Real-Time Quantitative Evaluation of a Drug during Liposome Preparation Using a Probe-Type Raman Spectrometer.

During the manufacturing process of liposome formulations, it is considered difficult to evaluate their physicochemical properties and biological profiles due to the complexity of their structure and manufacturing process. Conventional quality evaluation is labor-intensive and time-consuming; therefore, there was a need to introduce a method that could perform in-line, real-time evaluation during the manufacturing process. In this study, Raman spectroscopy was used to monitor in real time the encapsulation of drugs into liposomes and the drug release, which are particularly important quality evaluation items. Furthermore, Raman spectroscopy combined with partial least-squares (PLS) analysis was used for quantitative drug evaluation to assess consistency with results from UV-visible spectrophotometry (UV), a common quantification method. The prepared various ciprofloxacin (CPFX) liposomes were placed in cellulose tubes, and a probe-type Raman spectrophotometer was used to monitor drug encapsulation, the removal of unencapsulated drug, and drug release characteristics in real time using a dialysis method. In the Raman spectra of the liposomes prepared by remote loading, the intensities of the CPFX-derived peaks increased upon drug encapsulation and showed a slight decrease upon removal of the unencapsulated drug. Furthermore, the peak intensity decreased more gradually during the drug release. In all Raman monitoring experiments, the discrepancy between quantified values of CPFX concentration in liposomes, as measured by Raman spectroscopy combined with partial least-squares (PLS) analysis, and those obtained through ultraviolet (UV) spectrophotometry was within 6.7%. The results revealed that the quantitative evaluation of drugs using a combination of Raman spectroscopy and PLS analysis was as accurate as the evaluation using UV spectrophotometry, which was used for comparison. These results indicate the promising potential of Raman spectroscopy as an innovative method for the quality evaluation of liposomal formulations.

Quabodepistat (OPC-167832), a Novel Antituberculosis Drug Candidate: Enhancing Oral Bioavailability via Cocrystallization and Mechanistic Analysis of Bioavailability in Two Cocrystals.

Quabodepistat (code name OPC-167832) is a novel antituberculosis drug candidate. This study aimed to discover cocrystals that improve oral bioavailability and to elucidate the mechanistic differences underlying the bioavailability of different cocrystals. Screening yielded two cocrystals containing 2,5-dihydroxybenzoic acid (2,5DHBA) or 2-hydroxybenzoic acid (2HBA). In bioavailability studies in beagle dogs, both cocrystals exhibited better bioavailability than the free form; however, the extent of bioavailability of cocrystals with 2HBA (quabodepistat-2HBA) was 1.4-fold greater than that of cocrystals with 2,5DHBA (quabodepistat-2,5DHBA). Dissolution studies at pH 1.2 yielded similar profiles for both cocrystals, although the percent dissolution differed: quabodepistat-2HBA dissolved more slowly than quabodepistat-2,5DHBA. The poor solubility of quabodepistat-2HBA is likely the primary factor limiting dissolution at pH 1.2. To identify a dissolution method that maintains the bioavailability in beagle dogs, we performed pH-shift dissolution studies that mimic the dynamic pH change from the stomach to the small intestine. Quabodepistat-2HBA demonstrated supersaturation after the pH was increased to 6.8, while quabodepistat-2,5DHBA did not demonstrate supersaturation. This result was consistent with the results of bioavailability studies in beagle dogs. We conclude that a larger quantity of orally administered quabodepistat-2HBA remained in its cocrystal form while being transferred to the small intestine compared with quabodepistat-2,5DHBA.

Effects of wet granulation process variables on the quantitative assay model of transmission Raman spectroscopy for pharmaceutical tablets.

Transmission Raman spectroscopy (TRS) is a process analytical technology tool for nondestructive analysis of drug content in tablets. Although wet granulation is the most used tablet manufacturing method, most TRS studies have focused on tablets manufactured via direct compression. The effects of upstream process parameter variations, such as granulation, on the prediction performance of TRS quantitative models are unknown. We evaluated the effects of process parameter variations during granulation on the prediction performance of the TRS quantitative model. Tablets with a drug concentration of 1%w/w were used. We developed PLS calibration models for the drug concentration range of 70-130% label claims. Subsequently, we predicted the drug content of the tablets with different granulation parameters. The results of our study demonstrate that the variation in the predicted recovery due to the variation in granulation parameters was practically acceptable. The calibration model showed a good prediction performance for tablets manufactured at different granulation scales and thicknesses. Therefore, we conclude that TRS quantitative models are robust to variations in upstream processes, such as granulation and downstream variations in tableting parameters. These results suggest that TRS is a versatile non-destructive quantitative analysis method that can be applied in tablet manufacturing.

Pharmaceutical Evaluation of Levofloxacin Orally Disintegrating Tablet Formulation Using Low Frequency Raman Spectroscopy.

We evaluated the pharmaceutical properties of levofloxacin (LV) in the form of an orally disintegrating tablet (LVODT) to find a new usefulness of low frequency (LF) Raman spectroscopy. LVODT contained dispersed granules with diameters in the order of several hundred micrometers, which were composed of the active pharmaceutical ingredient (API), as confirmed by infrared (IR) microspectroscopy. On the contrary, the API and inactive pharmaceutical ingredients (non-APIs) were homogeneously distributed in LV tablet (LVT) formulations. Microscopic IR spectroscopy and thermal analyses showed that LVODT and LVT contained the API in different crystalline forms or environment around the API each other. Furthermore, powder X-ray diffraction showed that LVT contained a hemihydrate of the API, while LVODT showed a partial transition to the monohydrate form. This result was confirmed by microscopic LF Raman spectroscopy. Moreover, this method confirmed the presence of thin layers coating the outer edges of the granules that contained the API. Spectra obtained from these thin layers indicated the presence of titanium dioxide, suggesting that the layers coexisted with a polymer that masks the bitterness of API. The microscopic LF Raman spectroscopy results in this study indicated new applications of this method in pharmaceutical science.

Evaluation of the Effect of Disintegrant Distribution on the Dissolution Behavior of Pharmaceutical Tablets Using Raman Chemical Imaging.

In pharmaceutics, substandard drug manufacturing can sometimes occur. Usually, end-product release tests are conducted to detect defective products, but in many cases, they are not able to identify the root causes of quality defects. In recent years, chemical imaging techniques have been widely used to study quality defects by visualizing the distribution of components in solid dosage forms. However, in most studies, the causes are predicted from images of ingredients, and the impact of each factor is unclear. In this study, we prepared model tablets and intentionally changed only the distribution of disintegrants, and visualized this distribution using the Raman chemical imaging technique to evaluate the effect on the dissolution behavior of the tablets. We found that tablet disintegration occurs completely when the amount of disintegrant is sufficient to disintegrate the tablet and is distributed throughout the tablet, even if the distribution is not uniform. In contrast, if there was a large area where the disintegrant was not present, the tablet did not disintegrate sufficiently. This suggests that it is more important that a sufficient amount of disintegrant is present throughout the tablet rather than the degree of deviation of disintegrant distribution.

Quality Evaluation of Humidified Magnesium Oxide Tablet Formulations with Respect to Disintegration Time Prolongation.

In the present study, we conducted a detailed evaluation of the effects of humidification on the quality of five types of commercial magnesium oxide (MgO) tablet formulations. When near-IR spectroscopy was performed, a peak derived from the first overtone of the stretching vibration of the hydroxyl group was observed at approximately 7200 cm-1 in a humidified MgO tablet formulation. To visually evaluate the effect of this humidification, a mapping image was created using microscopic IR spectroscopy. In the IR spectrum, a peak derived from the stretching vibration of the hydroxyl group appears at approximately 3700 cm-1, so we created a mapping image using the absorbance ratio of 3700 and 3400 cm-1 as an index. In the mapping image of humidified MgO tablet formulations, many areas had a higher absorbance ratio than the dried tablet formulations. From these results, it is qualitatively confirmed that the MgO was changed to magnesium hydroxide (Mg(OH)2) by humidification. Although these results were observed in the four types of MgO tablet formulations, only one type of tablet formulation was less affected by humidification. In addition, although most tablet formulations tended to prolong disintegration time due to humidification, there was almost no effect of humidification on the disintegration time in one type of tablet formulation, which had little change in the above evaluation. Thus, in most commercial MgO tablet formulations, humidification prolongs the disintegration time, and Mg(OH)2 significantly contributes to this factor.

Internuclear distance measurements between 1H and 14N in multi-component rigid solids at fast MAS.

1H-14N internuclear distances are readily and accurately measured using the symmetry-based phase-modulated resonance-echo saturation-pulse double-resonance (PM-S-RESPDOR) method in rigid solids. The fraction curve, (S0 - S')/S0, is represented by a single variable of a 1H-14N heteronuclear dipolar coupling, where S0 and S' are the PM-S-RESPDOR signal intensity with and without 14N PM saturation pulse, respectively. Analytical equation of the fraction curve easily provides 1H-14N couplings. This treatment is only applicable when NH proton resonance is well separated from the other proton peaks. With the limited 1H resolution even at fast MAS > 60 kHz, unfortunately, this condition is not necessarily satisfied especially in multi-component systems which often appear in pharmaceutical applications. To overcome this problem, T-HMQC filtering is applied to suppress the 1H signals other than NH proton prior to the PM-S-RESPDOR experiments. The method is well demonstrated on two components acetaminophen-oxalic acid (APAP-OXA) systems. Further analysis of orientation dependence of T-HMQC and PM-S-RESPDOR shows that the analytical equation can be safely applied in the analysis of T-HMQC filtered PM-S-RESPDOR experiments.

Quantitative Monitoring of Cocrystal Polymorphisms in Model Tablets Using Transmission Low-Frequency Raman Spectroscopy.

Cocrystallization is a technique for improving the physical properties of active pharmaceutical ingredients. However, cocrystals can transform into more stable polymorphs as well as dissociate to original materials. Therefore, an analytical technique is required to determine the polymorphic transformation quickly and accurately in tablets. The purpose of this study is to develop a method to monitor cocrystal polymorphs in model tablets using transmission low-frequency Raman spectroscopy. The tablets, consisting of only metastable polymorphs of caffeine-glutaric acid cocrystals, were stored under various relative humidity levels. The composition of the cocrystal polymorphs were calculated from a calibration curve relating the actual composition to the predicted values calculated by partial least squares regression processing of low-frequency Raman spectra. The metastable form gradually converted to a stable form, and polymorphic phase transformation occurred with increasing relative humidity. Ninety-six percent of the metastable form converted into a stable form stored at 25 °C after 3 h at 95% RH. In conclusion, transmission low-frequency Raman spectroscopy can be used to quantitatively monitor cocrystal polymorphs. This technique is one of the candidate techniques to quantifiably evaluate the physico-chemical stability of cocrystal polymorphs in tablets.

Theoretical evaluation of supersaturation of amorphous solid dispersion formulations with different drug/polymer combinations using mathematical modeling.

Amorphous solid dispersion (ASD) is a preparation widely used for improving the solubility and low oral absorbability of poorly water-soluble drugs, but the quantitative analysis of its dissolution profiles and its supersaturation status remains an important issue. We previously reported a new mathematical model for analyzing the dissolution characteristics of ASD preparations that enabled evaluation of theoretical solubility of ASDs and crystal precipitation rate constants of ASD preparations. In this study, to analyze the relationship between the mathematical parameters of the model and the dissolution behavior in detail, we simulated the dissolution behaviors upon changing parameters. We quantitatively evaluated the supersaturation of ASD preparations composed of various combinations of two drugs (ibuprofen or indomethacin) and three polymers (polyvinylpyrrolidone (PVP), copovidone or hydroxypropylmethylcellulose (HPMC)). Based on parameter comparison, the difference in the peak of drug concentration between IB/PVP and IB/HPMC ASDs was found to be derived from precipitation rate constant, not the theoretical solubility. In addition, although IMC/PVP ASD had higher solubility than IMC/HPMC ASDs, HPMC could suppress crystal precipitation and maintain supersaturation at higher concentrations than IMC/PVP ASD by comparing parameters derived from model fitting. Thus, our results show that the use of mathematical parameters can illuminate theoretical mechanical information regarding dissolution behaviors of various ASDs and permit a visualization of the character of the dissolution process.

Amorphous characterization of pharmaceutical drug substances enabled by the elastic modulus mapping of atomic force microscope.

The states of amorphous drug and/or newly generated crystalline drug on the surface of amorphous drug samples must be carefully characterized to validate the quality of pharmaceutical amorphous drugs. In this study, we investigated whether individual mechanical properties of amorphous and crystalline drugs could be discerned by an atomic force microscope (AFM) with a mapping. Among mechanical properties, the amorphous and crystal drugs were quantitatively distinguished by elastic modulus using PeakForceTM quantitative nanomechanical mapping. The elastic modulus of the crystals exceeded 10 GPa-significantly higher than that of the amorphous, which was ≤5 GPa in all five model drugs; consequently, ≤200 nm scale crystals were detected on amorphous surfaces. Furthermore, the elastic modulus reflected the difference in the amorphous states between the molten and the solvent-evaporated preparations in the microscopic area, thereby demonstrating the ability of AFM to characterize amorphous states. Taken together, AFM measurements using elastic modulus can be an effective analytical tool to provide microscale mapping and characterization of amorphous surfaces, leading to enhanced amorphous drug development.

[Evaluation of the Pharmaceutical Properties of Clobetasol Propionate Ointments and Base Stability of the Mixture with Heparinoid Oil Based Creams].

Clobetasol propionate ointment (CLPO) formulations have been classified as members of the "strongest" steroidal efficacy group, with eight of these formulations currently marketed in Japan. Evaluations of pharmaceutical properties of each formulation revealed three classification types: droplet dispersion type containing propylene glycol (PG) and surfactant, type with surfactant but not PG, and other types. These rheological properties were diverse, with no correlation found between viscosity and ointment type. However, when CLPO and six types of heparinoid oil-based cream (HPOC) formulation mixtures were stored at 37℃, a liquid layer was observed starting at 24 h for one CLPO formulation in which polyoxyethylene hydrogenated castor oil 40 was used as a surfactant out of the four droplet-dispersion type ointments and two low-viscosity HPOC formulations. In contrast, one other type of CLPO formulation that contained a surfactant with polysorbate 80, but not PG, exhibited a liquid layer for all of HPOC formulations. This suggests that CLPO formulations that contain a surfactant with a high hydrophilic-lipophilic balance value are likely to generate a liquid layer for mixtures containing HPOC formulation. The present results demonstrate that not only the pharmaceutical properties of the eight CLPO formulations differ from one another, but also that the stabilities of HPOC formulation mixtures are significantly different. Therefore, pharmacists need to focus on inactive as well as active pharmaceutical ingredients to select formulations that patients will want to use, in addition to successfully treating their pathological conditions.

Non-destructive quantitative analysis of pharmaceutical ointment by transmission Raman spectroscopy.

Transmission Raman spectroscopy was used to develop a non-destructive quantitative analytical model for the assay of a crystal dispersion-type ointment containing acyclovir as a model drug with a concentration of 3% w/w. The obtained Raman spectra were pre-processed by applying multiplicative scatter correction, standard normal variate, and first or second derivative by the Savitzky-Golay method to optimize the partial least squares (PLS) regression model. The optimized PLS model showed good prediction performance for 85%, 100%, and 115% label claims, with average recovery values of 100.7%, 99.3%, and 99.8%, respectively. Although the material properties and manufacturing method of acyclovir and white petrolatum were expected to be different from those of the calibration set, the mean recovery value of the commercial product was 104.2%. These results indicate that transmission Raman spectroscopy is a useful process analytical technology tool for product development and quality control of a crystal dispersion-type ointment with low drug concentration.

Four Novel Pharmaceutical Cocrystals of Oxyresveratrol, Including a 2 : 3 Cocrystal with Betaine.

Cocrystal engineering can alter the physicochemical properties of a drug and generate a superior drug candidate for formulation design. Oxyresveratrol (ORV) exhibits a poor solubility in aqueous environments, thereby resulting in a poor bioavailability. Extensive cocrystal screening of ORV with 67 cocrystal formers (coformers) bearing various functional groups was therefore conducted using grinding, liquid-assisted grinding, solvent evaporation, and slurry methods. Six cocrystals (ORV with betaine (BTN), L-proline (PRL), isonicotinamide, nicotinamide, urea, and ethyl maltol) were found, including four novel cocrystals. Powder X-ray diffraction, low frequency Raman spectroscopy, and thermal analysis revealed unique crystal forms in all obtained samples. Conventional Raman and infrared data differentiated the cocrystals by the presence or absence of a hydrogen bond interacting with the aromatic ring of ORV. The crystal structures were then elucidated by single-crystal X-ray diffraction. Two new cocrystals consisting of ORV : BTN (2 : 3) and ORV : PRL : H2O (1 : 2 : 1) were identified, and their crystal structures were solved. We report novel cocrystalline solids of ORV with improved aqueous solubilities and the unique cage-like crystal structures.

Monitoring of Cocrystal Dissociation during the Wet Granulation Process in the Presence of Disintegrants by Using Low-Frequency Raman Spectroscopy.

The aim of this study was to evaluate the effect of three coformers and five disintegrants in the granulation formulation on the dissociation of cocrystal during the granulation process by monitoring wet granulation with probe-type low-frequency Raman (LF-Raman) spectroscopy. As model cocrystals, paracetamol (APAP)-oxalic acid (OXA), APAP-maleic acid (MLA), and APAP-trimethylglycine (TMG) were used. The monitoring of the granulation recipe containing cocrystals during wet granulation was performed over time with high-performance LF-Raman spectrometry and the dissociation rate was calculated from the results of multivariate analysis of LF-Raman spectra. The dissociation rate decreased in the order of APAP-TMG, APAP-OXA, and APAP-MLA, showing the same order as observed in Powder X-ray diffraction measurements. Furthermore, to compare the effect of disintegrants on the dissociation rate of APAP-OXA, LF-Raman monitoring was performed for the granulation recipes containing five typical disintegrants (two low-substitution hydroxypropyl cellulose (HPC), cornstarch (CSW), carmellose sodium (CMC), and crospovidone (CRP)). The dissociation rate of APAP-OXA decreased in the order of CSW, HPCs, CMC, and CRP. This difference in the dissociation rate of APAP-OXA was thought to be due to the disintegration mechanism of the disintegrants and the water absorption ratio, which was expected to affect the water behavior on the disintegrant surface during wet granulation. These results suggested that probe-type LF-Raman spectroscopy is useful to monitor the dissociation behavior of cocrystals during wet granulation and can compare the relative stability of cocrystal during wet granulation between different formulations.

Pharmacokinetics of CuGTSM, a Novel Drug Candidate, in a Mouse Model of Menkes Disease.

PURPOSE: Menkes disease is a rare hereditary disease in which systemic deficiency of copper due to mutation of the ATP7A gene causes severe neurodegenerative disorders. The present parenteral drugs have limited efficacy, so there is a need for an efficacious drug that can be administered orally. This study focused on glyoxal-bis (N(4)-methylthiosemicarbazonato)-copper(II (CuGTSM), which has shown efficacy in macular mice, a murine model of Menkes disease, and examined its pharmacokinetics. In addition, nanosized CuGTSM (nCuGTSM) was prepared, and the effects of nanosizing on CuGTSM pharmacokinetics were investigated. METHODS: CuGTSM or nCuGTSM (10 mg/kg) was administered orally to male macular mice or C3H/HeNCrl mice (control), and plasma was obtained by serial blood sampling. Plasma concentrations of CuGTSM and GTSM were measured by LC-MS/MS and pharmacokinetic parameters were calculated. RESULTS: When CuGTSM was administered orally, CuGTSM and GTSM were both detected in the plasma of both mouse strains. When nCuGTSM was administered, the Cmax was markedly higher, and the mean residence time was longer than when CuGTSM was administered for both CuGTSM and GTSM in both mouse strains. With macular mice, the AUC ratio (GTSM/CuGTSM) was markedly higher and the plasma CuGTSM concentration was lower than with C3H/HeNCrl mice when either CuGTSM or nCuGTSM was administered. CONCLUSION: Absorption of orally administered CuGTSM was confirmed in macular mice, and the nano-formulation improved the absorption and retention of CuGTSM in the body. However, the plasma concentration of CuGTSM was lower in macular mice than in control mice, suggesting easier dissociation of CuGTSM.

Advanced Formulation Design for Topical Creams Assisted with Vibrational Spectroscopic Imaging.

Vibrational spectroscopic imaging has become useful analytical tools for quality control of drug products. In this study, we applied microscopic attenuated total reflection (ATR)-IR and confocal Raman microscopy to elucidate microscopic structure of creams and for the formulation design in the development of semi-solid drug products. The model creams were prepared with prednisolone (PRD) and fluconazole (FLC) as active pharmaceutical ingredients and oily solvents such as mineral oil (MO), isopropyl myristate (IPM), benzyl alcohol (BA) and diethyl sebacate (DES). As a result of microscopic ATR-IR imaging, several domains indicating oily internal phase were observed, which had absorption around 1732 and 1734 cm-1 derived from MO, IPM and DES. In addition, domains of BA around 1009 cm-1 were observed at the complemental or similar position in the formulation with MO or DES, respectively. These results suggested that the creams were oil-in-water type and the distribution of domains would reflect the compatibility of the solvents. The contents of PRD and BA were determined quantitatively in each layer after the intentional separation of the creams and the results agreed well with the imaging analysis. Whereas, confocal Raman imaging allowed to visualize the distribution of the components in depth direction as well as two-dimensional plane. In particular, the Raman imaging would ensure the coexistence of FLC and BA as oily phase in the cream. From these results, the feasibility of spectroscopic imaging techniques was successfully demonstrated for the formulation design of semi-solid dosage forms.

Solid-State Analysis of Alpha-Cyclodextrin Inclusion Complexes Using Low-Frequency Raman Spectroscopy.

A rapid and nondestructive analytical technique is critical for the analysis of cyclodextrin inclusion complexes in solid dosage forms. This study proposed a newly developed low-frequency Raman spectroscopy as a candidate technique for the analysis of cyclodextrin inclusion complexes. In this study, we selected a typical series of five crystalline cyclodextrin inclusion complexes and reported the usefulness of Raman spectroscopy for analyzing these inclusion complexes. Some inclusion complexes clearly differed from the raw materials in conventional Raman spectra. In another case, though specific differences were not observed between inclusion complexes and raw materials in conventional Raman spectra, clear differences were observed in low-frequency Raman spectra. Moreover, no characteristic differences between inclusion complexes consisting of different guest molecules were observed in conventional Raman spectra. The characteristic differences were observed only in low-frequency Raman spectra. Therefore, low-frequency Raman spectroscopy is a useful technique for solid-state analysis of crystalline inclusion complexes.

Mechanistic study of preparation of drug/polymer/surfactant ternary hot extrudates to obtain small and stable drug nanocrystal suspensions.

We studied optimized conditions for preparing ternary hot extrudates (HEs) of glibenclamide (GLB)/polyvinylpyrrolidone (PVP)/sodium dodecyl sulfate to generate stable nanocrystal suspensions following aqueous dispersion. Raman and solid-state NMR measurements of ternary HEs prepared by altering HE conditions revealed that GLB crystallinity in HEs reduced with increased extrusion temperature and count and decreased screw speed. Aqueous dispersions of all HEs temporarily formed GLB nanoparticles with a diameter of 75-420 nm. The suspension from the HEs with the low GLB crystallinity (<22%) precipitated after 4-h storage, while the HEs with the high GLB crystallinity (>22%) formed stable nanocrystal suspension. Interestingly, the number of GLB nanoparticles <150  nm was different despite aqueous dispersion of HEs with similar GLB crystallinity, reflecting the different GLB crystalline size in those HEs. Although both the crushing by shear force and GLB dissolution into PVP reduced GLB crystalline size, the crushing GLB crystal by the shear force has a relatively high ability to decrease GLB crystalline size without excess amorphization of GLB. Performing the hot extrusion at a low temperature, a high screw speed, and maximizing extrusion count with GLB crystallinity >22% led to formation of small and stable nanocrystal suspensions.

[Pharmaceutical Properties of Anti-inflammatory Analgesic Patches Using Acrylic Polymer].

The mock patches were prepared with novel acrylic polymers as adhesive layer where biphenyl-4-ylacetic acid (BAA) or 2-(2-fluorobiphenyl-4-yl) propanoic acid (FPA) was used as model active pharmaceutical ingredients (APIs). In addition, the mock patches were formulated with typical ester ingredients for transdermal dosage forms. The molecular state of the model APIs in the adhesive layer was observed by polarized microscope and microscopic Raman spectroscopy, which contains both conventional and low frequency (LF) region. Crystallization behavior would be depended on the interaction between API and polymers in the adhesive layer. In particular, LF Raman measurement was useful to discriminate API polymorphs. The pharmaceutical properties including dissolution and skin permeation of APIs were also evaluated for mock patches. The drug release and transdermal permeation were enhanced with the ester ingredients such as isopropyl myristate and diethyl sebacate due to their diffusion to the test solution or the skin stratum corneum as well as reducing the interaction between API and polymers. Further, the tack strength was not changed, but the peel strength was weakened by the additives. Thus, the adhesive properties were controllable by formulation with the additives. These findings could enable to evaluate the interaction between API and the polymers for adhesive layer and select the appropriate polymer and additives for used APIs when designing the drug products.

Determining the Distribution of Active Pharmaceutical Ingredients in Combination Tablets Using Near IR and Low-Frequency Raman Spectroscopy Imaging.

Combination tablets containing multiple active pharmaceutical ingredients (APIs) are expected to improve patient convenience by decreasing the number of tablets to be taken; thus, numerous formulations containing multiple APIs have recently been developed. To allow for dose adjustments based on patient conditions, many tablets have a bisection line to allow equal division of tablets. However, there have been no investigations regarding content uniformity among divided combination tablets. Therefore, in this study, the content uniformity of combination tablets after division was investigated using near IR and low-frequency (LF) Raman spectroscopy imaging as well as the Japanese Pharmacopoeia (JP) content uniformity tests. As model drugs, five tablets of three combination drugs containing 3-(3,4-dihydroxyphenyl)-L-alanine (L-DOPA) and benserazide hydrochloride (BNS) as APIs for treating Parkinson's disease were bisected; the resultant 10 samples were subjected to the JP content uniformity tests. We found that acceptance values of L-DOPA and BNS were 11.0-21.9% and 13.3-17.5%, respectively, with some non-conformity to the maximum allowed acceptance value (15.0%) as per the current JP. Image analyses by near IR showed that L-DOPA, BNS, lactose, and corn starch were uniformly distributed in each tablet; moreover, LF Raman spectroscopy imaging also supported the result that L-DOPA, BNS, and lactose were evenly distributed. Therefore, drug content in the tablets was uniform; thus, careful manipulation was recommended in the tablet bisection. However, the results of bisection line specifications and hardness tests revealed that the ease of division differed depending on the tablets, which warrants attention.