Preparation of two-drug composite microparticles to improve the dissolution of insoluble drug in water for use with a 4-fluid nozzle spray drier

In this study, we used a novel 4-fluid nozzle spray drier to prepare composite microparticles of a water-insoluble drug, flurbiprofen (FP), and a water-soluble drug, sodium salicylate (SS), for the purpose of improving the water solubility of FP. An ethanol solution of FP and an aqueous SS solution were simultaneously introduced through different liquid passages in the 4-fluid nozzle spray drier and then spray-dried. Quantitative elemental analysis suggested that the FP/SS ratio in each composite microparticle was nearly the same as the formulation ratio. We also found that SS and FP exist in a low crystallinity state in the composite particles. Release of FP from dissolved composite microparticles was markedly improved because of an increase in the effective surface area following rapid dissolution of SS. This study shows that it is possible to prepare FP-SS composite microparticles using a 4-fluid nozzle spray drier in single process and that this can improve the ability of FP to dissolve in water.

Docking studies on NSAID/COX-2 isozyme complexes using contact statistics analysis

The selective inhibition of COX-2 isozymes should lead to a new generation of NSAIDs with significantly reduced side effects; e.g. celecoxib (Celebrex) and rofecoxib (Vioxx). To obtain inhibitors with higher selectivity it has become essential to gain additional insight into the details of the interactions between COX isozymes-and NSAIDs. Although X-ray structures of COX-2 complexed with a small number of ligands are available, experimental data are missing for two well-known selective COX-2 inhibitors (rofecoxib and nimesulide) and docking results reported are controversial. We use a combination of a traditional docking procedure with a new computational tool (Contact Statistics analysis) that identifies the best orientation among a number of solutions to shed some light on this topic.

Solid lipid nanoparticles bearing flurbiprofen for transdermal delivery

Topical application of the drugs at the pathological sites offer potential advantages of delivering the drug directly to the site of action and thus producing high tissue concentrations of the drug. The solid lipid nanoparticles (SLN) bearing flurbiprofen were prepared by microemulsion method by dispersing o/w microemulsion in a cold aqueous surfactant medium under mechanical stirring. The SLN gel was prepared by adding SLN dispersion to polyacrylamide gel prepared by using polyacrylamide (0.5%), glycerol (10%), and water (69.5%). Shape and surface morphology was determined by scanning electron microscopy that revealed fairly spherical shape of the formulation. Percent drug entrapment was higher in SLN dispersion in comparison to SLN gel formulations. In vitro drug release, determined using cellophane membrane, showed that SLN dispersion exhibited higher drug release compared with SLN gel formulations. Both the SLN dispersion and SLN-gel formulation possessed a sustained drug release over a 24-hr period, but this sustained effect was more pronounced with SLN-gel formulations. The percent inhibition of edema after 8 hr was 55.51 +/- 0.26% in case of SLN-T4-gel, whereas flurbiprofen and SLN-T4 dispersion exhibited 28.81 +/- 0.46 and 31.89 +/- 0.82 inhibition of edema. The SLN-T4-gel not only decreased the inflammation to larger magnitude, but also sustained its effect.

Preparation and in vitro characterization of a semi-solid dispersion of flurbiprofen with Gelucire 44/14 and Labrasol

Flurbiprofen is characterized by low solubility in water and has been implicated in causing gastro intestinal ulceration. The purpose of this study was to increase the dissolution characteristics of flurbiprofen by preparing a semi-solid dispersion with Gelucire 44/14 and Labrasol (F1) in hard gelatin capsules. The results were evaluated by comparing several in vitro parameters with powdered drug filled into hard gelatin capsules. The in vitro dissolution testing of the dosage forms was performed in different media (simulated gastric fluid, pH 1.2; citrate buffer pH 4.5; phosphate buffers pH 6.8 and 7.2, and water). Characterization of semi-solid dispersions and physical mixtures was performed using Fourier transform-infrared spectroscopy (FT-IR), Differential scanning calorimetry (DSC), particle size analysis and turbidity measurement. The results suggest that all semi-solid dispersions of flurbiprofen showed a remarkable improvement in the rate and extent of drug dissolution. The dissolution of F1 exhibited significant improvement in all dissolution media at different pH. The dissolution of flurbiprofen within 30 min in pH 1.2 was (55%), in pH 4.5 67%, pH 6.8 96%, pH 7.2 98% and in water 88%. FT-IR indicated no strong drug: excipient interactions, and DSC studies indicated a loss of crystalline nature of the drug. The particle size analysis revealed an average size diameter from 194 to 278 nm. Therefore, a semi-solid dispersion of flurbiprofen with Gelucire and Labrasol may have the potential of improved bioavailability because of the enhanced in vitro properties.

Pharmacokinetics and synovial fluid concentrations of flurbiprofen enantiomers in horses: chiral inversion

Flurbirpofen (FBP), a member of the 2-aryl propionate nonsteroidal anti-inflammatory drug class, has potent anti-inflammatory and analgesic properties. The commercial preparation is a racemic mixture of the R(-) and S(+) enantiomers of FBP. In this study, R(-) and S(+) FBP were used to investigate the metabolic chiral inversion. Each enantiomer was administered separately (0.25 mg/kg) and in a racemic mixture (0.5 mg/kg) intravenously to horses. Plasma and synovial concentration of each enantiomer was determined and the disposition of each was analyzed. After intravenous administration of R(-) FBP and S(+) FBP to horses no chiral inversion was detected. After the administration of the FBP racemate and individual enantiomers no differences were observed between pharmacokinetic parameters [t(1/2beta) (h), Cl (L/h.kg), AUC (microg.h/mL), Vss (L/kg) and MRT (h)] for R(-) and S(+) FBF. Synovial fluid concentrations of both FBP enantiomers were lower than plasma concentrations and no stereoselective differences were detected. These data indicate that the disposition of FBF in horses is not enantioselective and demonstrate a difference in the pharmacokinetic behavior of the enantiomers as compared with other 2-aryl-propionic acids, such as carprofen, ketoprofen and vedaprofen in the horse.

Activity of flurbiprofen and chemically related anti-inflammatory drugs in models of Alzheimer's disease

Currently, there is an intense debate on the potential use of nonsteroidal anti-inflammatory drugs (NSAIDs) in Alzheimer's disease (AD). NSAIDs are among the most widely prescribed drugs for the treatment of pain, fever, and inflammation. Their effects are largely attributed to the inhibition of the enzymatic activity of cyclooxygenase (COX)-1 and -2. The apparent activity of this class of drugs stems from one critical pathological process underlying AD and other neurodegenerative disorders, i.e., the presence of chronic neuroinflammation. In fact, prolonged use of NSAIDs is associated with reduced risk of AD. Besides COX inhibition, additional mechanisms could contribute to the potential activity of NSAIDs in AD. For example, several studies show that only a few selected NSAIDs also affect beta-amyloid (Abeta) deposition and metabolism. Among the Abeta-effective NSAIDs, flurbiprofen raised particular interest because of its multiple actions on key AD hallmarks. Studies in cell lines and animal models have shown that flurbiprofen racemate, its R-enantiomer and its nitric oxide (NO)-releasing derivatives, HCT 1026 and NCX 2216, are effective on AD amyloid pathology. Moreover, HCT 1026 and NCX 2216 differentially influence the cellular component of neuroinflammation (i.e., microglia activation) in some experimental settings, i.e., HCT 1026 inhibits the activation of microglia, while NCX 2216 can either enhance or inhibit microglial activation, depending upon the experimental conditions. It is still unclear which effects on microglia will prove most beneficial. Ultimately, clinical studies in AD patients will provide the best information as to whether selected NSAIDs will improve this devastating disease.

Reversal of elution order for profen acid enantiomers in packed-column SFC on Chiralpak AD

Enantiomeric separations of four 2-substituted propionic acid drugs have been studied using packed-column supercritical fluid chromatography (SFC) with amylose tris(3,5-dimethylphenylcarbamate) coated on silica as support (Chiralpak AD). Under standard conditions (i.e., flow rate, 1.5 ml/min; column temperature, 30 degrees C; back-pressure, 150 bar), the order of elution could be reversed when the polar alcohol modifier methanol in carbon dioxide was replaced by 2-propanol for ibuprofen, ketoprofen, and naproxen. For flurbiprofen, with the highest selectivity factor, no reversal was observed, although selectivity was reduced significantly with higher alcohols. Naproxen and flurbiprofen were also investigated with 2-butanol and 2-pentanol. The former showed reversal of elution order but not the latter. For higher alcohol modifiers, including 2-propanol, the peak symmetry was poor but could be improved by addition of citric acid in the alcohol modifier. These results stress the importance to investigate enantiomer elution order during the development of enantioselective methods and when chromatographic conditions are optimized. Preliminary experiments with column temperatures over the range of -15 to 45 degrees C revealed that, in a few cases, reversal took place with a change in temperature only.

Effect of Pore Size of FSM-16 on the Entrapment of Flurbiprofen in Mesoporous Structures

The interaction between FSM-16 and flurbiprofen (FBP) in the mesopores of FSM-16 was investigated by using three types of FSM-16 with different pore diameters, i.e., FSM-16(Oc), FSM-16(Do) and FSM-16(Doc) (pore diameters 16.0, 21.6, 45.0 A, respectively). Solid dispersions of 30% FBP-70% FSM-16 were prepared by solvent evaporation and sealed-heating of the physical mixture at 100 degrees C for 6 h. Changes in the molecular state of FBP were investigated using powder X-ray diffractometry, thermal analysis and FT-IR spectroscopy. The changes in pore diameter and specific surface area of FSM-16 systems were investigated by small angle X-ray scattering and nitrogen gas adsorption. Powder X-ray diffractometry and thermal analysis revealed that FBP was adsorbed onto the mesopores of FSM-16(Do) and FSM-16(Doc), leading to an amorphous state, while no change was observed for FSM-16(Oc). Fourier-transformed IR spectroscopy showed a hydrogen bond interaction between the carbonyl groups of FBP and the silanol groups of FSM-16. The pore diameter and specific surface area of FSM-16 in solid dispersions decreased due to the adsorption of FBP. Improved dissolution of FBP from solid dispersions prepared by the evaporation and the sealed-heating methods was observed in comparison with FBP crystals.

Enantioseparation of flurbiprofen and ketoprofen in patches and in urine excretions by achiral gas chromatography

The enantiomeric composition tests on flurbiprofen and ketoprofen present in patch products and in urine excretions following patch applications were performed as diastereomeric (R)-(+)-1-phenylethylamides by achiral gas chromatography and by gas chromatography-mass spectrometry in selected ion monitoring mode. The method for determination of (R)- and (S)-enantiomers in the range from 0.1 to 5.0 microg was linear (r > or = 0.9996) with acceptable precision (% RSD < or = 5.2) and accuracy (% RE = 0.6 approximately -2.4). The enantiomeric compositions of flurbiprofen in one patch product and of ketoprofen in five different products were identified to be racemic with relatively good precision (< or = 6.4%). The urinary excretion level of (R)-flurbiprofen was two times higher than its antipode, while the comparable excretion levels of (R)- and (S)-enantiomers for ketoprofen were observed.

Evaluation of the bioavailability of flurbiprofen and its β-cyclodextrin inclusion complex in four different doses upon oral administration to rats

The dissolution profiles of flurbiprofen (Flu) and its beta-cyclodextrin inclusion complex (Flu/beta-CD) in buffer solutions at various pH values were examined. The percent dissolved at 15 min for Flu and Flu/beta-CD was almost 100% at pH 6.8 and 8.0 but the dissolution rate of Flu was extremely reduced at pH 1.2 and 4.0. In these lower pH conditions, Flu/beta-CD improved the dissolution rate of Flu. The percent dissolved at 1 h for Flu/beta-CD at pH 1.2 and 4.0 were 33.4 and 41.3%, respectively, and about 10 times larger than those for Flu. The oral bioavailability of Flu from Flu or Flu/beta-CD at doses of 1, 3, 10, and 30 mg/kg (as Flu) was examined in rats. An apparent linear relationship between doses and C(max) and AUC was observed after administration of Flu and Flu/beta-CD. The Flu C(max) and AUC values at 30 mg/kg, however, were much lower than would have been predicted from doses of 1-10 mg/kg. Those of Flu/beta-CD were also lower than the predicted values, but the gap was quite small. The results suggest that the absorption of Flu in rats was saturated at 10 mg/kg, and that the enhanced dissolution rate of Flu/beta-CD increased the saturation dose to 30 mg/kg.

S- but not R-enantiomers of flurbiprofen and ibuprofen reduce human microglial and THP-1 cell neurotoxicity

The protective effects of non-steroidal anti-inflammatory drugs (NSAIDs) in Alzheimer's disease have been demonstrated in multiple epidemiological studies. It has been hypothesized that this is due to their effects on amyloid beta-peptide (Abeta) metabolism, which is independent of the NSAID stereoisoform, rather than inhibition of cyclooxygenase (COX), which is a property of S-enantiomers. We compared the neuroprotective activity of S- and R-enantiomers of flurbiprofen and ibuprofen in a standard assay where secretions from activated human THP-1 or microglial cells are toxic to neuroblastoma SH-SY5Y cells. We found S- but not R-enantiomers to be protective at low concentrations, which is consistent with a COX-dependent mechanism.

The flurbiprofen derivatives HCT1026 and HCT1027 inhibit bone resorption by a mechanism independent of COX inhibition and nitric oxide production

Prostaglandins and nitric oxide both modulate bone resorption and bone formation. We previously reported that a nitrosylated derivative of flurbiprofen, termed HCT1026, exerted inhibitory effects on osteoclastic bone resorption, which could not be reproduced by combining the parent compound with nitric oxide (NO) donors. The aim of this study was to investigate the mechanism by which HCT1026 inhibits bone resorption. We compared the effects of flurbiprofen and HCT1026 on osteoclast and osteoblast activity with those of HCT1027--an analogue of HCT1026, which lacks an NO-donating moiety. We found that HCT1026 and HCT1027 inhibited bone resorption in interleukin (IL)-1-stimulated murine osteoblast-bone marrow cocultures, with half-maximal effects (IC50) at 20 +/- 5 microM for HCT1026 and 25 +/- 6 microM for HCT1027 compared with 399 +/- 25 microM for flurbiprofen (P < 0.0001). These differences were unrelated to cyclooxygenase (COX) inhibition since HCT1026 and HCT1027 were about seven to eight times less potent than flurbiprofen at inhibiting COX-1 activity and half as potent at inhibiting COX-2 activity. Further studies showed that HCT1026 and HCT1027 activated caspase-3 in rabbit osteoclasts and promoted osteoclast apoptosis, as assessed by nuclear morphology and TUNEL assays. We conclude that HCT1026 and HCT1027 inhibit osteoclast formation and activity by a mechanism that is independent of NO production and COX inhibition. This raises the possibility that both compounds interact with a novel molecular target expressed on osteoclasts to promote apoptosis and inhibit bone resorption. This demonstrates that HCT1026 and derivatives could represent a novel class of antiresorptive drugs with therapeutic value in the treatment of bone diseases associated with accelerated bone loss due to osteoclast activation.

Calculation of cyclodextrin binding affinities: energy, entropy, and implications for drug design

The second generation Mining Minima method yields binding affinities accurate to within 0.8 kcal/mol for the associations of alpha-, beta-, and gamma-cyclodextrin with benzene, resorcinol, flurbiprofen, naproxen, and nabumetone. These calculations require hours to a day on a commodity computer. The calculations also indicate that the changes in configurational entropy upon binding oppose association by as much as 24 kcal/mol and result primarily from a narrowing of energy wells in the bound versus the free state, rather than from a drop in the number of distinct low-energy conformations on binding. Also, the configurational entropy is found to vary substantially among the bound conformations of a given cyclodextrin-guest complex. This result suggests that the configurational entropy must be accounted for to reliably rank docked conformations in both host-guest and ligand-protein complexes. In close analogy with the common experimental observation of entropy-enthalpy compensation, the computed entropy changes show a near-linear relationship with the changes in mean potential plus solvation energy.

HPLC microdetermination offlurbiprofen enantiomers in plasma with a glycopeptide-type chiral stationary phase column

A rapid and stereospecific HPLC micromethod to quantify flurbiprofen enantiomers was developed. Both flurbiprofen enantiomers and indomethacin, used as internal standard, were extracted with methylene chloride from 100 microL of acidified plasma. The resolution of the R- and S-forms was performed on a bonded vancomycin chiral stationary phase (Chirobiotic V) with 20% of tetrahydrofuran in ammonium nitrate (100 mM, pH 5) as mobile phase. Calibration curves were linear in the range 0.5-10 microg/mL for both enantiomers. A good accuracy (< or = 5%) was obtained for all quality controls, with intra-day and inter-day variation coefficients equal or less than 7.7%. Recovery of both enantiomers was found in the range 77.4-86.3%. The lower limit of quantitation was 0.25 microg/mL for both enantiomers, without interference of endogenous components. This validated micromethod has been successfully applied for quantifying R- flurbiprofen and S- flurbiprofen in rat plasma.

The structure of human cytochrome P450 2C9 complexed with flurbiprofen at 2.0-A resolution

The structure of human P450 2C9 complexed with flurbiprofen was determined to 2.0 A by x-ray crystallography. In contrast to other structurally characterized P450 2C enzymes, 2C5, 2C8, and a 2C9 chimera, the native catalytic domain of P450 2C9 differs significantly in the conformation of the helix F to helix G region and exhibits an extra turn at the N terminus of helix A. In addition, a distinct conformation of the helix B to helix C region allows Arg-108 to hydrogen bond with Asp-293 and Asn-289 on helix I and to interact directly with the carboxylate of flurbiprofen. These interactions position the substrate for regioselective oxidation in a relatively large active site cavity and are likely to account for the high catalytic efficiency exhibited by P450 2C9 for the regioselective oxidation of several anionic non-steroidal anti-inflammatory drugs. The structure provides a basis for interpretation of a number of observations regarding the substrate selectivity of P450 2C9 and the observed effects of mutations on catalysis.

The 2.0 A resolution crystal structure of prostaglandin H2 synthase-1: structural insights into an unusual peroxidase

Prostaglandin H2 synthase (EC 1.14.99.1) is an integral membrane enzyme containing a cyclooxygenase site, which is the target for the non-steroidal anti-inflammatory drugs, and a spatially distinct peroxidase site. Previous crystallographic studies of this clinically important drug target have been hindered by low resolution. We present here the 2.0 A resolution X-ray crystal structure of ovine prostaglandin H2 synthase-1 in complex with alpha-methyl-4-biphenylacetic acid, a defluorinated analog of the non-steroidal anti-inflammatory drug flurbiprofen. Detergent molecules are seen to bind to the protein's membrane-binding domain, and their positions suggest the depth to which this domain is likely to penetrate into the lipid bilayer. The relation of the enzyme's proximal heme ligand His388 to the heme iron is atypical for a peroxidase; the iron-histidine bond is unusually long and a substantial tilt angle is observed between the heme and imidazole planes. A molecule of glycerol, used as a cryoprotectant during diffraction experiments, is seen to bind in the peroxidase site, offering the first view of any ligand in this active site. Insights gained from glycerol binding may prove useful in the design of a peroxidase-specific ligand.

Manipulation of kinetic profiles in 2-aryl propionic acid cyclooxygenase inhibitors

The nonsteroidal anti-inflammatory drugs flurbiprofen and ibuprofen were modified in an attempt to alter the kinetics of inhibitor binding by COX-1. Contrary to prior predictions, a halogen substituent is not sufficient to confer slow tight-binding behavior. Conversion of the carboxylate moiety of flurbiprofen to an ester or amide abolishes slow tight-binding behavior, regardless of halogenation state.

Modeling of adhesion in tablet compression. II. Compaction studies using a compaction simulator and an instrumented tablet press

Adhesion problems are usually not identified until prolonged compression runs are studied near the end of the drug development process. During tablet manufacturing, adhesion problems encountered are usually addressed by statistically designed experiments based on experience. It would be a significant benefit for the pharmaceutical industry if adhesion problems could be identified early in drug development based on molecular considerations of the drug substance and/or prototype formulations. Drug substance-punch face interactions were reported in the first of the articles in this series, and focused on the elucidation of adhesion problems in tablet compression. It was hypothesized that the intermolecular interactions between drug molecules and the punch face was the first step (or criterion) in the adhesion process, and that the rank order of adhesion during tablet compression should correspond with the rank order of these energies of interaction. That is, the interaction between the molecular structure of the drug and the metal surface determines the primary interaction event or relative potential for adhesion, while the mechanical processes and/or lubrication effects may subsequently impact the extent of adhesion. Molecular simulations and atomic force microscopy were used to establish the rank order of the work of adhesion of a series of profen compounds. The results predicted that the relative degree of drug substance-punch face adhesion should decrease in the order of ketoprofen > ibuprofen > flurbiprofen. In this study, the authors investigated whether the rank order of the work of adhesion established on the molecular level and interparticulate level holds true in the tableting environment by measuring tablet take-off force, ejection force, and visual observation of the punch surfaces for both pure drug compacts and formulated tablets. The compaction simulator was used for pure profen compacts, while the instrumented tablet press for formulated tablets. Due to the inability to extract the adhesion force component from the total ejection force measurement, tablet ejection force was not used as a criterion to judge the adhesion behavior of the model compounds. The criteria used for judgement of punch face adhesion were tablet take-off force and visual observation of the punch faces. The rank order of adhesion for both pure drug and formulated tablets was determined to follow the order of ketoprofen > ibuprofen > flurbiprofen. The effect of run time on adhesion behavior was also investigated. Therefore, the rank order of the punch-face adhesion tendencies for the series of profen compounds was determined, and found to agree with the data from the predictive methods reported in the first article.

Bioinversion ofR-flurbiprofen toS-flurbiprofen at various dose levels in rat, mouse, and monkey

Information about the potential and extent of bioinversion of chiral drugs in laboratory animal species and humans is critical to the interpretation of preclinical pharm-tox studies with these drugs. Unlike in the dog, guinea pig, and rabbit, in humans the 2-arylpropionic acid (APA) R-flurbiprofen (R-FB) undergoes very little bioinversion to S-flurbiprofen. The primary objective of this research was to identify laboratory animal species with an R- to S-bioinversion profile similar to humans. Detailed evaluations of the pharmacokinetics parameters of R-flurbiprofen in male and female rats and mice, and male nude rats and monkeys demonstrated R- to S-bioinversion of 30% (average) in monkeys, 15-24% in mice, and approximately 4% in rats. To date, no laboratory animal species has been identified with an R-flurbiprofen bioinversion profile identical to humans. However, the rat has a bioinversion profile sufficiently similar to humans to be useful for preclinical.

In vitro release and stereoselective disposition of flurbiprofen loaded to poly(D,L-lactide-co-glycolide) nanoparticles in rats

Flurbiprofen (FL) is a chiral 2-arylpropionate used clinically as the racemate (rac-FL). This study was undertaken to investigate the influence of sustained release formulation on the pharmacokinetics of flurbiprofen enantiomers (-) -R-FL and (+)-S-FL. Therefore, a stereoselective high-performance liquid chromatographic (HPLC) method was developed and validated for the rapid, quantitative determination of (-)-R-FL and (+)-S-FL in rat plasma. Flurbiprofen-loaded poly(D,L-lactide-co-glycolide) nanoparticles (rac-FL-PLGA) were prepared by in emulsion-solvent evaporation technique. Optimum conditions for rac-FL-PLGA nanoparticle preparation were considered, and the in vitro release of rac-FL, R-FL, and S-FL were followed up to 48 h in phosphate buffer (pH 7.4). The three tested formulations revealed approximately zero-order release of either (-)-R-FL or S-FL up to 24 h with r >/= 0.97.Surprisingly, there was no significant difference between t(50%) of the three formulations (21.6 +/- 1.1 h). The stereoselective disposition of the sustained release rac-FL deliverv system was investigated in rats. There was a rapid release of R-FL, S-FL, or rac-FL followed by a slower one and C(max) values were observed after 2.5 +/- 2.5, 8.3 +/- 3.4 and 8.86 +/- 3.6 h of (-)-R-FL, (+)-S-FL, and rac-FL, respectively, after nanoparticle administration. PLGA nanoparticles increased the mean retention time (MRT) of S-FL by 2.7-fold, from 6.8 to 16.3 h, compared to rac-FL. Although the dose of rac-FL-PLGA nanoparticles was only 2.5 times higher than that of the drug in the suspension, the mean (+)-S-FL concentration after 12 h was 3.4 times higher in the case of nanoparticles than after the free form, 10.35 +/- 1.6 and 3.04 +/- 1.1 mg/l, respectively. The area under the concentration-time curve (AUC) values of (+)-S-FL and rac-FL were about 2.5-fold higher after the nanoparticles compared to suspension, while the AUC of the (-)-R-FL was about 3.5 times higher. This difference may indicate that the two enantiomers have different absorption kinetics. The present study provides evidence that the sorption of racemic flurbiprofen to PLGA nanoparticles was successful in maintaining (at least up to 12 h) elevated plasma drug concentrations of (+)-S-FL in rats. Chirality 16:119-125, 2004.

Characterisation of the lowest singlet and triplet excited states of S-flurbiprofen

The photophysical properties of S-flurbiprofen [S-2-fluoro-alpha-methyl-4-biphenylacetic acid], a nonsteroidal anti-inflammatory drug, have been examined using steady-state and time-resolved spectroscopic techniques. The energy of its first singlet excited state is 99 kcal mol(-1). The fluorescence quantum yields and lifetimes (at 300 nm) have been determined in acetonitrile, methanol, hexane and PBS; they are in the range 0.15<phi(F)< 0.33 and 0.7<tau(F)<2.0 ns. The intersystem crossing quantum yields are between 0.45 and 0.71; the lambda(max) of the T-T absorption is 360 nm, and the triplets live from 15 to 106 micros. Steady state photolysis in aqueous medium leads to S-2-hydroxy-alpha-methyl-4-biphenylacetic acid via photonucleophilic aromatic substitution, in addition to the photodecarboxylation products observed in organic solvents.

Investigation of the Release Test Method for the Topical Application of Pharmaceutical Preparations: Release Test of Cataplasm Including Nonsteroidal Anti-inflammatory Drugs Using Artificial Sweat

A simple procedure for determining the in vitro release profile of a cataplasm for use in a quality control procedure has been developed. Since the disk assembly in the USP for patch dosage forms was unsuited for use in a release test due to penetration of the dissolution medium into the cataplasm from the screw part of the device and the cataplasm swelled, new holders were designed. In the new holder, a cataplasm is held in position by sandwiching it between a stainless-steel O-ring and a silicon O-ring on the stainless steel board, 2 acrylic boards hold the O-rings and the stainless steal board, and the entire assembly is placed at the bottom of the dissolution vessel. The release profile was determined using the "Paddle over Disk" method in USP26. Furthermore, in order to prevent the swelling of the cataplasm, artificial sweat was used as the dissolution medium. The release profiles of the nine marketed brands of cataplasm containing indomethacin, ketoprofen, and flurbiprofen, respectively, were determined over a 12-h period. By adjusting the ion concentration and volume of the media, and the release surface-area of the cataplasm exposed to each medium, the procedure was found to be reproducible for in vitro release characterization of nine marketed brands. This shows that this technique can be used as a quality control tool for assuring product uniformity.

Preparation and characterization of flurbiprofen beads by melt solidification technique

A melt solidification technique has been developed to obtain sustained-release waxy beads of flurbiprofen. Low glass transition temperature (t(g)) and shear-induced crystallization of flurbiprofen made it a suitable candidate for melt solidification technique. The process involved emulsification and solidification of flurbiprofen-cetyl alcohol melt at significantly low temperature (5 degrees C). The effect of variables, namely, the amount of cetyl alcohol and the speed of agitation, was studied using 3(2)factorial design. The technique and the beads were evaluated on the basis of process and desired yield, surface topography, Fourier-transform infrared (FT-IR), differential scanning calorimetry (DSC), particle size distribution, crushing strength, and drug release. Average values for process and desired yields were 97% wt/wt and 26% wt/wt, respectively. No interaction was observed between drug and excipient. Multiple regression analysis was carried out, and response surfaces were obtained. A curvilinear relationship was observed between percentage of desired yield and the amount of cetyl alcohol. Linear decrease in crushing strength was observed with increase in the amount of cetyl alcohol. Drug released from the beads followed zero order kinetics. Burst release was shown to a greater extent in beads containing a lower amount of cetyl alcohol. Response surfaces of time required for certain percentage of drug (t(D)%) showed that after critical concentration of about 20% of cetyl alcohol (400 mg/batch), no significant release retardant effect was observed.

Different in vitro activity of flurbiprofen and its enantiomers on human articular cartilage

The 2-arylpropionic acid derivatives or 'profens' are an important group of non-steroidal anti-inflammatory drugs that have been used for the symptomatic treatment of various forms of arthritis. These compounds are chiral and the majority of them are still marketed as racemate although it is known that the (S)- form is the principal effective in the cyclooxygenase inhibition. However, recent findings suggest that certain pharmacological effect of 2-arylpropionic acids cannot be attributed exclusively to the (S)-(+) enantiomer. To obtain further insights into the pharmacological effect of profens, the present study investigated the influence of racemic and pure enantiomers of flurbiprofen on the production of nitric oxide and glycosaminoglycans, key molecules involved in cartilage destruction. The culture of human articular cartilage stimulated by interleukin-1beta (IL-1beta), which plays an important role in the degradation of cartilage, has been established, as a profit experimental model, for reproducing the mechanisms involved in the pathophysiology of arthritic diseases. Our results show that mainly (S)-(+)-flurbiprofen decreases, at therapeutically concentrations, the IL-1beta induced cartilage destruction.