Comparison of the nephroprotective effects of non-steroidal anti-inflammatory drugs on cisplatin-induced nephrotoxicity in vitro and in vivo.

Cisplatin (CDDP) is an anticancer drug, often used in the treatment of several types of cancers. CDDP-induced nephrotoxicity (CIN) is one of the most severe adverse events associated with the use of CDDP. It has been suggested that the co-administration of non-steroidal anti-inflammatory drugs (NSAIDs) is a risk factor for CIN. However, the specific NSAIDs that affect CIN and the precise mechanisms underlying this interaction remain unclear. Hence, we aimed to evaluate the effect of NSAIDs on CDDP-induced cytotoxicity in vitro and confirmed the results in vivo. Using the epithelioid clone of the normal rat kidney cells (NRK-52E cells), we assessed the effects of 17 NSAIDs on CDDP-induced cytotoxicity all at once using the MTT assay. Furthermore, we evaluated two NSAIDs, which significantly attenuated or enhanced CDDP-induced cytotoxicity, in vivo. Wistar rats were treated with CDDP (5 mg/kg, i.p., day 1) and NSAIDs (p.o., day 1-4), and the kidneys were excised on day 5. Our results demonstrated that several NSAIDs attenuated, while others enhanced CDDP-induced cytotoxicity. Celecoxib significantly attenuated and flurbiprofen markedly enhanced cell dysfunction by CDDP. These results were reproduced in vivo as celecoxib decreased and flurbiprofen increased the expression of kidney injury molecule 1 (Kim-1) mRNA, a sensitive kidney injury marker, compared to the CDDP group. Moreover, celecoxib increased the antioxidant and autophagy markers quantified by qPCR in vitro and prevented a decrease in body weight induced by CDDP in vivo. In conclusion, we revealed that celecoxib significantly attenuated CIN in vitro and in vivo.

In vitro cytogenetic evaluation of the particular combination of flurbiprofen and roxithromycin.

Flurbiprofen (FLB) (anti-inflammatory and analgesic drug) and roxithromycin (RXM) (antibiotic) were widely used in world wide. This study deals with investigation of genotoxicity, cytotoxicity, and oxidative stress effects of a particular combination of these drugs in human cultured lymphocytes. Also, DNA damaging-protective effects of combination of these drugs were analyzed on plasmid DNA. Human lymphocytes were treated with different concentrations (FLB + RXM; 10 µg/mL + 25 µg/mL, 15 µg/mL + 50 µg/mL, and 20 µg/mL + 100 µg/mL) of the drugs following by study of their genotoxic and cytotoxic effects by analysis of cytokinesis-block micronucleus test and nuclear division index, respectively. The effect of the combination in aspect of anti-oxidative and DNA damaging activity was evaluated on Pet-22b plasmid. According to our results, the combination of FLB and RXM did not show a notable genotoxic effect on cells. Although each of the substances had been shown as a cytotoxic agent by previous researchers, in this research, the combination of these drugs did not exhibit any adverse effect on cell division. FLB had DNA protection effect against H2O2 while in combination with RXM had not the same effect on the plasmid.

Assessment of in vitro genotoxic and cytotoxic effects of flurbiprofen on human cultured lymphocytes.

Flurbiprofen is non-steroidal anti-inflammatory drug which is commonly used for its analgesic, antipyretic, and anti-inflammatory effects. The purpose of the study was to explore the genotoxic and cytotoxic effects of flurbiprofen in human cultured lymphocytes by sister chromatid exchange, chromosome aberration, and cytokinesis-blocked micronucleus tests. 10, 20, 30, and 40 µg/mL concentrations of flurbiprofen (solvent is DMSO) were used to treatment of human cultured lymphocytes at two different treatment periods (24 and 48 h). Flurbiprofen had no significant genotoxic effect in any of these tests. But exposing to flurbiprofen for 24 and 48 h led to significant decrease on proliferation index, mitotic index, and nuclear division index (NDI). Also, all decreases were concentration-dependent (except NDI at 24 h treatment period). Consequently, the findings of this research showed that flurbiprofen had cytotoxic effects in human blood lymphocytes.

Cyclosporin A-sensitive cytotoxicity of flurbiprofen non-stereoselectively mediated by cytochrome P450 metabolism in three-dimensional cultured rat hepatocytes.

OBJECTIVES: 2-Arylpropionic acid (profen) drugs are associated with severe hepatotoxicity; however, risk factors are still poorly understood. Acyl-coenzyme A (acyl-CoA) thioesters of profen drugs play a more important role in the covalent binding to rat hepatocyte proteins than the respective acyl-glucuronides. Therefore, we examined whether acyl-glucuronides, acyl-CoA thioesters and oxidative metabolites of profen drugs stereoselectively participated in liver damage. METHODS: Cytotoxicity was determined by measuring lactate dehydrogenase (LDH) leakage from three-dimensional cultured rat hepatocytes. KEY FINDINGS: LDH leakage was not induced by R-2-phenylpropionic acid and R-ibuprofen greatly forming acyl-CoA thioesters. S-Naproxen metabolized mainly by Uridine 5'-diphosphate (UDP)-glucuronosyl-transferase did not enhance LDH leakage. However, flurbiprofen (FLP) induced LDH leakage. A selective cytochrome P450 (CYP) 2C11 inhibitor suppressed 40-50% of the R-FLP and S-FLP-induced cytotoxicity. Borneol non-stereoselectively accelerated the FLP-induced cytotoxicity. The R-FLP-induced cytotoxicity decreased intracellular adenosine triphosphate (ATP) levels to 50% of untreated hepatocytes. An inhibitor of mitochondrial permeability transition pore, cyclosporin A (Cys A), rescued ATP levels and LDH leakage back to control levels. CONCLUSION: The reactive acyl-CoA thioesters and acyl-glucuronides were not associated with liver damage, denying one of the leading hypotheses. CYP metabolism of FLP non-stereoselectively participated in Cys A-sensitive cytotoxicity, suggesting mitochondrial injury.

Investigation of flurbiprofen genotoxicity and cytotoxicity in rat bone marrow cells.

This study was performed to investigate cytogenetic effects of NSAID flurbiprofen which was used as active ingredient in some analgesic, antipyretic and anti-inflammatory drugs. Genotoxic effect of flurbiprofen was investigated using in vivo chromosome aberration (CA) test and random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) test. Also, oxidative stress potential of flurbiprofen was determined by measuring total oxidant and antioxidant level which occurred with flurbiprofen treatment in rat peripheral blood. For these purposes, rats were treated with three concentrations of flurbiprofen (29.25, 58.50 and 117 mg/kg, body weight) in single dose at two different treatment periods (12 and 24 h). According to the results, flurbiprofen did not affect chromosome aberrations in rat bone marrow cells with CA test. In RAPD-PCR test, polymorphic bands were unaffected. Also, test substance did not change total oxidant and antioxidant status (except for 58.50 and 117 mg/kg, 12 h) and therefore it did not lead to significant increase on oxidative stress (again except 58.50 and 117 mg/kg, 12 h). However, flurbiprofen reduced to mitotic indexes and these reductions were dose-dependent for 12 h treatment. In summary, flurbiprofen did not show significant genotoxic effect. But it caused cytotoxicity in rat bone marrow cells.

Transglycosylated rutin-specific non-surface-active nanostructure affects absorption enhancement of flurbiprofen.

Transglycosylated rutin (Rutin-G), a newly developed transglycosylated food additive, was used as a novel excipient for improving the dissolution and absorption properties of flurbiprofen. No surface activity was found up to 100mg/mL of Rutin-G concentration. No cytotoxicity to Caco-2 cells was observed even at a high level of 100mg/mL Rutin-G solution. (1)H NMR study with concentration variation revealed that Rutin-G formed small aggregates in water, with the aggregation number of Rutin-G above the critical aggregation concentration of about 5.0mg/mL being 4. Structural analyses by small-angle X-ray scattering determined the aggregate to be several nanometers in maximum length. A solubility test of flurbiprofen in the presence of Rutin-G showed that the amount of dissolved flurbiprofen increased in proportion to the amount of Rutin-G loaded. This finding indicated a stoichiometric relationship between flurbiprofen and Rutin-G. The spray-dried particles of flurbiprofen/Rutin-G showed a significantly higher dissolution rate and greater absorption profile compared with the commercial flurbiprofen powder. Taken together, the results indicate the potential application of Rutin-G in the formation of a novel nanostructure of drug/transglycosylated material.

Potential use of nanostructured lipid carriers for topical delivery of flurbiprofen.

The potential use of nanostructured lipid carriers (NLC) composed of a fatty acid [stearic acid (SA)] or a triglyceride (glyceryl behenate) as solid lipids, and a mixture of medium chain triglycerides and castor oil as liquid lipids, for skin administration of flurbiprofen (FB), has been explored. Two different optimized NLC formulations (FB-SANLC based on SA vs. FB-C888NLC based on glyceryl behenate), with respect to the morphometrical properties (particle size and polydispersity index) and the entrapment efficiency, were used in this study. The ex vivo permeation profiles of FB-C888NLC, FB-SANLC and conventional FB solution were evaluated using human skin. An improved FB permeation was observed when the drug was delivered by skin application of FB-C888NLC, attributed to the particle size and matrix crystallinity. The differential scanning calorimetry and X-ray diffraction studies suggested major polymorphic transitions in the lipid matrix of FB-C888NLC. A good correlation between polymorphic transitions and increased drug permeation was observed. However, both NLC dispersions showed a penetration-enhancing ratio (ER) higher than conventional FB solution. The in vitro and in vivo irritancy and local tolerability were assessed by running, respectively, the SKINTEX™ and Draize test. Both FB-C888NLC and FB-SANLC were classified as nonirritant.

Novel vehicle based on cubosomes for ophthalmic delivery of flurbiprofen with low irritancy and high bioavailability.

AIM: To develop a novel vehicle based on cubosomes as an ophthalmic drug delivery system for flurbiprofen (FB) to reduce ocular irritancy and improve bioavailability. METHODS: FB-loaded cubosomes were prepared using hot and high-pressure homogenization. Cubosomes were then characterized by particle size, zeta potential, encapsulation efficiency, particle morphology, inner cubic structure and in vitro release. Corneal permeation was evaluated using modified Franz-type cells. Ocular irritation was then evaluated using both the Draize method and histological examination. The ocular pharmacokinetics of FB was determined using microdialysis. RESULTS: The particle size of each cubosome formulation was about 150 nm. A bicontinuous cubic phase of cubic P-type was determined using cryo-transmission electron microscopy (cryo-TEM) observation and small angle X-ray scattering (SAXS) analysis. In vitro corneal permeation study revealed that FB formulated in cubosomes exhibited 2.5-fold (F1) and 2.0-fold (F2) increase in P(app) compared with FB PBS. In the ocular irritation test, irritation scores for each group were less than 2, indicating that all formulations exhibited excellent ocular tolerance. Histological examination revealed that neither the structure nor the integrity of the cornea was visibly affected after incubation with FB cubosomes. The AUC of FB administered as FB cubosome F2 was 486.36+/-38.93 ng.mL(-1).min.microg(-1), which was significantly higher than that of FB Na eye drops (P<0.01). Compared with FB Na eye drops, the T(max) of FB cubosome F2 was about 1.6-fold higher and the MRT was also significantly longer (P<0.001). CONCLUSION: This novel low-irritant vehicle based on cubosomes might be a promising system for effective ocular drug delivery.

Design and ocular tolerance of flurbiprofen loaded ultrasound-engineered NLC.

Packaging small drug molecules, such as non-steroidal anti-inflammatory drugs (NSAIDs) into nanoparticulate systems has been reported as a promising approach to improve the drug's bioavailability, biocompatibility and safety profiles. In the last 20 years, lipid nanoparticles (lipid dispersions) entered the nanoparticulate library as novel carrier systems due to their great potential as an alternative to other systems such as polymeric nanoparticles and liposomes for several administration routes. For ocular instillation nanoparticulate carriers are required to have a low mean particle size, with the lowest polydispersity as possible. The purpose of this work was to study the combined influence of 2-level, 4-factor variables on the formulation of flurbiprofen (FB), a lipophilic NSAID, in lipid carriers currently named as nanostructured lipid carriers (NLC). NLC were produced with stearic acid (SA) and castor oil (CO) stabilized by Tween® 80 (non-ionic surfactant) in aqueous dispersion. A 2(4) full factorial design based on 4 independent variables was used to plan the experiments, namely, the percentage of SA with regard to the total lipid, the FB concentration, the stabilizer concentration, and the storage conditions (i.e., storage temperature). The effects of these parameters on the mean particle size, polydispersity index (PI) and zeta potential (ZP) were investigated as dependent variables. The optimization process was achieved and the best formulation corresponded to the NLC formulation composed of 0.05 (wt%) FB, 1.6 (wt%) Tween® 80 and a 50:50 ratio of SA to CO, with an average diameter of 288 nm, PI 0.245 of and ZP of -29 mV. This factorial design study has proven to be a useful tool in optimizing FB-loaded NLC formulations. Stability of the optimized NLC was predicted using a TurbiScanLab® and the ocular tolerance was assessed in vitro and in vivo by the Eytex® and Draize test, respectively. The developed systems were shown physico-chemically stable with high tolerance for eye instillation.

Influence of prolonged exposure of a short half life non-steroidal anti-inflammatory drugs on gastrointestinal safety.

AIMS: To test the influence of frequent concentration peaking, as occurs in multiple-dosing of non-steroidal anti-inflammatory drugs (NSAIDs) with short t (1/2), and duration of therapy of NSAIDs on gastrointestinal permeability. METHODOLOGY: 2.5 mg/(kg 12 h) flurbiprofen was administered as repeated oral and interperitoneal (i.p) doses or as i.p. osmotic pump (once implanted to mimic long t(1/2)) for 7 days to healthy rats. Urinary excretion of (51)Cr-EDTA (days 0, 1, 4 and 7 during all regimens) and sucrose (days 0, 1 and 7 for i.p. doses) were measured as markers of gastroduodenal and intestinal permeability, respectively. RESULTS: Both i.p. regimens elevated (51)Cr-EDTA permeability suggestive of a systemic effect. There was no significant difference between the i.p regimens in (51)Cr-EDTA permeability. The first day (51)Cr-EDTA permeability was significantly higher for the oral than for the i.p. doses suggestive of a topcal effect. The effect became less potent with time despite continuous dosing indicating adaptation for both topical and systemic effects. None of the i.p. regimen altered sucrose permeability. CONCLUSION: NSAID's potency to increase permeability reduces with time despite continuous dosing. Topical effect following oral dosing, and not the frequent peaking differentiates regimens from each other in elevating (51)Cr-EDTA permeability. The repeated dosing rather than the magnitude of t(1/2) may influence the gut safety profile of NSAIDs.

Intravitreal toxicity of ketorolac tris salt and flurbiprofen.

BACKGROUND AND OBJECTIVE: To determine the retinal toxicity of intravitreal ketorolac tris salt and flurbiprofen. MATERIALS AND METHODS: Thirty-two New Zealand rabbits were injected intravitreally with 125, 250, or 500 microg or 1 mg of ketorolac tris salt or flurbiprofen in one eye and 8 fellow eyes were injected with 5% dextrose as a control. All animals underwent indirect ophthalmoscopy and slit-lamp biomicroscopy before injection and on days 1, 7, and 14 after the intravitreal injection. Electroretinography was performed on all animals before injection and on day 14 after the injection before the animals were killed. The enucleated eyes were prepared for histology. RESULTS: Clinical examination, electroretinography results, and histological evaluation demonstrated no signs of retinal toxicity for either drug at any dose. CONCLUSIONS: Intravitreal doses up to 1 mg of ketorolac tris salt and 1 mg of flurbiprofen did not cause retinal toxicity in the rabbit eye.

Optimizing delivery of flurbiprofen to the colon using a targeted prodrug approach.

The carboxylic group responsible for the gastric side-effects of the propionic acid derivative, flurbiprofen, was masked temporarily to overcome these side-effects and to accomplish colon-specific delivery of the drug. An amide prodrug (FLU-GLY) was synthesized by coupling flurbiprofen with L-glycine. Confirmation and characterization of the structure of the synthesized prodrug included elemental analysis, Fourier transform (FT)-IR, FT-NMR, mass (FAB) spectroscopy, and determinations of R(f), R(t) and R(M) values, respectively. Aqueous solubility and lipophilicity (logP) value were determined at pH 1.2, 4.0, 6.8 and 7.4. In-vitro reversion of FLU-GLY to flurbiprofen was measured at different pHs and in a simulated colonic environment. Acute toxicity and ulceration potential were evaluated in-vivo in albino rats. Pre-formulation studies showed increased hydrophilicity but a non-significant increase in lipophilicity of the prodrug. In-vitro reversion studies suggested that the prodrug remained intact until colonic pH was attained, when the colonic microfloral enzymes (amidase) hydrolysed the FLU-GLY amide linkage, releasing the free drug. In-vivo evaluation indicated that the prodrug was much less toxic and had less ulcerogenic activity than the parent drug. Selective delivery of drugs to the colon can be useful in terms of reducing the dose administered and reducing undesirable side-effects.

Drug evaluation: (R)-flurbiprofen--an enantiomer of flurbiprofen for the treatment of Alzheimer's disease.

(R)-flurbiprofen, the R-enantiomer of racemic flurbiprofen, is undergoing development by Myriad Genetics Inc, under license from Encore Pharmaceuticals Inc, for the potential treatment of Alzheimer's disease (AD). Devoid of any direct cyclooxygenase inhibition, which is associated with the more toxic S-enantiomer of flurbiprofen, (R)-flurbiprofen appears to modulate gamma-secretase, the enzyme that cleaves the C-terminal portion of the malignant Abeta(1-42) peptide out of amyloid precursor protein. In murine models of AD, (R)-flurbiprofen lowered brain levels of Abeta(1-42), and chronic dosing reduced brain amyloid pathology and prevented defects in learning and memory. In a phase II clinical trial in AD, (R)-flurbiprofen was determined to be most effective in a subset of patients who had high blood concentrations of the drug (> 75 microg/ml). These patients demonstrated a benefit in cognitive and behavioral performance that ranged from 36 to 48%, and statistical significance was achieved for two out of three trial endpoints. Compared with placebo, (R)-flurbiprofen also significantly reduced the incidence of psychiatric problems and the average time to a first psychiatric incidence. (R)-flurbiprofen has been generally well tolerated at high doses in clinical trials. Two pivotal phase III clinical trials in AD are underway in more than 2400 patients. The compound had also been under development for the treatment of prostate cancer; however, this indication was discontinued after disappointing phase IIa trial results.

Study on the mechanism of photosensitive dermatitis caused by ketoprofen in the guinea pig.

To investigate the mechanism on photosensitive dermatitis caused by ketoprofen (KP) in humans, the following experiments were performed by topical application on guinea pigs. The phototoxicity study involving treatment with 10% solution of KP, its enantiomers (R-KP and S-KP), loxoprofen, and flurbiprofen revealed no phototoxic reactions. In the photoallergenicity study, KP and its enantiomers (0.5-2% solution) induced skin reaction at all dosages; however, loxoprofen and flurbiprofen (1-5% solution) did not induce such a photoallergenic reaction. These results suggest that the chemical structure of the benzophenone chromophore in KP would be one of the important factors for induction of the photoallergy since both loxoprofen and flurbiprofen do not possess this structure and hence lack photoallergenic potential. Furthermore, to assess time profiles of KP concentration in the skin and plasma, guinea pigs received a repeated topical application of R-KP and S-KP at a dosage of 40 mg/kg over a period of 3 days. Plasma KP concentrations were extremely low as compared to skin KP concentrations and were not detected at 72 h after the final dosing. At 24 h after the final dosing, KP concentrations in the skin with R-KP and S-KP treatment were 187.4 and 254.7 microg/g, respectively, and their half-lives were 80.5 and 84.4 h, respectively. KP concentrations at 336 h after final dosing were 11.3 microg/g for R-KP and 15.7 microg/g for S-KP treatment. The acylglycerol-combined KP concentrations at 336 h were 2% or less as compared to KP concentrations with R-KP and S-KP treatment. There were no differences in KP concentrations in the skin between R-KP and S-KP and in combined KP concentrations between the enantiomers. The present study indicates that photosensitive dermatitis after topical application of KP in humans, caused by photoallergenicity and not phototoxicity, can be reproduced in the animal testing, and suggests that the skin reaction may be caused by the long period of retention of KP in the skin.

Flurbiprofen-loaded acrylate polymer nanosuspensions for ophthalmic application.

Polymeric nanoparticle suspensions were prepared from Eudragit RS100R and RL100R polymer resins and loaded with flurbiprofen (FLU), with the aim at improving the availability of the drug at an intra-ocular level for the prevention of the myosis induced during extracapsular cataract surgery. Nanosuspensions were prepared by a quasi-emulsion solvent diffusion technique using different formulation parameters (drug-to-polymer ratio, initial polymer concentration, agitation speed, etc.). The resulting nanoparticles showed mean sizes around 100 nm and a fixed positive charge (zeta-potential around +40/+60 mV). Stability tests after mid-time storage (4 degrees C or room temperature) or freeze-drying were carried out to optimise a possible final pharmaceutical preparation. In vitro, dissolution tests showed a controlled release profile of FLU from the nanoparticles. In vivo anti-inflammatory efficacy was assessed in the rabbit eye after induction of an ocular trauma (paracentesis). FLU-loaded nanosuspensions did not show toxicity on ocular tissues. Moreover, an inhibition of the miotic response to the surgical trauma comparable to a control eye-drop formulation was obtained, even though an actual lower concentration of free drug in the conjunctival sac was achieved from the nanoparticle system. Drug levels in the aqueous humour were also higher after application of the nanosuspensions.

Estimation of acute flurbiprofen and ketoprofen toxicity in rat gastric mucosa at therapy-relevant doses.

OBJECTIVE: Since assessment of the acute gastrotoxicity of nonsteroidal antiinflammatory drugs (NSAIDs) in rats requires high doses of the drugs, we sought to establish an experimental model with which this adverse NSAID effect can be estimated at therapy-relevant doses. METHODS: The study was performed with racemic flurbiprofen-trometamol (R/S-FBP), its pure enantiomers S-FBP and R-FBP, and racemic ketoprofen-trometamol (R/S-KP). Two hours after administration of FBP or KP to Sprague-Dawley rats, HCl (0.5 M, 10 ml/kg) was given intragastrically (IG), and the haemorrhagic lesion area in the gastric mucosa quantified 1 h post-HCI. RESULTS: FBP amplified gastric acid injury in a dose-related manner, the rank order of potency being S-FBP > R/S-FBP >> R-FBP. While less than 1 micromol/kg S-FBP and R/S-FBP aggravated acid injury, doses up to 50 micromol/kg failed to cause appreciable damage without subsequent HCl challenge. Similar observations were made with R/S-KP which at doses of > or = 1 micromol/kg aggravated gastric acid injury. There was no significant difference in the gastrotoxicity of FBP when the drug was administered subcutaneously or IG, whereas subcutaneously injected R/S-KP was slightly more toxic than IG R/S-KP. CONCLUSIONS: These data show that FBP- and KP-induced amplification of acid injury in the rat gastric mucosa is a sensitive assay whereby, with single drug dosing, the gastrotoxic potential of these and other NSAIDs may be estimated at therapy-relevant doses that in humans threaten mucosal integrity only following chronic use.

Stereoselective and substrate-dependent inhibition of hepatic mitochondria beta-oxidation and oxidative phosphorylation by the non-steroidal anti-inflammatory drugs ibuprofen, flurbiprofen, and ketorolac.

Non-steroidal anti-inflammatory drugs (NSAIDs) cause a range of adverse effects, some of which have been associated with perturbances of lipid metabolic pathways. Previous data demonstrating stereoselective formation of the CoA thioester of R-ibuprofen in particular were suggestive of possible stereoselective effects on lipid metabolism. Our aim was to characterise the relative stereoselectivity of the effects of ibuprofen, flurbiprofen, and ketorolac (0.01-1.0 mM) on both the beta-oxidation of palmitate and oxidative phosphorylation in rat hepatic mitochondria as a means of dissecting prostaglandin related from non-prostaglandin-related events. Beta-oxidation was inhibited stereoselectively by R-ibuprofen (P = 0.015), non-stereoselectively by R- and S-flurbiprofen (P = 0.002 and P = 0.004, respectively), and was essentially unaffected by either enantiomer of ketorolac. At 0.25 mM, inhibition by R-ibuprofen and both flurbiprofen enantiomers was partially reversed by increasing CoA concentrations (0-200 microM). Mitochondrial respiration was moderately inhibited by both enantiomers of ibuprofen and flurbiprofen (P < 0.01), but only by high concentrations (> or = 1 mM) of the enantiomers of ketorolac (P < 0.01). Uncoupling of oxidative phosphorylation measured as stimulation of State 4 respiration contributed to these effects. The data support interactions involving both stereoselective CoA-dependent and non-CoA-dependent mechanisms. The plasma drug concentrations required to achieve these effects are not likely to be attained in the majority of patients, although these concentrations are achievable in the gastrointestinal tract and may contribute to the well-known spectrum of adverse effects in this organ. Some patients do experience systemic adverse events which may be mediated by these mechanisms.

Role of tumour necrosis factor-alpha and inducible nitric oxide synthase in the prevention of nitro-flurbiprofen small intestine toxicity.

The present study compares the intestinal toxicity of nitro-flurbiprofen and flurbiprofen in order to determine their differential properties on tumour necrosis factor-alpha production and inducible nitric oxide synthase induction. Rats received one s.c. injection of flurbiprofen, nitro-flurbiprofen at equimolar dose of solvent. Twenty-four hours later, the rats were sacrificed and small intestine tissue was taken up for macroscopical quantification of ulceration, ex vivo production of tumour necrosis factor-alpha and nitrites, and determination of tissue inducible nitric oxide synthase and myeloperoxidase activities. Anti-inflammatory activity was examined in the carrageenan-induced paw edema model. We demonstrated that flurbiprofen induced dose-dependently small intestine production of tumour necrosis factor-alpha, nitrites, myeloperoxidase and inducible nitric oxide synthase activities. On the other hand, nitro-flurbiprofen did neither induce tumour necrosis factor-alpha nor nitrite production. Concurrently, no small intestine ulceration was observed with nitro-flurbiprofen whereas flurbiprofen induced dose-dependent ulceration. Nitro-flurbiprofen is devoid of intestinal toxicity despite inhibiting cyclooxygenase activity. This is associated with the absence of tumour necrosis factor-alpha and inducible nitric oxide synthase induction in normal rats. Nitro-flurbiprofen is an anti-inflammatory drug with a much more favorable gastro-intestinal toxicity profile than flurbiprofen.

Mechanism of enhancement of intestinal ulcerogenicity of S-aryl propionic acids by their R-enantiomers in the rat.

We previously observed a marked increase in gastrointestinal toxicity of rac-flurbiprofen compared to the therapeutically equivalent dose of the S enantiomer. This paper quantitates these observations and examines the mechanism by which this paradoxical toxicity occurs. We have evaluated the ulcer scores, mucosal neutrophil infiltration, by immunostaining of CD11/18 antigen, and mucosal neutrophil activity by myeloperoxidase measurement at two dose levels of (R)-, (S)-, and rac-flurbiprofen, administered over 30 days. Dose-response for intestinal ulcer production was observed for rac- and (S)-flurbiprofen; animals given (R)-flurbiprofen exhibited no ulcers. Yet rac-flurbiprofen proved to be twice as ulcerogenic as (S)-flurbiprofen. The mechanism of the exacerbation of gastrointestinal toxicity of (S)-flurbiprofen by the noncyclooxygenase inhibiting (R)-flurbiprofen is believed to be associated with its effect on ICAM-1 up-regulation. This is followed by neutrophil adhesiveness to ICAM-1 via the LFA-1 antigen on its surface and the extravasation of neutrophils into the tissue. We also examined the effect of high dose (R)-flurbiprofen vs vehicle over 15 days in animals in which ulcers had been produced by treatment with (S)-flurbiprofen for the previous 15 days. (R)-flurbiprofen did not sustain induced ulcers. The results of this study suggest that human studies be conducted to determine if enhanced gastrointestinal toxicity occurs in man. This is at issue since rac compounds of this class are available over the counter and others may be introduced.

R-flurbiprofen chemoprevention and treatment of intestinal adenomas in the APC(Min)/+ mouse model: implications for prophylaxis and treatment of colon cancer.

We used the C57BL/6J-APC(Min)/+ mouse (Min mouse) to evaluate the chemopreventive effects of R-flurbiprofen (R-FB), the noncyclooxygenase-inhibiting enantiomer of FB. Weanling Min mice were administered 6 weeks of oral treatment with R-FB using 2.5-25 mg/kg of R-FB once per day (q.d.), 2.5-10 mg/kg of R-FB twice per day (b.i.d.), and 5 mg/kg of R-FB b.i.d. challenged with a high saturated fat diet. At necropsy we determined tumor and ulcer numbers, tumor size, and plasma levels of R- and S-FB. A linear dose response was observed from 2.5 to 10 mg/kg of R-FB, regardless of whether the drug was administered as a single or divided dose. Reductions in tumor number were significant (P < or = 0.02) for doses of R-FB from 2.5 to 25 mg/kg/day. A dose of 5 mg/kg R-FB b.i.d. was able to overcome the doubling in tumor number associated with the high saturated fat diet. At 20 and 25 mg/kg/day R-FB, we obtained the maximum response with up to 90% inhibition of total tumor number. At these doses, however, there was toxicity and animal deaths. This toxicity was associated with ulceration, presumably resulting from the in vivo epimerization of R- to S-FB that occurs in the mouse. Thus, we evaluated the oral pharmacokinetics of R-FB and its conversion to S-FB in wild-type mice. These kinetics experiments revealed inversion rates of 7.3 and 11.0% for the 2.5 and 10 mg/kg R-FB doses, respectively. S-FB administered alone (0.5 and 2.0 mg/kg q.d.), in doses mimicking the concentrations of S-FB associated with the R to S epimerization of the doses of R-FB used in our experiments, had little or no antitumor efficacy (P > 0.05). Thus, we conclude that R-FB itself, not the S-FB resulting from epimerization in the mouse, inhibits adenoma formation in the Min mouse. In humans, where there is no R to S epimerization, it is possible that larger doses of R-FB can be used without causing cyclooxygenase inhibition and its resulting ulcerogenicity and other side effects. To assess the effect of R-FB on established adenomas, we allowed 40 Min mice to remain untreated until 70 days of age (the time of necropsy in the previous experiments) and then treated them for an additional 42 days with 10 mg/kg R-FB q.d. or 5 mg/kg R-FB b.i.d.. Both drug-treated groups demonstrated tumor numbers significantly less than that of the vehicle control (P < 0.01). Our results suggest that prophylaxis and treatment trials of R-FB should be extended to humans.