Spectrophotometric determination of fenoprofen calcium drug in pure and pharmaceutical preparations. Spectroscopic characterization of the charge transfer solid complexes

Simple, accurate and robust spectrophotometric method was developed for determination of fenoprofen calcium drug (FPC). The proposed method was based on the charge transfer (CT) reaction of FPC drug (as n-electron donor) with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 2,4,6-trinitrophenol (picric acid, PA) or 1,2,5,8-tetrahydroxyanthraquinone (Quinalizarin, QZ) (as π-acceptors) to give highly colored charge transfer complexes. Different variables affecting the reaction such as reagent concentration, temperature and time have been carefully optimized to achieve the highest sensitivity. Beer's law was obeyed over the concentration ranges of 2-60, 0.6-90 and 4-30μgmL^-1 using DDQ, PA and QZ CT reagents, respectively, with correlation coefficients of 0.9986, 0.9989 and 0.997 and detection limits of 1.78, 0.48 and 2.6μgmL^-1 for the CT reagents in the same order. Elucidation of the chemical structure of the solid CT complexes formed via reaction between the drug under study and π-acceptors was done using elemental, thermal analyses, IR, ¹H NMR and mass spectrometry. X-ray diffraction was used to estimate the crystallinity of the CT complexes. Their biological activities were screened against different bacterial and fungal organisms. The method was applied successfully with satisfactory results for the determination of FPC drug in fenoprofen capsules. The method was validated with respect to linearity, limit of detection and quantification, inter- and intra-days precision and accuracy. The proposed method gave comparable results with the official method.

Rapid simultaneous determination of four non-steroidal anti-inflammatory drugs by means of derivative nonlinear variable-angle synchronous fluorescence spectrometry

A rapid, simple, and inexpensive spectrofluorimetric method has been proposed for the simultaneous quantification of diflunisal, salicylic acid, fenoprofen, and 6-methoxy-2-naphthylacetic acid (6MNA). First-derivative nonlinear variable-angle synchronous fluorescence spectrometry has been developed to improve the selectivity of fluorescence measurements without loss of sensitivity. It allows the simultaneous determination of different substances in a mixture from a single spectrum based on a single scan. The analyses were performed in an ethanol-water (70%) medium at a pH of 9.2, adjusted by using ammonium/ammonia (0.5 M) as a buffer solution. The linear concentration ranges are 30.0-100.0, 100.0-600.0, 50.0-150.0, and 30.0-100.0 ng/mL for salicylic acid, fenoprofen, diflunisal, and 6-methoxy-2-naphthylacetic acid, respectively, at lambda(ex)/lambda(em) = 281.1/423.6, 241.2/301.2, 284.1/403.8, and 268.7/339.6 nm, respectively. Analytical parameters of the proposed method were calculated according to the error propagation theory. The sensitivity, repeatability, reproducibility, and limits of detection achieved with the proposed method are adequate for the determination of these anti-inflammatory drugs.

Removal of selected pharmaceuticals by chlorination, coagulation-sedimentation and powdered activated carbon treatment

Removal property of nine pharmaceuticals (clofibric acid, diclofenac, fenoprofen, gemfibrozil, ibuprofen, indomethacin, ketoprofen, naproxen and propyphenazone) by chlorination, coagulation-sedimentation and powdered activated carbon treatment was examined by laboratory-scale experiments under the conditions close to actual drinking water treatment processes. Indomethacin and propyphenazone were completely degraded by chlorination within 30 minutes, but others remained around 30% (naproxen and diclofenac) or more than 80% of the initial concentration after 24 hours. A couple of unidentified peaks in a chromatogram of the chlorinated samples suggested the formation of unknown chlorination by-products. Competitive adsorption was observed when the mixed solution of the target pharmaceuticals was subjected to batch adsorption test with powdered activated carbon. Clofibric acid and ibuprofen, which were relatively less hydrophobic among the nine compounds, persisted around 60% of the initial concentration after 3 hours of contact time. Removal performance in actual drinking water treatment would become lower due to existence of other competitive substances in raw water (e.g. natural organic matter). Coagulation-sedimentation using polyaluminium chloride hardly removed most of the pharmaceuticals even under its optimal dose for turbidity removal. It is suggested that the most part of pharmaceuticals in raw water might persist in the course of conventional drinking water treatments.

Stereoselective disposition of fenoprofen in plasma and synovial fluid of patients with rheumatoid arthritis

The simultaneous disposition of fenoprofen enantiomers in synovial fluid and plasma was studied in 11 patients with arthritis and chronic knee effusions treated with a single oral dose of 600 mg rac-fenoprofen. A plasma sample and a synovial fluid sample were collected simultaneously from each patient up to 16 h after the administration of fenoprofen. A stereospecific assay for fenoprofen using LC-MS-MS was developed and applied successfully to the analysis of the enantiomers in plasma (LOQ = 10 ng of each enantiomer/ml) and synovial fluid (LOQ = 25 ng of each enantiomer/ml). The values of the area under the curve (AUC) for the S-(+)-fenoprofen eutomer were approximately 2.5 times higher in plasma than in synovial fluid (256 vs 104 microg h/ml), while the values for the R-(-)-fenoprofen distomer were about four times higher in plasma than in synovial fluid (42.5 vs 10.5 microg h/ml). These data demonstrate accumulation of the S-(+)-fenoprofen eutomer in plasma and in synovial fluid, with concentrations versus time AUC (+)/(-) ratios of 6.0 in plasma and 9.9 in synovial fluid, suggesting a greater accumulation of the eutomer at the active site represented by synovial fluid than in plasma. This result demonstrates the importance of enantioselective methods and of analysis of synovial fluid rather than plasma in studies of the pharmacokinetics-pharmacodynamics of fenoprofen.

Fenoprofen and Ketoprofen Amides as Potential Antitumor Agents

Following numerous experimental observations that various non-steroidal anti-inflammatory drugs have antitumor potentials, a series of fenoprofenamides (1a-g) and ketoprofenamides (2a-c) was tested on proliferation of different human tumor cell lines and normal human fibroblasts in vitro. Fenoprofen and ketoprofen showed modest antiproliferative activity, whereas the growth inhibitory activity of the tested amides clearly demonstrates that the substituents linked by an amide bond are essential for the significantly stronger cytostatic activity, probably because of a greater lipophilicity and/or better cell uptake. Additionally, it was shown that the most active derivatives (1d and 2a) induced cell cycle arrest at the G1 phase, as well as apoptosis.

Interaction of ibuprofen and other structurally related NSAIDs with the sodium-coupled monocarboxylate transporter SMCT1 (SLC5A8)

PURPOSE

Sodium-coupled monocarboxylate transporter 1 (SMCT1) is a Na+-coupled transporter for monocarboxylates. Many nonsteroidal anti-inflammatory drugs (NSAIDs) are monocarboxylates. Therefore, we investigated the interaction of these drugs with human SMCT1 (hSMCT1).

METHODS

We expressed hSMCT1 in a mammalian cell line and in Xenopus laevis oocytes and used the uptake of nicotinate and propionate-induced currents to monitor its transport function, respectively. We also used [14C]-nicotinate and [3H]-ibuprofen for direct measurements of uptake in oocytes.

RESULTS

In mammalian cells, hSMCT1-mediated nicotinate uptake was inhibited by ibuprofen and other structurally related NSAIDs. The inhibition was Na+ dependent. With ibuprofen, the concentration necessary for 50% inhibition was 64 +/- 16 microM. In oocytes, the transport function of hSMCT1 was associated with inward currents in the presence of propionate. Under identical conditions, ibuprofen and other structurally related NSAIDs failed to induce inward currents. However, these compounds blocked propionate-induced currents. With ibuprofen, the blockade was dose dependent, Na+ dependent, and competitive. However, there was no uptake of [3H]-ibuprofen into oocytes expressing hSMCT1, although the uptake of [14C]-nicotinate was demonstrable under identical conditions.

CONCLUSIONS

Ibuprofen and other structurally related NSAIDs interact with hSMCT1 as blockers of its transport function rather than as its transportable substrates.

Pharmaceutical liquid crystals: the relevance of partially ordered systems

Pharmaceutical solids have generally been characterized as either three-dimensional crystals or amorphous solids based on X-ray powder diffraction and modulated temperature differential scanning calorimetry. In contrast, fewer examples of thermotropic and lyotropic liquid crystals, or mesophases, appear in the pharmaceutical literature, and that literature teaches that the aforementioned analytical techniques should be complemented with polarized light microscopy and small-angle X-ray scattering in order to effectively identify potential liquid crystalline states. Lyotropic liquid crystals are induced by the presence of solvent, and have been extensively described elsewhere in the context of emulsion technology; however, other pharmaceutical examples are emerging. Thermotropic liquid crystals are induced by a change in temperature and are essentially free of solvent, where more pharmaceutical applications appear in the literature. In the present review the general structural characteristics that favor the formation of liquid crystalline mesophases are categorized by therapeutic target and molecular size, and the analytical means of their identification are presented.

Synthesis of fenoprofen and gemfibrozil styrene-maleic acid copolymer conjugates

Two types of polymer-drug conjugates were synthesized starting from styrene-maleic acid anhydride copolymer (SMA). Fenoprofen and gemfibrozil were chosen as model drugs because of their short plasma half lives. Both drugs were first converted to their 2-aminoethylamides, which possess free amino groups capable of reacting with SMA anhydride rings. By modifying the degree and type of substitution, lipophilic and hydrophilic conjugates were obtained. Drug loading in the conjugates was between 17 and 47%.

Enantioselective Kinetic Disposition of Fenoprofen in Rats with Experimental Diabetes or Adjuvant-Induced Arthritis

This study was aimed to investigate the influence of diabetes or arthritis on the enantioselective metabolism and kinetic disposition of fenoprofen in rats with streptozotocin-induced diabetes or Mycobacteriumtuberculosis adjuvant-induced arthritis. Animals received i.v. 10 mg/kg racemic fenoprofen and blood samples were collected up to 24 h thereafter, with 5 animals studied at each time point. Plasma concentrations of the fenoprofen enantiomers were determined by HPLC. Diabetic and arthritic animals showed significant differences when compared with respective controls for the following pharmacokinetic variables of the (+)-(S)-fenoprofen eutomer: area under the plasma concentration time curve, total clearance and volume of distribution. The results indicate that experimental diabetes and adjuvant-induced arthritis influence the fenoprofen enantioselective metabolism.

Influence of rheumatoid arthritis in the enantioselective disposition of fenoprofen

To investigate the influence of rheumatoid arthritis on the stereoselective disposition of fenoprofen administered as a racemic mixture, eight patients with rheumatoid arthritis receiving calcium rac-fenoprofen (200 mg/8 h) and 7 healthy volunteers given single oral dose (600 mg) were investigated. Serial blood samples and urine were collected from zero to 24 h after fenoprofen (FEN) administration. The following differences were observed between the (+)-(S) and (-)-(R)-FEN in the patients with rheumatoid arthritis (means 95% CI, Wilcoxon test, P < 0.05): C(max) 14.1 (12.5-15.8) versus 3.6 (2.5-4.7) microg/ml; AUC(ss) (0-8) 80.5 (67.3-93.7) versus 12.1 (8.8-15.4) microg.h/ml; Cl(T)/f 1.3 (1.0-1.5) versus 9.1 (6.5-11.8) l/h; and t(1/2) 3.1 (2.3-3.9) versus 1.2 (0.8-1.6) h. The Cl(T)/f of (-)-(R)-FEN was reduced in patients with rheumatoid arthritis when compared to healthy volunteers: 9.1 (6.5-11.8) versus 17.4 (13.9-20.9) l/h; P < 0.05 Mann-Whitney test. The administration of rac-FEN as a single dose to healthy volunteers or multiple doses to patients with rheumatoid arthritis resulted in lower Cl(T)/f for the (+)-(S)-FEN. The lower Cl(T)/f of (-)-(R)-FEN observed for patients with rheumatoid arthritis is consistent with lower clearance by inversion, although other metabolic pathways, drug interactions, and bioavailability of the individual enantiomers may also contribute to the difference.

Physical stability and solubility of the thermotropic mesophase of fenoprofen calcium as pure drug and in a tablet formulation

The aim of this study was to investigate and compare the physical stability and solubility of the liquid crystalline form of fenoprofen calcium as pure drug and in a proprietary tablet formulation (Nalfon), and to investigate if a simple heat treatment of a proprietary tablet containing fenoprofen calcium may lead to a physically stable formulation with enhanced dissolution rate and apparent solubility. The liquid crystalline form of fenoprofen calcium (thermotropic mesophase) was prepared by heating the crystalline drug to 125 degrees C to remove the water of crystallisation. Differential scanning calorimetry investigation revealed an endothermic peak at 89 degrees C upon heating (liquid crystal formation) attributable to water loss from the crystalline dihydrate. The liquid crystalline order was maintained upon cooling. No interference of tablet excipients with the thermal behaviour of the drug in the tablet formulation was observed. The crystalline dihydrate and liquid crystalline forms of fenoprofen calcium could be differentiated by diffuse reflectance infra-red spectroscopy and X-ray powder diffraction, both as pure drug and in tablet formulation. The supercooled liquid crystal (thermotropic reversed hexagonal phase) alone and in preheated and ground tablets was physically stable when stored in a dry environment or at 33% relative humidities (RH) at both 20 and 40 degrees C for 2 months. At 40 degrees C and 75% RH the supercooled mesophase extensively converted to the crystalline dihydrate within 6 days. Liquid crystalline fenoprofen calcium stored at 20 degrees C and 75% RH showed only partial dihydrate conversion after 2 months of storage. The solubility of the crystalline dihydrate alone and from the tablet formulation was 2.8+/-0.2 mg/ml and 3.0+/-0.2 mg/ml (mean+/-s.d.), respectively, (not significantly different), whereas the maximum solubility of the liquid crystal was 5.0+/-0.3 mg/ml (mean+/-s.d.) and 6.9+/-0.6 mg/ml (mean+/-s.d.), respectively (significantly different). The difference in maximum solubility between the crystalline dihydrate form of fenoprofen calcium and the fenoprofen calcium mesophase was highly significant, for both the pure drugs and the tablet formulations. The dissolution rate of the liquid crystalline fenoprofen calcium in preheated, intact tablets was significantly lower than that of the crystalline form in non-preheated tablets. Gross visual changes and scanning electron microscopy indicated that the disintegration properties of the tablet may be detrimentally effected by heating the tablet to 125 degrees C, diminishing the beneficial effect of improved solubility of the liquid crystal. The study has shown that conversion of the crystalline form of fenoprofen calcium to the liquid crystal can enhance the apparent solubility of the pure drug and the drug in presence of tablet excipients, but that the conversion should be performed before tablet formulation in order to increase dissolution of this poorly water-soluble drug.

Macromolecular prodrugs: X. Kinetics of fenoprofen release from PHEA-fenoprofen conjugate

The kinetics of fenoprofen release from poly[alpha,beta-(N-2-hydroxyethyl-DL-aspartamide)]-fenoprofen conjugate (PHEA-Fen) in aqueous buffer solutions (pH 10 and 1.1), simulated gastric (SGF) and intestinal fluids (SIF) was studied. In borate buffer pH 10, the following rate constants were obtained: k=0.2659 (t=60 degrees C) and k=0.0177 h(-1) (t=37 degrees C) and in glycine buffer solution pH 1.1 k=0.0036 h(-1). In SGF and SIF fenoprofen release did not occur in significant extend within 12 h. The hydrolysis of the ester bond between the polymeric carrier and fenoprofen followed the pseudo first-order kinetics, with activation energy indicative for the breakage of a sigma bond (E(a)=100.6 kJ mol(-1)). The concentration of the released fenoprofen was determined by high performance liquid chromatography (HPLC).

Chiral inversion of (R)-(-)-fenoprofen in guinea-pigs pretreated with clofibrate

The influence of clofibrate on the stereoconversion of fenoprofen (FPF) was studied in guinea pigs. This hypolipidaemic agent has been related to some biochemical changes in the liver leading to an increase in the chiral inversion process. Two groups of animals (n = 6 per group) were pretreated with oral doses of clofibrate (280 mg/kg per day) for three days and were then given (R)- or (S)-FPF (5 mg/kg, IV). The FPF enantiomers were extracted from the guinea-pigs' plasma using a solid phase procedure and analysed by HPLC with previous derivatization with L-leucinamide. Pretreatment with clofibrate increased the chiral inversion of (R)-FPF in favour of the pharmacologically active (S)-FPF enantiomer. Before this metabolic interaction can be applied to therapy with fenoprofen, the toxic effects of (S)-(+)-FPF on the gastrointestinal and renal tracts and the interference by (R)-(-)-FPF with the metabolism of lipids should be thoroughly evaluated.

Macromolecular prodrugs. IX. Synthesis of polymer-fenoprofen conjugates

Synthesis of several polymer-fenoprofen conjugates is described. Fenoprofen was first chemically modified into benzotriazolide 2 and amino acid amide derivatives: glycine fenoprofenamide (3a) and beta-alanine fenoprofenamide (3b) and their benzotriazolides 6a and 6b. Compounds 2 and 6 readily reacted with polyhydroxy aspartamide-type polymers, i.e. poly[alpha,beta-(N-2-hydroxyethyl-DL-aspartamide)] (PHEA) and poly[alpha,beta-(N-3-hydroxypropyl-DL-aspartamide)] (PHPA) forming conjugates 5, 8a,b and 9a,b, respectively. Conjugate 11 was obtained by partial aminolysis of poly-DL-(2,5-dioxo-1,3-pyrrolidinediyl) (PSI) with 2-aminoethyl fenoprofenamide (3c), followed by total aminolysis with 2-hydroxyethylamine. The synthesised polymer-drug conjugates differed in type of covalent bounding, type and/or length of spacer and drug-loading.

Dehydration, hydration behavior, and structural analysis of fenoprofen calcium

Fenoprofen calcium (FC) is a nonsteroidal, anti-inflammatory, analgesic, and antipyretic agent. The dehydration behavior of FC dihydrate and the rehydration of the dried FC were investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and powder X-ray diffractometry (PXRD). The stoichiometry, the crystal packing arrangement, and water environments in FC dihydrate were determined using single-crystal X-ray diffraction (XRD) analysis. The Arrhenius plot (natural logarithm of the dehydration rate constant versus the reciprocal of absolute temperature) for FC dihydrate from isothermal TGA is not linear. The activation energy of dehydration was 309 kJ/mol in the 50-60 degrees C range and 123 kJ/mol in the 60-80 degrees C range. The difference in activation energy can be explained from the crystal structure data where one water molecule is sandwiched between repeating polar carboxylate groups and the other water is in a slightly less polar region of the crystal. Single-crystal XRD analysis also indicated each calcium ion is coordinated to six oxygens. Two coordinating oxygens are provided by two water molecules and the other four oxygens are provided by the carboxylate group of four separate fenoprofen anions. Each fenoprofen anion, which can provide two oxygens for coordination, is associated with two different calcium ions. Hot-stage PXRD suggested that only a loss of 1 mole of water per mole of FC dihydrate (forming a monohydrate) was required to convert the material to a partially crystalline state. The monohydrate is not completely disordered as evidenced by a strong diffraction peak as well as some weaker peaks in the PXRD pattern. The rehydration of the anhydrous form of FC follows a solution-mediated transformation, prior to crystallizing as the dihydrate.

[Study on the release mechanism of fenoprofen calcium from hydrophillic sustained-release matrix]

AIM

To study the release mechanism of fenoprofen calcium (FC) from hydroxypropylmethylcellulose (HPMC) matrices.

METHODS

The release of FC and the erosion properties of hydrophillic matrices containing HPMC was examined at different paddle speed. The release mechanism of FC was further confirmed by evaluating the n value in Peppas equation.

RESULTS

The results indicate that the release of FC and the erosion of matrices exhibit zero order kinetic equation, and it exhibits line relationship between them.

CONCLUSION

In the first 40 min, FC mainly released by diffusion and erosion from HPMC matrix, while it was controlled by the rate of tablet erosion after 50 min.

Synthesis and characteristics of the human serum albumin-triazine chiral stationary phase

Human serum albumin (HSA) was successfully bonded to silica with s-triazine as activator. The coupling reaction by this method was rapid and effective. The triazine-activated silica is relatively stable and can be installed for at least 1 month without obvious loss of reactivity when stored below 30 degrees C, pH below 7. It was observed that the amount of bound HSA reached 120 mg/g silica calculated from the UV absorbance difference of the HSA solution. d, l-tryptophan was selected as the probe solute to characterize the properties of HSA bonded s-triazine chiral stationary phase, and separation factor of 9.4 was obtained for d,l-tryptophan. Furthermore, the amount of effective HSA on silica was measured by high-performance frontal analysis, and only 16.8 mg/g silica was responsible for the resolution of d,l-tryptophan. These results indicate that the amount of both the bound and effective HSA on silica with triazine as activator was much higher than those by the Schiff base coupling method. Different kinds of enantiomers were resolved successfully on the aminopropylsilica-bonded HSA s-triazine chiral stationary phase.

Chiral inversion of R(-) fenoprofen and ketoprofen enantiomers in cats

The chiral inversion process is a characteristic metabolic pathway for different aryl-2-propionic acids or profens. Important variations have been observed between these individual compounds as well as between animal species. In this study, R(-) fenoprofen [R(-)FPF] and R(-) ketoprofen [R(-) KTF] were used to investigate their comparative stereoconversion in cats. After intravenous (i.v.) administration of R(-) FPF, the percentage of chiral inversion was 93.20+/-13.70%. A highly significant correlation (r: 0.978) was observed between the clearance of R(-) FPF and the chiral inversion process. After i.v. administration of R(-) KTF, the percentage of inversion was only 36.73+/-2.8%. No correlation between the clearance of R(-) KTF and this process was observed. R(-) FPF was metabolized by the pathways of thioesterification - chiral inversion processes. For R(-) KTF, the competitive metabolic pathways, glucuronidation and hydroxylation may be involved. However, these metabolic steps are saturable or less functional in cats. Moreover, the thioesterification of R(-) KTF in in vitro studies has been shown to be important in carnivores. The lack of correlation between clearance and chiral inversion process of R(-) KTF may be finally explained by deviation of thioesterification to other metabolic pathways of lipids and/or aminoacid conjugation, particulary glicine derivatives.

Monte Carlo simulations of the chiral recognition of fenoprofen enantiomers by cyclomaltoheptaose (beta-cyclodextrin)

Differential complexation of fenoprofen enantiomers by cyclomaltoheptaose (beta-cyclodextrin) was investigated by Monte Carlo docking simulations. The chiral discrimination of (R)- and (S)-fenoprofen by beta-cyclodextrin was discussed in terms of the difference in the interaction energies and the patterns of molecular interactions. The interaction energies between each enantiomer of fenoprofen and beta-cyclodextrin were consistent with the reported experimental results that showed that the S isomer interacted preferentially with beta-cyclodextrin and was retained longer in a separation process than the R isomer. The thermodynamic preference of inclusion complex formation of (S)-fenoprofen could be explained by the orientation of the phenyl group attached to the chiral carbon, which provided closer contact and thus more favorable intermolecular interactions between the host and guest molecule. The results presented here would be very useful for the prediction of chiral recognition ability of beta-cyclodextrin.

Structural relationship and desolvation behavior of cromolyn, cefazolin and fenoprofen sodium hydrates

The hydrated crystal structures of cromolyn, cefazolin, and fenoprofen sodium salts are reported. The former two compounds are non-stoichiometric hydrates, whereas the fenoprofen lattice maintains its stoichiometry over a broad range of relative humidity. The relationship between composition, lattice parameters, and relative humidity is studied using a combination of moisture sorption isotherms and variable humidity X-ray powder diffraction. The dehydration properties of the sodium salts are related to the ion coordination and hydrogen bonding of the water molecules in the structures. Anisotropic lattice contraction is observed during dehydration of the cromolyn and cefazolin sodium and is related to the closeness of intermolecular contacts in the hydrated structures.

Study of the binding in an aqueous medium of inclusion complexes of several cyclodextrins involving fenoprofen calcium

Interactions among fenoprofen calcium and alpha-, beta-, gamma- and hydroxypropyl-beta-cyclodextrins (HP-beta-CD) were evaluated in aqueous solution by UV/vis and fluorescence direct spectroscopies and monodimensional (1D) 1H-NMR. Different UV/vis and fluorescence emission spectra were obtained to study the apparent binding constants (K) to define the most appropriate cyclodextrin to form the inclusion complexes (IC). beta-CD and HP-beta-CD clearly fit the magnitude of stability constant data of the complexes to take into account the pharmaceutical technology interest.

Interactions between fenoprofen sodium and poly (ethylene oxide)

Interactions of the amphiphilic drug fenoprofen sodium (FNa) in solution below and above its critical micelle concentration with poly (ethylene oxide) (PEO) of different chain length (PEO 400 to PEO 20000) and between a liquid crystalline formulation of fenoprofen (FLC; containing FNa, fenoprofen acid and water) and PEO were investigated, using surface tension measurements, viscometry, cloud point temperature measurements, [1H]NMR, polarised light microscopy, transmission electron microscopy, and differential scanning calorimetry. Interaction between FNa solutions and PEO: the investigations suggest that an interaction starts below the critical micelle concentration (CMC) of FNa. This can be concluded from [1H]NMR experiments (an upfield shift of the PEO proton signal was found at FNa concentrations below the CMC of FNa), surface tension measurements (absence of a critical association concentration) and cloud point temperature determinations. The surfactant does not seem to bind quantitatively on the PEO molecules (a higher FNa concentration was needed to cause the same upfield shift of the PEO proton signal than for more lipophilic surfactants, and no plateau phase in the surface tension reduction isotherm could be determined). Interactions were found to be independent from the chain length of the PEO. Interactions between FLC and PEO/pluronics: partial or complete dissolution of the fenoprofen mesophase (detected by [1H]NMR, polarised light microscopy and transmission electron microscopy) occurred after addition of PEO at concentrations between 2 and 10% (w/w), independent from the molecular weight of the PEO. A comparable amount of water added to the liquid crystalline samples does not change the mesophase into a liquid crystalline dispersion or a micellar solution. The liquid crystalline particles in the dispersion formed by the addition of PEO, had a higher transition temperature into an isotropic phase (between 54 degrees C and 57 degrees C), than in liquid crystalline dispersions without polymer (40 degrees C). The interactions between FNa and PEO can be interpreted in terms of a hydrophobic interaction with an association of the drug molecules on the polymer, i.e. the interaction between FNa and PEO occurs at a molecular rather than a micellar level. The interaction leads to a dissolution of the fenoprofen liquid crystal and the formation of an isotropic phase. No phase separation of the oily, amorphous, practically water insoluble fenoprofen acid could be found. Addition of PEO also seems to affect the composition of the remaining mesophase.

Separation of profen enantiomers by capillary electrophoresis using cyclodextrins as chiral selectors

A method for resolving the enantiomers of various 2-arylpropionic acids (viz. ketoprofen, ibuprofen and fenoprofen) by capillary zone electrophoresis (CZE) using a background electrolyte (BGE) containing a cyclodextrin as chiral selector is proposed. The effects of the type of cyclodextrin used and its concentration on resolution were studied and heptakis-2,3,6-tri- O-methyl-beta-cyclodextrin was found to be the sole effective choice for the quantitative enantiomeric resolution of all the compounds tested. The influence of pH, BGE concentration, capillary temperature and addition of methanol to the BGE on resolution and other separation-related parameters was also studied. The three compounds studied can be enantiomerically resolved with a high efficiency in a short time (less than 20 min) with no capillary treatment. This makes the proposed method suitable for assessing the enantiomeric purity of commercially available pharmaceuticals.

Multi-site binding of fenoprofen to human serum albumin studied by a combined technique of microdialysis with high performance liquid chromatography

A simple and fast method for the determination of the multi-site binding of fenoprofen (FP) to human serum albumin (HSA) has been developed by utilizing microdialysis sampling techniques combined with high performance liquid chromatography (HPLC). The drug and protein were mixed in different molar ratios in 0.067 Mol potassium phosphate buffer, pH 7.4, and incubated at 37 degrees C in a water-bath. Then the microdialysis probe was put in the FP-HSA solution and sampled at the perfusion rate of 1 microL/min. The concentrations of FP in microdialysates were determined by the reversed-phase high performance liquid chromatography. Relative recovery (R) was also determined in vitro on similar condition, R is about 56.03 +/- 1.11% (n = 3). Fenoprofen was found to bind to two classes of sites, the association constant (K1) and the number of the binding sites on primary binding sites of a HSA molecule (n1) for fenoprofen are 3.4 x 10(5)/M and 2.5, respectively, and those for secondary binding are 1.0 x 10(4)/M and 10.0, respectively. The competitive interaction of ibuprofen (IP) and palmitic acid with fenoprofen to HSA were also studied, both compounds significantly decrease the binding degree of fenoprofen to HSA.

(-)-R-fenoprofen: formation of fenoprofenyl-coenzyme A by rat liver microsomes

The thioesterification of fenoprofen (FPF) by rat liver microsomes has been studied using an HPLC method enabling direct quantification of the FPF-CoA produced. Over the concentration range studied (5-400 microM), studies showed the participation of a single CoA ligase in the formation of FPF-CoA, in contrast with the involvement of several isozymes with different affinities, that has been found with ibuprofen (IPF). The Km for the reaction was dependent upon the presence of non-ionic detergent, a concentration of 0.05% Triton X-100 reducing the Km from 397 to 20 microM although the detergent had no effect on Vmax. The microsomal long-chain fatty acid CoA ligase was markedly enantioselective towards (-)-R-FPF and the formation of (-)-R-FP-CoA was inhibited by both the (+)-S enantiomer and palmitic acid.

Coenzyme A esters of 2-aryloxyphenoxypropionate herbicides and 2-arylpropionate antiinflammatory drugs are potent and stereoselective inhibitors of rat liver acetyl-CoA carboxylase

The CoA esters of diclofop, haloxyfop and fluazifop are up to 425-fold more potent than the corresponding unconjugated herbicides as inhibitors of rat liver acetyl-CoA carboxylase (EC 6.4.1.2); the most potent inhibitor is (R)-fluazifopyl-CoA2 (Ki = 0.03 microM). The binding site is stereoselective for (R)-diclofop, the herbicidally active enantiomer, and for (R)-diclofopyl-CoA. The CoA esters of the antiinflammatory drugs ibuprofen and fenoprofen also strongly inhibit this carboxylase. (S)-Ibuprofenyl-CoA (Ki = 0.7 microM), the CoA ester of the enantiomer with antiinflammatory activity, is 15-fold more potent as an inhibitor than (R)-ibuprofenyl-CoA. These results suggest that some of the biological effects of these herbicides and antiinflammatory drugs in animals may be due to the inhibition of acetyl-CoA carboxylase by their acyl-CoA derivatives.