Multivariate Quantification of the Solid State Phase Composition of Co-Amorphous Naproxen-Indomethacin

To benefit from the optimized dissolution properties of active pharmaceutical ingredients in their amorphous forms, co-amorphisation as a viable tool to stabilize these amorphous phases is of both academic and industrial interest. Reports dealing with the physical stability and recrystallization behavior of co-amorphous systems are however limited to qualitative evaluations based on the corresponding X-ray powder diffractograms. Therefore, the objective of the study was to develop a quantification model based on X-ray powder diffractometry (XRPD), followed by a multivariate partial least squares regression approach that enables the simultaneous determination of up to four solid state fractions: crystalline naproxen, γ-indomethacin, α-indomethacin as well as co-amorphous naproxen-indomethacin. For this purpose, a calibration set that covers the whole range of possible combinations of the four components was prepared and analyzed by XRPD. In order to test the model performances, leave-one-out cross validation was performed and revealed root mean square errors of validation between 3.11% and 3.45% for the crystalline molar fractions and 5.57% for the co-amorphous molar fraction. In summary, even four solid state phases, involving one co-amorphous phase, can be quantified with this XRPD data-based approach.

Nanoparticle agglomerates of indomethacin: The role of poloxamers and matrix former on their dissolution and aerosolisation efficiency

Nanoparticles (NPs) were prepared and assembled to microsized agglomerates with and without matrix formers (mannitol and L-leucine) by coupling wet milling and spray drying to harmonise the advantages of NPs with handling and aerodynamics of microparticles without induction of amorphisation. Indomethacin was selected as poorly water-soluble drug and poloxamers with different ratios of hydrophilic to hydrophobic domains were evaluated as stabilisers comparatively to D-α-Tocopherol polyethylene-glycol succinate (TPGS). Particle size of nanosuspensions and morphology, size, crystal form, drug loading, redispersibility, in vitro dissolution, and in vitro aerosolisation of NP-agglomerates were determined. Molecular weight of stabilisers affected the rate but not the limit of NP size reduction and the length of hydrophilic segment in poloxamers was found important for the nanosuspension stabilisation. SEM revealed the structure of agglomerates consisting of nanocrystal assemblies. XRPD with DSC proved that NP agglomerates retained their crystallinity. NP-agglomerates exhibited enhanced dissolution compared to physical mixtures of drug and stabilisers while incorporation of matrix formers enabled redispersibility upon hydration and further increased the drug dissolution. Also, matrix formers resulted in significantly improved aerosolisation with higher fine particle fractions (49-62%) and smaller mass median aerodynamic diameters (<3.5 μm), compared to cases without matrix formers (34-43% and <4.5 μm).

Role of simplex lattice statistical design in the formulation and optimization of microemulsions for transdermal delivery

Microemulsions (ME) have gained attention as an alternative pharmaceutical formulation for transdermal delivery systems. However, the complicated relationships between various ME compositions (causal factors) and their characteristics (response variable) have not been fully comprehended. To overcome this problem, the design and development of ME for transdermal delivery was performed in our study using Design Expert(®) Software. The model formulations of ME were prepared according to the ME region obtained from pseudo-ternary phase diagrams using the simplex lattice design as an optimization technique. In this study, ketoprofen-loaded ME composed of oleic acid, Cremophor(®) RH40, ethanol and water were prepared, and their characteristics (e.g., size, charge, conductivity, pH, viscosity, drug content, loading capacity and skin permeation flux) were evaluated. The ME having an appropriate skin permeation flux was used as the basis for optimization. The skin permeation flux of the experimental ME was very close to the flux predicted by Design Expert(®) Software and was significantly greater than that for the commercial product. Possible mechanisms for the enhancement of the skin permeation of the ME were also investigated using Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD). This finding provided an understanding of the relationship between the causal factors and response variables, as shown in the response surfaces. Moreover, these results indicated that the simple lattice design was beneficial for the pharmaceutical development of ME for transdermal delivery.

EFFECT OF INDOMETHACIN AND ITS COMPLEXES ON REPRODUCTIVE PERFORMANCE AND OXIDATIVE STRESS IN TESTIS AND STOMACH OF MALE ALBINO RATS WITH REFERENCE TO THEIR CHEMICAL CHARACTERIZATIONS

Four new complexes of Hg (II), Pb (II), Sn (II) and Bi (III) with indomethacin drug ligand (IMC) were synthesized and characterized by using infrared, electronic, 1H-NMR spectral, thermogravimetric and conductivity measurements. The IMC was found to act as bidentate chelating agent. IMC complexes coordinate through the oxygen of the carboxyl group. The molar ratio chelation is 1:2 (M2+:IMC) with general formula [M (IMC) 2], nH2O for Hg (II), Pb(II) and Sn(II), but 1:3 for Bi(III) ions. Antibacterial screening of these heavy metal complexes against Escherichia coli (Gram-ve), Bacillus subtilis (Gram +ve) and anti-fungi (Asperagillus oryzae, Asperagillus niger, Asperagillus Flavus) were investigated. In the present study, we found evidence suggesting that Bi+3/IMC possesses the capacity to protect the stomach, sperm, testes, cellular ATP, cellular NAD, INSL3, PGD2, PGE2 and antioxidant enzymes from deleterious actions of IMC.

Low-frequency vibrational properties of crystalline and glassy indomethacin probed by terahertz time-domain spectroscopy and low-frequency Raman scattering

In order to clarify the intermolecular vibrations, the low-frequency modes of the glassy and crystalline states of model pharmaceutical indomethacin have been studied using broadband terahertz time-domain spectroscopy and low-frequency Raman scattering. In the crystalline γ-form, the center of symmetry was suggested by the observation of the exclusion principle of the infrared (IR) and Raman selection rules in the frequency range between 0.2 and 6.5 THz. In addition, a boson peak of the glassy state was observed in both IR and Raman spectra and their frequency showed apparent discrepancy. The intermediate correlation length of the glassy structure was estimated to be about 2.5 nm. The existence of hydrogen bonded cyclic dimers in a glassy state was suggested by the observation of the infrared active intermolecular vibrational mode of the hydrogen bonded cyclic dimers as a broad peak at 3.0 THz in the IR spectrum.

Developing dissolution testing methodologies for extended-release oral dosage forms with supersaturating properties. Case example: Solid dispersion matrix of indomethacin

The objective of this study was to develop an in vitro dissolution test method with discrimination ability for an extended-release solid dispersion matrix of a lipophilic drug using the United States Pharmacopeia (USP) Apparatus 4, flow-through cell apparatus. In the open-loop configuration, the sink condition was maintained by manipulating the flow rate of the dissolution medium. To evaluate the testing conditions, the drug release mechanism from an extended-release solid dispersion matrix containing hydrophobic and hydrophilic polymers was investigated. As the hydroxypropyl methylcellulose (HPMC) maintained concentrations of indomethacin higher than the solubility in a dissolution medium, the release of HPMC into the dissolution medium was also quantified using size-exclusion chromatography. We concluded that the USP Apparatus 4 is suitable for application to an in vitro dissolution method for orally administered extended-release solid dispersion matrix formulations containing poorly water-soluble drugs.

Temperature-dependent drug release from DPPC:C12H25-PNIPAM-COOH liposomes: control of the drug loading/release by modulation of the nanocarriers' components

Novel polymer-modified thermosensitive liposomes were developed for the delivery of indomethacin in order to control its release profile. When attached to 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes, the end functionalized C12H25-poly(N-isopropylacrylamide)-COOH (C12H25-PNIPAM-COOH) polymer was membrane-disruptive in a temperature-dependent manner. The interest for this polymer is driven by its famous lower critical solution temperature (LCST) behavior, where heating an aqueous solution of PNIPAM above 32°C induces nanophase separation and polymer chain aggregation. The physicochemical/structural behavior of these polymer-modified thermosensitive liposomes was found to depend on the PNIPAM:lipid molar ratio and the composition of the polymeric guest. The incorporation of PNIPAM has caused alterations in the thermotropic behavior of DPPC liposomes, as the differential scanning calorimetry (DSC) experiments revealed. The drug loading and the release were found to be strongly dependent on the thermotropic characteristics of the PNIPAM grafted DPPC liposomes. Namely, the in vitro release is immediate at 37°C (>LCST) ("burst" effect), while the prepared mixed nanocarriers did not release the encapsulated bioactive substance at <32°C (<LCST). Thus, the thermosensitivity and the drug loading/release properties of the prepared formulations can be modulated by varying the ratio of DPPC/PNIPAM components, as well as the molecular characteristics of the polymeric guest.

Solid formulations by a nanocrystal approach: critical process parameters regarding scale-ability of nanocrystals for tableting applications

Nanocrystallization is among the foremost drug delivery platform approaches for the commercial development of poorly soluble drugs. There exists an urge to enable a universal shift of the production of the solid nanocrystal formulations from laboratory scale to industrially feasible scale. The success of any formulation development depends on its transferability to large scale manufacture. The objectives of the study were to increase the nanocrystallization batch size and to screen and optimize parameters for industrially feasible itraconazole (ITC) and indomethacin (IND) nanocrystal composition for tablet formulation. Thus, ITC and IND were transformed into nanocrystal suspensions, using an increased batch size of a wet milling process, freeze-dried, and further developed into both direct compression (DC) and granulated (G) tableting masses. According to the investigated powder and tablet properties (true density, flowability, dose uniformity, maximum upper punch force, crushing strength, dissolution and disintegration) and stability testings, it was clear that the amount of the nanocrystals in the solid tablet formulation is critical in order to fully utilize the benefits of the nanocrystals, i.e., fast dissolution, and to produce high-quality tablets. The DC designs of both the model drugs with compositions including 40% of freeze-dried nanocrystalline drug powder outperformed the corresponding granulated tablets in all parameters after the stability surveillance.

Fluorescent graphene oxide via polymer grafting: an efficient nanocarrier for both hydrophilic and hydrophobic drugs

Functionalized graphene-based drug delivery vehicles have conquered a significant position because functionalization improves its biocompatibility and stability in cell medium, leaving sufficient graphitic basal plane for drug loading through π-π stacking. In this study, poly(N-isopropylacrylamide) (PNIPAM) is covalently grafted from the surface of graphene oxide (GO) via a facile, eco-friendly and an easy procedure of free radical polymerization (FRP) using ammonium persulfate initiator. Various spectroscopic and microscopic studies confirm the successful grafting of PNIPAM from GO surface. PNIPAM-grafted GO (GPNM) exhibits enhanced thermal stability, improved dispersibility both in aqueous and cell medium, and better biocompatibility and cell viability compared to GO. Interestingly, GPNM displays an exciting fluorescence property in aqueous medium, which is a hike of intensity at 36 °C due to the lower critical solution temperature (LCST) of PNIPAM chains (32 °C). Moreover both hydrophilic (doxorubicin (DOX)) and hydrophobic (indomethacin (IMC)) drugs loaded on the surface of GPNM hybrid exhibits its efficacy as an efficient carrier for both types of drugs. Cellular uptakes of free DOX and DOX-loaded GPNM (GPNM-DOX) are evidenced both from optical and fluorescence imaging of live cells, and the efficiency of drug is significantly improved in the loaded system. The release of DOX from GPNM-DOX was achieved at pH 4, relevant to the environment of cancer cells. The pH-triggered release of hydrophobic drug was also studied using UV-vis spectroscopy via alginate encapsulation, showing a great enhancement at pH = 7.4. The IMC is also found to be released by human serum albumin using dialysis technique. The GPNM nanomaterial shows the property of simultaneous loading of DOX and IMC as well as pH-triggered simultaneous release of both of the drugs.

Role of fragility in the formation of highly stable organic glasses

In situ dielectric spectroscopy has been used to characterize vapor-deposited glasses of methyl-m-toluate (MMT), an organic glass former with low fragility (m = 60). Deposition near 0.84T(g) produces glasses of very high kinetic stability; these materials are comparable in stability to the most stable glasses produced from more fragile glass formers. Highly stable glasses of MMT, when annealed above T(g), transform into the supercooled liquid by a heterogeneous mechanism. A constant velocity propagating front is initiated at the free surface and controls the transformation of thin films. The transition to a bulk-dominated transformation process occurs at 5 μm, the largest length scale reported for any glass. Contrary to recent conclusions, we find that physical vapor deposition can form highly stable organic glasses across the entire range of liquid fragilities.

Evaluation of dysprosia aerogels as drug delivery systems: a comparative study with random and ordered mesoporous silicas

Biocompatible dysprosia aerogels were synthesized from DyCl3·6H2O and were reinforced mechanically with a conformal nano-thin-polyurea coating applied over their skeletal framework. The random mesoporous space of dysprosia aerogels was filled up to about 30% v/v with paracetamol, indomethacin, or insulin, and the drug release rate was monitored spectrophotometrically in phosphate buffer (pH = 7.4) or 0.1 M aqueous HCl. The drug uptake and release study was conducted comparatively with polyurea-crosslinked random silica aerogels, as well as with as-prepared (native) and polyurea-crosslinked mesoporous silica perforated with ordered 7 nm tubes in hexagonal packing. Drug uptake from random nanostructures (silica or dysprosia) was higher (30-35% w/w) and the release rate was slower (typically >20 h) relative to ordered silica (19-21% w/w, <1.5 h, respectively). Drug release data from dysprosia aerogels were fitted with a flux equation consisting of three additive terms that correspond to drug stored successively in three hierarchical pore sites on the skeletal framework. The high drug uptake and slow release from dysprosia aerogels, in combination with their low toxicity, strong paramagnetism, and the possibility for neutron activation render those materials attractive multifunctional vehicles for site-specific drug delivery.

Analysis of the molecular structure and vibrational spectra of the indole based analgesic drug indomethacin

The stability of the syn and anti structures of the non-steroidal anti-inflammatory drug indomethacin were investigated by the DFT-B3LYP and ab initio MP2 calculations with the 6-311G(**) basis set. The molecule was predicted at the DFT and MP2 levels of calculation to have the syn (C1N7C10C18 ∼40°) form being about 1.7 and 1.5kcal/mol, respectively lower in energy than the anti (C1N7C10C18 ∼140°) structure. The calculated CNCC torsional angles for the chlorobenzene and indole rings syn-anti conformational interconversion was in a good qualitative agreement with the reported X-ray angles (C1N7C10C18 ∼29 and 155°) for the syn and anti conformers, respectively). Indomethacin was estimated from the calculated Gibb's free energies to have an equilibrium mixture of 95% syn and 5% anti structures at 298.15K. The vibrational wavenumbers were computed at the B3LYP level of theory and complete vibrational assignments were provided on the basis of theoretical and normal coordinate calculations combined with experimental infrared and Raman data of the molecule. The analysis of the observed spectra supports the presence of indomethacin in only one conformation at room temperature.

Prostaglandin E2 (EP) receptors mediate PGE2-specific events in ovulation and luteinization within primate ovarian follicles

Prostaglandin E2 (PGE2) is a key mediator of ovulation. All 4 PGE2 receptors (EP receptors) are expressed in the primate follicle, but the specific role of each EP receptor in ovulatory events is poorly understood. To examine the ovulatory events mediated via these EP receptors, preovulatory monkey follicles were injected with vehicle, the PG synthesis inhibitor indomethacin, or indomethacin plus PGE2. An ovulatory dose of human chorionic gonadotropin was administered; the injected ovary was collected 48 hours later and serially sectioned. Vehicle-injected follicles showed normal ovulatory events, including follicle rupture, absence of an oocyte, and thickening of the granulosa cell layer. Indomethacin-injected follicles did not rupture and contained oocytes surrounded by unexpanded cumulus; granulosa cell hypertrophy did not occur. Follicles injected with indomethacin plus PGE2 were similar to vehicle-injected ovaries, indicating that PGE2 restored the ovulatory changes inhibited by indomethacin. Additional follicles were injected with indomethacin plus an agonist for each EP receptor. EP1, EP2, and EP4 agonists each promoted aspects of follicle rupture, but no single EP agonist recapitulated normal follicle rupture as seen in follicles injected with either vehicle or indomethacin plus PGE2. Although EP4 agonist-injected follicles contained oocytes in unexpanded cumulus, the absence of oocytes in EP1 agonist- and EP2 agonist-injected follicles suggests that these EP receptors promote cumulus expansion. Surprisingly, the EP3 agonist did not stimulate any of these ovulatory changes, despite the high level of EP3 receptor expression in the monkey follicle. Therefore, agonists and antagonists selective for EP1 and EP2 receptors hold the most promise for control of ovulatory events in women.

Confinement effects on drugs in thermally hydrocarbonized porous silicon

Thermally hydrocarbonized porous silicon (THCPSi) microparticles were loaded with indomethacin (IMC) and griseofulvin (GSV) using three different payloads between 6.2-19.5 and 6.2-11.4 wt %, respectively. The drug loading parameters were selected to avoid crystallization of the drug molecules on the external surface of the particles that would block the pore entrances. The successfulness of the loadings was verified with TG, DSC, and XRPD measurements. The effects of the confinement of IMC and GSV into the small mesopores of THCPSi were analyzed with helium pycnometry, FTIR, and NMR spectroscopy. The results showed the density of the THCPSi loaded drugs to be ca. 10% lower than the bulk crystalline forms, while a melt quenched amorphous drugs showed a density reduction of 3-7.5%. DSC and FTIR results confirmed that the drugs reside in an amorphous form within the THCPSi pores. Similar results were obtained with NMR, which also indicated that IMC may reside as both amorphous clusters and individual molecules within the pores. The (1)H transverse relaxation times (T2) of amorphous and THCPSi loaded drugs showed IMC relaxation times of 0.28 ms for both the cases, whereas for GSV the values were 0.32 and 0.39 ms, respectively, indicating similar limited mobility in both cases. The results indicated that strong drug-carrier interactions were not necessary for stabilizing the amorphous state of the adsorbed drug. Dissolution tests using biorelevant media, fasted state simulated intestinal fluid (FaSSIF) and simulated gastric fluid (SGF), showed that THCPSi-loaded IMC and GSV were rapidly released in FaSSIF with comparable rates to the amorphous forms, whereas in SGF the THCPSi reduced the pH dependency in the dissolution of IMC.

The effects of two polymeric matrices for indomethacin in cutaneous nociceptive reactivity in mice

AIM

This paper is focused on the investigation the effects of two polymeric matrices for indomethacin in cutaneous pain models in mice. There were used two different co-polymers polyhydroxyethyl methacrylate and undecan, polymerization reactions being conducted under nitrogen, at 80 degrees C.

MATERIAL AND METHODS

The experiments were carried out on white Swiss mice (20-25 g), divided into 6 groups of 7 animals each, treated orally. Biocompatibility properties of indomethacin-loaded copolymeric matrices ware evaluated by assessing the effects on the blood parameters, the serum biochemical tests of animals treated. The nociceptive somatic testing was performed using hot plate assay and tail immersion test. The latency (second) response to paw, respectively tail thermal noxious stimulation, was measured before the experiment and 15, 30, 60, 90, 120 minutes, 4, 6, 8, 10, 12 hours after the substances administration.

RESULTS

Laboratory analysis did not show significant differences of blood parameters, serum biochemical tests between control mice group (IND) and groups treated with 1 M, 1 IND, 3 M, 3 IND. In our experimental conditions IND determined a significant increasing of the latency period response, in hot plate and also in tail immersion tests. Using two different co-polymers for indomethacin incorporation we obtained an increasing of the latency time pain reaction in hot plate assay, respectively in tail immersion test, statistically significant (*p < 0.05) compared with the simple copolymers administration.

CONCLUSIONS

We demonstrated that indomethacin co-polymeric matrices 1 IND and 3 IND determined similar immune responses with indomethacin and simple co-polymers after oral administration in mice, indicative of good in vivo biocompatibility. Oral administration of both 1 IND and 3 IND resulted in prolonged antinociceptive effects in hot plate assay and also in tail immersion test in mice.

Polydimethylsiloxane-indomethacin blends and nanoparticles

A series of blends of polydimethylsiloxane (PDMS) and indomethacin (IMC), containing 20-80 wt.% IMC were obtained and characterized by differential scanning calorimetry, Fourier transform-infrared spectroscopy, and powder X-ray diffraction in order to observe the mutual influence of the two components. The main thermal transitions of PDMS remained un-changed. Both the solvent (tetrahydrofuran, THF) and the PDMS influenced the crystalline form of IMC. The blends were subsequently re-dissolved in THF, with or without cross-linking reagents added and precipitated into diluted aqueous solutions of siloxane-based surfactants. The resulted nanoparticles were analyzed by dynamic light scattering and scanning electron microscopy. Most of the particles had diameters between 200 and 300 nm. The surfactants, the IMC content and the cross-linking influenced the particles size and polydispersity, as well as the nanoparticle yield. The maximum drug release from selected aqueous formulations was 30%.

Electrospun upconversion composite fibers as dual drugs delivery system with individual release properties

Novel multifunctional poly(ε-caprolactone)-gelatin encapsulating upconversion core/shell silica nanoparticles (NPs) composite fibers as dual drugs delivery system (DDDS), with indomethacin (IMC) and doxorubicin (DOX) releasing in individual release properties, have been designed and fabricated via electrospinning process. Uniform and monodisperse upconversion (UC) luminescent NaYF4:Yb(3+), Er(3+) nanocrystals (UCNCs) were encapsulated with mesoporous silica shells, resulting in the formation of core/shell structured NaYF4:Yb(3+), Er(3+)@mSiO2 (UCNCs@mSiO2) NPs, which can be performed as DOX delivery carriers. These UCNCs@mSiO2 NPs loading DOX then were dispersed into the mixture of poly(ε-caprolactone) (PCL) and gelatin-based electrospinning solution containing IMC, followed by the preparation of dual drug-loaded composite fibers (DDDS) via electrospinning method. The drugs release profiles of the DDDS were measured, and the results indicated that the IMC and DOX released from the electrospun composite fibers showed distinct properties. The IMC in the composite fibers presented a fast release manner, while DOX showed a sustained release behavior. Moreover, the UC luminescent intensity ratios of (2)H(11/2)/(4)S(3/2)-(4)I(15/2) to (4)F(9/2)-(4)I(15/2) from Er(3+) vary with the amounts of DOX in the system, and thus drug release can be tracked and monitored by the luminescence resonance energy transfer (LRET) mechanism.

Real-time and in situ drug release monitoring from nanoporous implants under dynamic flow conditions by reflectometric interference spectroscopy

Herein, we present an innovative approach to monitoring in situ drug release under dynamic flow conditions from aluminum implants featuring nanoporous anodic alumina (NAA) covers used as a model of drug-releasing implants. In this method, reflectometric interference spectroscopy (RIfS) is used to monitor in real-time the diffusion of drug from these nanoporous implants. The release process is carried out in a microfluidic device, which makes it possible to analyze drug release under dynamic flow conditions with constant refreshing of eluting medium. This setup mimics the physiological conditions of biological milieu at the implant site inside the host body. The release of a model drug, indomethacin, is established by measuring the optical thickness change with time under four different flow rates (i.e. 0, 10, 30, and 50 μL min(-1)). The obtained data are fitted by a modified Higuchi model, confirming the diffusion-controlled release mechanism. The obtained release rate constants demonstrate that the drug release depends on the flow rate and the faster the flow rate the higher the drug release from the nanoporous covers. In particular, the rate constants increase from 2.23 ± 0.02 to 12.47 ± 0.04 μg min(-1/2) when the flow rate is increased from 10 to 50 μL min(-1), respectively. Therefore, this method provides more reliable and relevant information than conventional in vitro drug release methods performed under static conditions.

Indomethacin inhibits cancer cell migration via attenuation of cellular calcium mobilization

Non-steroidal anti-inflammatory drugs (NSAIDs) were shown to reduce the risk of colorectal cancer recurrence and are widely used to modulate inflammatory responses. Indomethacin is an NSAID. Herein, we reported that indomethacin can suppress cancer cell migration through its influence on the focal complexes formation. Furthermore, endothelial growth factor (EGF)-mediated Ca²⁺ influx was attenuated by indomethacin in a dose dependent manner. Our results identified a new mechanism of action for indomethacin: inhibition of calcium influx that is a key determinant of cancer cell migration.

Oxidation of non-steroidal anti-inflammatory drugs with aqueous permanganate

Potassium permanganate is a strong oxidant widely used in drinking water treatment, that can react with organic micropollutants. Thus, the oxidation kinetics and transformation route of seven non-steroidal anti-inflammatory drugs (NSAIDs) upon reaction with potassium permanganate was investigated. A liquid chromatography-quadrupole-time-of-flight-mass spectrometry (LC-Q-TOF-MS) system was used to follow the time course of pharmaceuticals concentrations and for the identification of their by-products. Under strong oxidation conditions (2 mg L(-1) KMnO4, 24 h), only two NSAIDs were significantly degraded: indomethacine and diclofenac. The degradation kinetics of these two drugs was investigated at different concentrations of permanganate, chlorides, phosphates and sample pH by means of a full factorial experimental design. Depending on these factors, half-lives were in the range: 2-270 h for indomethacine and 3-558 h for diclofenac, equivalent to apparent second order constants between 0.65 and 9.5 M(-1) s(-1) and 0.27 and 7.4 M(-1) s(-1), respectively. Permanganate concentration was the most significant factor on NSAIDs oxidation kinetics, but the pH also played a significant role in diclofenac reaction, being faster at acidic pH. In the case of indomethacine, the dose of permanganate seemed also to play an autocatalytic effect. The use of an accurate-mass high resolution LC-Q-TOF-MS system permitted the identification of a total of 13 by-products. The transformation path of these drugs consisted mainly of hydroxylations, decarboxylations and oxidation of aromatic double bonds, with ring opening. The software predicted toxicity of these products indicates that they are expected not to be more toxic than the NSAIDs, with the exception of two indomethacine by-products. Reaction in real samples was slower and/or incomplete for both pharmaceuticals, depending on the organic matter content of the sample. However, still all transformation products could be detected for indomethacine in permanganate treated surface water samples, and two out of five in the case of diclofenac.

[Mechanisms of hydroxypropyl methylcellulose for the precipitation inhibitor of supersaturatable self-emulsifying drug delivery systems]

Hydroxypropyl methylcellulose (HPMC) propels self-emulsifying drug delivery systems (SEDDS) to achieve the supersaturated state in gastrointestinal tract, which possesses important significance to enhance oral absorption for poorly water-soluble drugs. This study investigated capacities and mechanisms of HPMC with different viscosities (K4M, K15M and K100M) to inhibit drug precipitation of SEDDS in the simulated gastrointestinal tract environment in vitro. The results showed that HPMC inhibited drug precipitation during the dispersion of SEDDS under gastric conditions by inhibiting the formation of crystal nucleus and the growth of crystals. HPMC had evident effects on the rate of SEDDS lipolysis and benefited the distribution of drug molecules across into the aqueous phase and the decrease of drug sediment. The mechanisms were related to the formed network of HPMC and its viscosities and molecular weight. These results offered a reference for selecting appropriate type of HPMC as the precipitation inhibitor of supersaturatable SEDDS.

[The development of co-amorphous drug systems]

Converting two poorly water-soluble crystalline drugs to co-amorphous drug systems by ball milling, quench-cooling, or cryo-milling method can improve stability of the drug, enhance dissolution rates, and reduce adverse reactions of the single drug. Co-amorphous system has been used to solve problems of co-administration of medicines. Formation and intermolecular interactions of co-amorphous drug systems may be verified by differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), Raman spectroscopy (RS) and Fourier transform infrared spectroscopy (FT-IR). Stability of co-amorphous drug systems is influenced by their glass transition temperature (Tg) and intermolecular interactions. The theoretical Tg values and the interaction parameter x are calculated by Gordon-Taylor equation and the Flory-Huggins equation, respectively. Thus, co-amorphous drug systems are analyzed theoretically at molecular level. Co-amorphous drug systems provide a new sight for the co-administration of medicines.

Amino acids as co-amorphous stabilizers for poorly water-soluble drugs--Part 2: molecular interactions

The formation of co-amorphous drug-drug mixtures has proved to be a powerful approach to stabilize the amorphous form and at the same time increase the dissolution of poorly water-soluble drugs. Molecular interactions in these co-amorphous formulations can play a crucial role in stabilization and dissolution enhancement. In this regard, Fourier-transform infrared spectroscopy (FTIR) is a valuable tool to analyze the molecular near range order of the compounds in the co-amorphous mixtures. In this study, several co-amorphous drugs--low molecular weight excipient blends--have been analyzed with FTIR spectroscopy. Molecular interactions of the drugs carbamazepine and indomethacin with the amino acids arginine, phenylalanine, and tryptophan were investigated. The amino acids were chosen from the biological target site of both drugs and prepared as co-amorphous formulations together with the drugs by vibrational ball milling. A detailed analysis of the FTIR spectra of these formulations revealed specific peak shifts in the vibrational modes of functional groups of drug and amino acid, as long as one amino acid from the biological target site was present in the blends. These peak shifts indicate that the drugs formed specific molecular interactions (hydrogen bonding and π-π interactions) with the amino acids. In the drug-amino acid mixtures that contained amino acids which were not present at the biological target site, no such interactions were identified. This study shows the potential of amino acids as small molecular weight excipients in co-amorphous formulations to stabilize the amorphous form of a poorly water-soluble drug through strong and specific molecular interactions with the drug.

Metabolism of BYZX in human liver microsomes and cytosol: identification of the metabolites and metabolic pathways of BYZX

BYZX, [(E)-2-(4-((diethylamino)methyl)benzylidene)-5,6-dimethoxy-2,3-dihydroinden-one], belongs to a series of novel acetylcholinesterase inhibitors and has been synthesized as a new chemical entity for the treatment of Alzheimer’s disease symptoms. When incubated with human liver microsomes (HLMs), BYZX was rapidly transformed into its metabolites M1, M2, and M3. The chemical structures of these metabolites were identified using liquid chromatography tandem mass spectrometry and nuclear magnetic resonance, which indicated that M1 was an N-desethylated and C = C hydrogenation metabolite of BYZX. M2 and M3 were 2 precursor metabolites, which resulted from the hydrogenation and desethylation of BYZX, respectively. Further studies with chemical inhibitors and human recombinant cytochrome P450s (CYPs), and correlation studies were performed. The results indicated that the N-desethylation of BYZX and M2 was mediated by CYP3A4 and CYP2C8. The reduced form of β-nicotinamide adenine dinucleotide 2′-phosphate was involved in the hydrogenation of BYZX and M3, and this reaction occurred in the HLMs and in the human liver cytosol. The hydrogenation reaction was not inhibited by any chemical inhibitors of CYPs, but it was significantly inhibited by some substrates of α,β-ketoalkene C = C reductases and their inhibitors such as benzylideneacetone, dicoumarol, and indomethacin. Our results suggest that α,β-ketoalkene C = C reductases may play a role in the hydrogenation reaction, but this issue requires further clarification.