with the viscosity due to the dynamic nature of the polymer conformation and the time-dependency of this property. Adjustment of pH of the cream could be monitored with the current installation. The investigated PAT tools could be implemented into a continuous line and, further, be used to support the optimization of a model cream composition and related process parameters.

The Use of 3D Printed Molds to Cast Tablets with a Designed Disintegration Profile.

Development of new product design principles is crucial for obtaining pharmaceutical products with controlled functionality. Four different molds were designed using a computer-aided design (CAD) software and 3D printed with polylactic acid (PLA). A hydroxypropyl methylcellulose (HPMC) and polyethylene glycol (PEG)-based formulation containing indomethacin as the active pharmaceutical ingredient (API) was casted into the molds. Each mold produced a tablet that was designed to disintegrate into a defined number of sections (2, 4, and 6). This was achieved by incorporating break lines (regions that were significantly thinner than the remainder of the tablet) to control the disintegration process. Disintegration and drug release from these designed tablets was contrasted with a casted tablet without break lines. Disintegration studies confirmed that the casted tablets disintegrated according to their design. Drug-release studies meanwhile demonstrated that tablets with a greater number of sections released the API at a faster rate than those with fewer sections; for example, the 6-sectioned tablet released the API at twice the rate of the tablet without any break lines. It is expected that by using this concept, it would be possible to produce tablets with a designed disintegration profile, which could potentially allow the tailoring of the drug release.

Quantification of Inkjet-Printed Pharmaceuticals on Porous Substrates Using Raman Spectroscopy and Near-Infrared Spectroscopy.

The use of inkjet printing for pharmaceutical manufacturing is gaining interest for production of personalized dosage forms tailored to specific patients. As part of the manufacturing, it is imperative to ensure that the correct dose is printed. The aim of this study was to use inkjet printing for manufacturing of personalized dosage forms combined with the use of near-infrared (NIR) and Raman spectroscopy as complementary analytical techniques for active pharmaceutical ingredient (API) quantification of the inkjet-printed dosage forms. Three APIs, propranolol (0.5-4.1 mg), montelukast (2.1-12.1 mg), and haloperidol (0.6-4.1 mg) were inkjet printed in 1 cm2 areas on a porous substrate. The printed doses were non-destructively analyzed by transmission NIR and Raman spectroscopy (both transmission and backscatter). X-ray computed microtomography (µ-CT) analysis was undertaken for porosity measurements of the substrate. The API content was confirmed using high-performance liquid chromatography (HPLC), and the content in the dosage forms was modeled from the NIR and Raman spectra using partial least squares regression (PLS). HPLC analysis revealed a linear correlation of the number of layers printed to the API content. The resulting PLS models for both NIR and Raman had R2 values between 0.95 and 0.99. The best predictive model was obtained using NIR, followed by Raman spectroscopy. µ-CT revealed the substrate to be highly porous and optimal for inkjet printing. In conclusion, NIR and Raman spectroscopic techniques could be used complementary as fast API quantification tools for inkjet-printed medicines.

Correction to: Quantification of Inkjet-Printed Pharmaceuticals on Porous Substrates Using Raman Spectroscopy and Near-Infrared Spectroscopy.

Mohammed Al-Sharabi's affiliation was incorrect at the time of publishing. The updated affiliation appears below.

Ultrasensitive Microstring Resonators for Solid State Thermomechanical Analysis of Small and Large Molecules.

Thermal analysis plays an important role in both industrial and fundamental research and is widely used to study thermal characteristics of a variety of materials. However, despite considerable effort using different techniques, research struggles to resolve the physicochemical nature of many thermal transitions such as amorphous relaxations or structural changes in proteins. To overcome the limitations in sensitivity of conventional techniques and to gain new insight into the thermal and mechanical properties of small- and large-molecule samples, we have developed an instrumental analysis technique using resonating low-stress silicon nitride microstrings. With a simple sample deposition method and postprocess data analysis, we are able to perform rapid thermal analysis of direct instrumental triplicate samples with only pico- to nanograms of material. Utilizing this method, we present the first measurement of amorphous alpha and beta relaxation, as well as liquid crystalline transitions and decomposition of small-molecule samples deposited onto a microstring resonator. Furthermore, sensitive measurements of the glass transition of polymers and yet unresolved thermal responses of proteins below their apparent denaturation temperature, which seem to include the true solid state glass transition of pure protein, are reported. Where applicable, thermal events detected with the setup were in good agreement with conventional techniques such as differential scanning calorimetry and dynamic mechanical analysis. The sensitive detection of even subtle thermal transitions highlights further possibilities and applications of resonating microstrings in instrumental physicochemical analysis.

Using 3D Printing for Rapid Prototyping of Characterization Tools for Investigating Powder Blend Behavior.

There is an increasing need to provide more detailed insight into the behavior of particulate systems. The current powder characterization tools are developed empirically and in many cases, modification of existing equipment is difficult. More flexible tools are needed to provide understanding of complex powder behavior, such as mixing process and segregation phenomenon. An approach based on the fast prototyping of new powder handling geometries and interfacing solutions for process analytical tools is reported. This study utilized 3D printing for rapid prototyping of customized geometries; overall goal was to assess mixing process of powder blends at small-scale with a combination of spectroscopic and mechanical monitoring. As part of the segregation evaluation studies, the flowability of three different paracetamol/filler-blends at different ratios was investigated, inter alia to define the percolation thresholds. Blends with a paracetamol wt% above the percolation threshold were subsequently investigated in relation to their segregation behavior. Rapid prototyping using 3D printing allowed designing two funnels with tailored flow behavior (funnel flow) of model formulations, which could be monitored with an in-line near-infrared (NIR) spectrometer. Calculating the root mean square (RMS) of the scores of the two first principal components of the NIR spectra visualized spectral variation as a function of process time. In a same setup, mechanical properties (basic flow energy) of the powder blend were monitored during blending. Rapid prototyping allowed for fast modification of powder testing geometries and easy interfacing with process analytical tools, opening new possibilities for more detailed powder characterization.

Visualization and Non-Destructive Quantification of Inkjet-Printed Pharmaceuticals on Different Substrates Using Raman Spectroscopy and Raman Chemical Imaging.

PURPOSE: The purpose of this study was to investigate the applicability of Raman spectroscopy for visualization and quantification of inkjet-printed pharmaceuticals. METHODS: Haloperidol was used as a model active pharmaceutical ingredient (API), and a printable ink base containing lactic acid and ethanol was developed. Inkjet printing technology was used to apply haloperidol ink onto three different substrates. Custom-made inorganic compacts and dry foam, as well as marketed paracetamol tablets were used as the substrates. RESULTS: Therapeutic personalized doses were printed by using one to ten printing rounds on the substrates. The haloperidol content in the finished dosage forms were determined by high-performance liquid chromatography (HPLC). The distribution of the haloperidol on the dosage forms were visualized using Raman chemical imaging combined with principal components analysis (PCA). Raman spectroscopy combined with modeling by partial least squares (PLS) regression was used for establishment of a quantitative model of the haloperidol content in the printed dosage forms. A good prediction of the haloperidol content was achieved for the inorganic compacts, while a slightly poorer prediction was observed for the paracetamol tablets. It was not possible to quantify haloperidol on the dry foam due to the low and varying density of the substrate. CONCLUSIONS: Raman spectroscopy is a useful tool for visualization and quality control of inkjet printed personalized medicine.

Melt Extrusion of High-Dose Co-Amorphous Drug-Drug Combinations : Theme: Formulation and Manufacturing of Solid Dosage Forms Guest Editors: Tony Zhou and Tonglei Li.

PURPOSE: Many future drug products will be based on innovative manufacturing solutions, which will increase the need for a thorough understanding of the interplay between drug material properties and processability. In this study, hot melt extrusion of a drug-drug mixture with minimal amount of polymeric excipient was investigated. METHODS: Using indomethacin-cimetidine as a model drug-drug system, processability of physical mixtures with and without 5% (w/w) of polyethylene oxide (PEO) were studied using Differential Scanning Calorimetry (DSC) and Small Amplitude Oscillatory Shear (SAOS) rheometry. Extrudates containing a co-amorphous glass solution were produced and the solid-state composition of these was studied with DSC. RESULTS: Rheological analysis indicated that the studied systems display viscosities higher than expected for small molecule melts and addition of PEO decreased the viscosity of the melt. Extrudates of indomethacin-cimetidine alone displayed amorphous-amorphous phase separation after 4 weeks of storage, whereas no phase separation was observed during the 16 week storage of the indomethacin-cimetidine extrudates containing 5% (w/w) PEO. CONCLUSIONS: Melt extrusion of co-amorphous extrudates with low amounts of polymer was found to be a feasible manufacturing technique. Addition of 5% (w/w) polymer reduced melt viscosity and prevented phase separation.

Analysis of 3D Prints by X-ray Computed Microtomography and Terahertz Pulsed Imaging.

PURPOSE: A 3D printer was used to realise compartmental dosage forms containing multiple active pharmaceutical ingredient (API) formulations. This work demonstrates the microstructural characterisation of 3D printed solid dosage forms using X-ray computed microtomography (XµCT) and terahertz pulsed imaging (TPI). METHODS: Printing was performed with either polyvinyl alcohol (PVA) or polylactic acid (PLA). The structures were examined by XµCT and TPI. Liquid self-nanoemulsifying drug delivery system (SNEDDS) formulations containing saquinavir and halofantrine were incorporated into the 3D printed compartmentalised structures and in vitro drug release determined. RESULTS: A clear difference in terms of pore structure between PVA and PLA prints was observed by extracting the porosity (5.5% for PVA and 0.2% for PLA prints), pore length and pore volume from the XµCT data. The print resolution and accuracy was characterised by XµCT and TPI on the basis of the computer-aided design (CAD) models of the dosage form (compartmentalised PVA structures were 7.5 ± 0.75% larger than designed; n = 3). CONCLUSIONS: The 3D printer can reproduce specific structures very accurately, whereas the 3D prints can deviate from the designed model. The microstructural information extracted by XµCT and TPI will assist to gain a better understanding about the performance of 3D printed dosage forms.

Electrospinnability of Poly Lactic-co-glycolic Acid (PLGA): the Role of Solvent Type and Solvent Composition.

PURPOSE: In this study, the electrospinnability of poly(lactic-co-glycolic acid) (PLGA) solutions was investigated, with a focus on understanding the influence of molecular weight of PLGA, solvent type and solvent composition on the physical properties of electrospun nanofibers. METHOD: Various solvents were tested to dissolve two PLGA grades (50 KDa-RG755, 100 KDa-RG750). The viscoelasticity, surface tension, and evaporation rate of the PLGA solutions were characterized prior to the electrospinning process. The resulting electrospun nanofibers were characterized with respect to the morphology and mechanical properties. RESULTS: Two pairs of solvent mixtures, i.e. dimethylformamide (DMF)-tetrahydrofuran (THF) and DMF-chloroform (CHL), were identified to provide a stable cone-jet. Within the polymer concentration range studied (10-30%, w/v), RG750 solutions could be electrospun into uniform fibers at 30% (w/v) or at 20% (w/v) when modifying the solvent composition. In comparison to DMF-THF solution, fibers had larger diameter, higher stiffness and tensile strength when electrospun from DMF-CHL solution. CONCLUSION: The high molecular weight polymer could ensure sufficient intermolecular interaction to generate uniform fibers. The solvent could influence the morphology and mechanical properties of the electrospun fibers by altering the properties of PLGA solution, and drying rate of fibers in the electrospinning process.

Colorimetry as Quality Control Tool for Individual Inkjet-Printed Pediatric Formulations.

Printing technologies were recently introduced to the pharmaceutical field for manufacturing of drug delivery systems. Printing allows on demand manufacturing of flexible pharmaceutical doses in a personalized manner, which is critical for a successful and safe treatment of patient populations with specific needs, such as children and the elderly, and patients facing multimorbidity. Printing of pharmaceuticals as technique generates new demands on the quality control procedures. For example, rapid quality control is needed as the printing can be done on demand and at the point of care. This study evaluated the potential use of a handheld colorimetry device for quality control of printed doses of vitamin Bs on edible rice and sugar substrates. The structural features of the substrates with and without ink were also compared. A multicomponent ink formulation with vitamin B1, B2, B3, and B6 was developed. Doses (4 cm2) were prepared by applying 1-10 layers of yellow ink onto the white substrates using thermal inkjet technology. The colorimetric method was seen to be viable in detecting doses up to the 5th and 6th printed layers until color saturation of the yellow color parameter (b*) was observed on the substrates. Liquid chromatography mass spectrometry was used as a reference method for the colorimetry measurements plotted against the number of printed layers. It was concluded that colorimetry could be used as a quality control tool for detection of different doses. However, optimization of the color addition needs to be done to avoid color saturation within the planned dose interval.

Properties of the Sodium Naproxen-Lactose-Tetrahydrate Co-Crystal upon Processing and Storage.

Co-crystals and co-amorphous systems are two strategies to improve the physical properties of an active pharmaceutical ingredient and, thus, have recently gained considerable interest both in academia and the pharmaceutical industry. In this study, the behavior of the recently identified sodium naproxen-lactose-tetrahydrate co-crystal and the co-amorphous mixture of sodium, naproxen, and lactose was investigated. The structure of the co-crystal is described using single-crystal X-ray diffraction. The structural analysis revealed a monoclinic lattice, space group P21, with the asymmetric unit containing one molecule of lactose, one of naproxen, sodium, and four water molecules. Upon heating, it was observed that the co-crystal transforms into a co-amorphous system due to the loss of its crystalline bound water. Dehydration and co-amorphization were studied using synchrotron X-ray radiation and thermogravimetric analysis (TGA). Subsequently, different processing techniques (ball milling, spray drying, and dehydration) were used to prepare the co-amorphous mixture of sodium, naproxen, and lactose. X-ray powder diffraction (XRPD) revealed the amorphous nature of the mixtures after preparation. Differential scanning calorimetry (DSC) analysis showed that the blends were single-phase co-amorphous systems as indicated by a single glass transition temperature. The samples were subsequently tested for physical stability under dry (silica gel at 25 and 40 °C) and humid conditions (25 °C/75% RH). The co-amorphous samples stored at 25 °C/75% RH quickly recrystallized into the co-crystalline state. On the other hand, the samples stored under dry conditions remained physically stable after five months of storage, except the ball milled sample stored at 40 °C which showed signs of recrystallization. Under these dry conditions, however, the ball-milled co-amorphous blend crystallized into the individual crystalline components.

Rapid Assessment of Tablet Film Coating Quality by Multispectral UV Imaging.

Chemical imaging techniques are beneficial for control of tablet coating layer quality as they provide spectral and spatial information and allow characterization of various types of coating defects. The purpose of this study was to assess the applicability of multispectral UV imaging for assessment of the coating layer quality of tablets. UV images were used to detect, characterize, and localize coating layer defects such as chipped parts, inhomogeneities, and cracks, as well as to evaluate the coating surface texture. Acetylsalicylic acid tablets were prepared on a rotary tablet press and coated with a polyvinyl alcohol-polyethylene glycol graft copolymer using a pan coater. It was demonstrated that the coating intactness can be assessed accurately and fast by UV imaging. The different types of coating defects could be differentiated and localized based on multivariate image analysis and Soft Independent Modeling by Class Analogy applied to the UV images. Tablets with inhomogeneous texture of the coating could be identified and distinguished from those with a homogeneous surface texture. Consequently, UV imaging was shown to be well-suited for monitoring of the tablet coating layer quality. UV imaging is a promising technique for fast quality control of the tablet coating because of the high data acquisition speed and its nondestructive analytical nature.

Raman mapping of mannitol/lysozyme particles produced via spray drying and single droplet drying.

PURPOSE: This study aimed to investigate the effect of a model protein on the solid state of a commonly used bulk agent in spray-dried formulations. METHODS: A series of lysozyme/mannitol formulations were spray-dried using a lab-scale spray dryer. Further, the surface temperature of drying droplet/particles was monitored using the DRYING KINETICS ANALYZER™ (DKA) with controllable drying conditions mimicking the spray-drying process to estimate the drying kinetics of the lysozyme/mannitol formulations. The mannitol polymorphism and the spatial distribution of lysozyme in the particles were examined using X-ray powder diffractometry (XRPD) and Raman microscopy. Partial Least Squares Discriminant Analysis was used for analyzing the Raman microscopy data. RESULTS: XRPD results indicated that a mixture of ß-mannitol and α-mannitol was produced in the spray-drying process which was supported by the Raman analysis, whereas Raman analysis indicated that a mixture of α-mannitol and δ-mannitol was detected in the single particles from DKA. In addition Raman mapping indicated that the presence of lysozyme seemed to favor the appearance of α-mannitol in the particles from DKA evidenced by close proximity of lysozyme and mannitol in the particles. CONCLUSIONS: It suggested that the presence of lysozyme tend to induce metastable solid state forms upon the drying process.