Effects of ibuprofen enantiomers and its coenzyme A thioesters on human prostaglandin endoperoxide synthases

Expanding Access to Optically Active Non-Steroidal Anti-Inflammatory Drugs via Lipase-Catalyzed KR of Racemic Acids Using Trialkyl Orthoesters as Irreversible Alkoxy Group Donors

Studies into the enzymatic kinetic resolution (EKR) of 2-arylpropanoic acids (‘profens’), as the active pharmaceutical ingredients (APIs) of blockbuster non-steroidal anti-inflammatory drugs (NSAIDs), by using various trialkyl orthoesters as irreversible alkoxy group donors in organic media, were performed. The enzymatic reactions of target substrates were optimized using several different immobilized preparations of lipase type B from the yeast Candida antarctica (CAL-B). The influence of crucial parameters, including the type of enzyme and alkoxy agent, as well as the nature of the organic co-solvent and time of the process on the conversion and enantioselectivity of the enzymatic kinetic resolution, is described. The optimal EKR procedure for the racemic profens consisted of a Novozym 435-STREM lipase preparation suspended in a mixture of 3 equiv of trimethyl or triethyl orthoacetate as alkoxy donor and toluene or n-hexane as co-solvent, depending on the employed racemic NSAIDs. The reported biocatalytic system provided optically active products with moderate-to-good enantioselectivity upon esterification lasting for 7–48 h, with most promising results in terms of enantiomeric purity of the pharmacologically active enantiomers of title APIs obtained on the analytical scale for: (S)-flurbiprofen (97% ee), (S)-ibuprofen (91% ee), (S)-ketoprofen (69% ee), and (S)-naproxen (63% ee), respectively. In turn, the employment of optimal conditions on a preparative-scale enabled us to obtain the (S)-enantiomers of: flurbiprofen in 28% yield and 97% ee, ibuprofen in 45% yield and 56% ee, (S)-ketoprofen in 23% yield and 69% ee, and naproxen in 42% yield and 57% ee, respectively. The devised method turned out to be inefficient toward racemic etodolac regardless of the lipase and alkoxy group donor used, proving that it is unsuitable for carboxylic acids possessing tertiary chiral centers.

Rectal Administration of Ibuprofen: Comparison of Enema and Suppository Form

Ibuprofen is a widely used and well-tolerated analgesic and antipyretic. It is desirable to have a formulation with a rapid rate of absorption because it is required for rapid pain relief and temperature reduction. Previous studies have described the pharmacokinetic profiles of ibuprofen suppository and the mean peak times of ibuprofen suppository were around 1.8 hours, indicating a slower rate of absorption. The aim of this study is to compare the pharmacokinetic parameters of rectal administration of ibuprofen between enema and suppository form in order to provide evidence for the faster absorption rates of ibuprofen enema. This study was a phase-1 clinical study, open-label, randomized and two-way crossover with one-week washout period comparing the absorption profile of equal dose of ibuprofen administered rectally in two treatment phases: ibuprofen suppository and enema. Blood samples were collected post dose for pharmacokinetic analyses. Tmax was analyzed using a Wilcoxon matched paired test. A standard ANOVA model, appropriate for bioequivalence studies was used and ratios of 90% confidence intervals were calculated. This study showed that Tmax for ibuprofen enema was less than half that of ibuprofen suppository (median 40 min vs. 90 min, respectively; p-value=0.0003). Cmax and AUC0-12 for ibuprofen enema were bioequivalent to ibuprofen suppository, as the ratio of test/reference=104.52%, 90% CI 93.41-116.95% and the ratio of test/reference=98.12%, 90%CI 93.34-103.16%, respectively, which fell within 80-125% bioequivalence limit. The overall extent of absorption was similar to the both, which were all well tolerated. In terms of Tmax, Ibuprofen enema was absorbed twice as quickly as from ibuprofen suppository. Therefore it is expected that an ibuprofen enema may provide faster onset of analgesic and antipyretic benefit.

Effect of treatment with resiniferatoxin in an experimental model of pulpal inflammatory in mice

AIM

To evaluate whether treatment with resiniferatoxin (RTX) is capable of lowering the plasma levels of PGE₂ and TNF-α, as well as histopathological parameters in inflammation of pulp tissue in a mouse experimental model.

METHODOLOGY

Ten groups of six BALB/c mice were formed as follows: healthy group (H_C ), healthy group treated with RTX (H_RTX ), two groups with pulp inflammation at 14 and 18 hours (PI₁₄ /PI₁₈ ), six groups with pulpal inflammation plus treatment with Ibuprofen (IBU₁₄ /IBU₁₈ ), dexamethasone (DEX₁₄ /DEX₁₈ ) and resiniferatoxin (RTX₁₄ /RTX₁₈ ) at 14 and 18 hours, respectively. Pulpal inflammation was induced through occlusal exposure of the pulp of the maxillary first molar. The plasma levels of PGE₂ and TNF-α and the histological parameters of the pulp tissue of the H_C and H_RTX groups were evaluated at the time of acquiring the animals. In the other groups, the plasma levels of PGE₂ and TNF-α and the histopathological parameters were evaluated at 14 and 18 hours after pulp damage. Plasma levels of PGE₂ and TNF-α were quantified by ELISA, and the histopathological parameters were evaluated by H/E staining. Statistical significance was determined by one-way analysis of variance (ANOVA) to test for overall differences between group means.

RESULTS

A significant increase (*p < .05) in plasma levels of PGE₂ and TNF-α occurred 14 and 18 hours after pulp damage. In addition, treatment with RTX significantly decreased (*p < .05) the plasma levels of PGE₂ and TNF-α at 14 and 18 hours after pulp damage, as well as the infiltrate of inflammatory cells at 18 hours after pulp damage, similarly to treatment with ibuprofen and dexamethasone.

CONCLUSION

It was possible to detect systemic levels of PGE₂ and TNF-α at 14 and 18 hours after pulp damage. Likewise, treatment with RTX was associated with an anti-inflammatory effect similar to treatment with ibuprofen and dexamethasone. These findings place resiniferatoxin as a therapeutic alternative in the treatment of inflammatory diseases in Dentistry.

Ibuprofen enantiomers in premature neonates with patent ductus arteriosus: Preliminary data on an unexpected pharmacokinetic profile of S(+)-ibuprofen

S(+)-ibuprofen (S-IBU) and R(-)-ibuprofen (R-IBU) concentrations were measured in 16 neonates with patent ductus arteriosus during a cycle of therapy (three intravenous doses of 10-5-5 mg kg^-1 at 24-h intervals), at the end of the first infusion and 6, 24, 48, and 72 h later. Data were analyzed with a PK model that included enantiomer elimination rate constants and the R- to S-IBU conversion rate constant. The T½ of S-IBU in the newborn was much longer than in adults (41.8 vs. ≈2 h), whereas the T½ of R-IBU appeared to be the same (2.3 h). The mean fraction of R- to S-IBU conversion was much the same as in adults (0.41 vs. ≈0.60). S-IBU concentrations measured 6 h after the first dose were higher than at the end of the infusion in 10 out of 16 cases, and in five cases, they remained higher even after 24 h. This behavior is unprecedented and may be attributable to a rapid R-to-S conversion overlapping with a slow S-IBU elimination rate. In 13 of the 16 neonates, S-IBU concentrations at 48 and/or 72 h were lower than expected, probably due to the rapid postnatal maturation of the newborn's liver metabolism.

Recommendations for standardizing nomenclature for dietary (poly)phenol catabolites

There is a lack of focus on the protective health effects of phytochemicals in dietary guidelines. Although a number of chemical libraries and databases contain dietary phytochemicals belonging to the plant metabolome, they are not entirely relevant to human health because many constituents are extensively metabolized within the body following ingestion. This is especially apparent for the highly abundant dietary (poly)phenols, for which the situation is compounded by confusion regarding their bioavailability and metabolism, partially because of the variety of nomenclatures and trivial names used to describe compounds arising from microbial catabolism in the gastrointestinal tract. This confusion, which is perpetuated in online chemical/metabolite databases, will hinder future discovery of bioactivities and affect the establishment of future dietary guidelines if steps are not taken to overcome these issues. In order to resolve this situation, a nomenclature system for phenolic catabolites and their human phase II metabolites is proposed in this article and the basis of its format outlined. Previous names used in the literature are cited along with the recommended nomenclature, International Union of Pure and Applied Chemistry terminology, and, where appropriate, Chemical Abstracts Service numbers, InChIKey, and accurate mass.

Albumin-Based Transport of Nonsteroidal Anti-Inflammatory Drugs in Mammalian Blood Plasma

Every day, hundreds of millions of people worldwide take nonsteroidal anti-inflammatory drugs (NSAIDs), often in conjunction with multiple other medications. In the bloodstream, NSAIDs are mostly bound to serum albumin (SA). We report the crystal structures of equine serum albumin complexed with four NSAIDs (ibuprofen, ketoprofen, etodolac, and nabumetone) and the active metabolite of nabumetone (6-methoxy-2-naphthylacetic acid, 6-MNA). These compounds bind to seven drug-binding sites on SA. These sites are generally well-conserved between equine and human SAs, but ibuprofen binds to both SAs in two drug-binding sites, only one of which is common. We also compare the binding of ketoprofen by equine SA to binding of it by bovine and leporine SAs. Our comparative analysis of known SA complexes with FDA-approved drugs clearly shows that multiple medications compete for the same binding sites, indicating possibilities for undesirable physiological effects caused by drug-drug displacement or competition with common metabolites. We discuss the consequences of NSAID binding to SA in a broader scientific and medical context, particularly regarding achieving desired therapeutic effects based on an individual's drug regimen.

Simulation-based suggestions to improve ibuprofen dosing for patent ductus arteriosus in preterm newborns

Purpose

Ibuprofen is the drug of choice for treatment of patent ductus arteriosus (PDA). There is accumulating evidence that current ibuprofen-dosing regimens for PDA treatment are inadequate. We aimed to propose an improved dosing regimen, based on all current knowledge.

Methods

We performed a literature search on the clinical pharmacology and effectiveness of ibuprofen. (R)- and (S)-ibuprofen plasma concentration-time profiles of different dosing regimens were simulated using a population pharmacokinetic model and evaluated to obtain a safe, yet likely more efficacious ibuprofen exposure.

Results

The most effective intravenous ibuprofen dosing in previous clinical trials included a first dose of 20 mg kg⁻¹ followed by 10 mg kg⁻¹ every 24 h. Simulations of this dosing regimen show an (S)-ibuprofen trough concentration of 43 mg L⁻¹ is reached at 48 h, which we assumed the target through concentration. We show that this target can be reached with a first dose of 18 mg kg⁻¹, followed by 4 mg kg⁻¹ every 12 h. After 96 h postnatal age, the dose should be increased to 5 mg kg⁻¹ every 12 h due to maturation of clearance. This twice-daily dosing has the advantage over once-daily dosing that an effective trough level may be maintained, while peak concentrations are substantially (22%) lower.

Conclusions

We propose to improve intermittent ibuprofen-dosing regimens by starting with a high first dose followed by a twice-daily maintenance dosing regimen that requires increase over time and should be continued until sufficient effect has been achieved.

Electronic supplementary material

The online version of this article (10.1007/s00228-018-2529-y) contains supplementary material, which is available to authorized users.

Use of the harmonic mean to the determination of dissociation constants of stereoisomeric mixtures of biologically active compounds

Herein we introduce the derivation of a mathematical expression to evaluate the dissociation constant of a mixture of stereoisomers in equal amounts (KdMIX), when the corresponding dissociation constants (Kd) or medium response (MR50) of the pure stereoisomers are known; the final equation takes the form of the harmonic mean. In order to validate the equation, we carried out a bibliographic search of experimental data of enantiomeric molecules with biological activity, considering the Kd's or MR50's of the isolated enantiomers as well as that of the racemate. The comparisons between the experimental dissociation constants of the mixtures (KdEXP or MR50EXP) and the calculated values (KdMIX or MR50MIX) were consistent; the similarity between these values is supported through statistical analyses of group comparison and simple linear correlation. The equation we obtained, which corresponds to the harmonic mean, was used to predict the values of KdMIX (or MR50MIX) or Kd (or MR50) in systems when only two of the experimental values are known: either the dissociation constants of both enantiomers or the Kd (or MR50) of one of the enantiomers and dissociation constant of the racemate.

A new investigation for some steroidal derivatives as anti-Alzheimer agents

We herein report the anti-Alzheimer activity of some synthesized heterocyclic pyrimidine and thiopyrimidine derivatives fused with steroidal structure. Twenty-one of these compounds were synthesized and conveniently screened for their anti-Alzheimer activities using of Flurbiprofen as the reference drug. Some of these compounds were demonstrated to exhibit remarkable activity and their β-amyloid (Aβ) lowering results as IC(50) values reported.

Effect of a cyclooxygenase-2 inhibitor on postexercise muscle protein synthesis in humans

Nonselective blockade of the cyclooxygenase (COX) enzymes in skeletal muscle eliminates the normal increase in muscle protein synthesis following resistance exercise. The current study tested the hypothesis that this COX-mediated increase in postexercise muscle protein synthesis is regulated specifically by the COX-2 isoform. Sixteen males (23 +/- 1 yr) were randomly assigned to one of two groups that received three doses of either a selective COX-2 inhibitor (celecoxib; 200 mg/dose, 600 mg total) or a placebo in double-blind fashion during the 24 h following a single bout of knee extensor resistance exercise. At rest and 24 h postexercise, skeletal muscle protein fractional synthesis rate (FSR) was measured using a primed constant infusion of [(2)H(5)]phenylalanine coupled with muscle biopsies of the vastus lateralis, and measurements were made of mRNA and protein expression of COX-1 and COX-2. Mixed muscle protein FSR in response to exercise (P < 0.05) was not suppressed by the COX-2 inhibitor (0.056 +/- 0.004 to 0.108 +/- 0.014%/h) compared with placebo (0.074 +/- 0.004 to 0.091 +/- 0.005%/h), nor was there any difference (P > 0.05) between the placebo and COX-2 inhibitor postexercise when controlling for resting FSR. The COX-2 inhibitor did not influence COX-1 mRNA, COX-1 protein, or COX-2 protein levels, whereas it did increase (P < 0.05) COX-2 mRNA (3.0 +/- 0.9-fold) compared with placebo (1.3 +/- 0.3-fold). It appears that the elimination of the postexercise muscle protein synthesis response by nonselective COX inhibitors is not solely due to COX-2 isoform blockade. Furthermore, the current data suggest that the COX-1 enzyme is likely the main isoform responsible for the COX-mediated increase in muscle protein synthesis following resistance exercise in humans.

Bioavailability of ibuprofen following oral administration of standard ibuprofen, sodium ibuprofen or ibuprofen acid incorporating poloxamer in healthy volunteers

Background

The aim of this study was to compare the pharmacokinetic properties of sodium ibuprofen and ibuprofen acid incorporating poloxamer with standard ibuprofen acid tablets.

Methods

Twenty-two healthy volunteers were enrolled into this randomised, single-dose, 3-way crossover, open-label, single-centre, pharmacokinetic study. After 14 hours' fasting, participants received a single dose of 2 × 200 mg ibuprofen acid tablets (standard ibuprofen), 2 × 256 mg ibuprofen sodium dihydrate tablets (sodium ibuprofen; each equivalent to 200 mg ibuprofen acid) and 2 × 200 mg ibuprofen acid incorporating 60 mg poloxamer 407 (ibuprofen/poloxamer). A washout period of 2-7 days separated consecutive dosing days. On each of the 3 treatment days, blood samples were collected post dose for pharmacokinetic analyses and any adverse events recorded. Plasma concentration of ibuprofen was assessed using a liquid chromatographic-mass spectrometry procedure in negative ion mode. A standard statistical ANOVA model, appropriate for bioequivalence studies, was used and ratios of 90% confidence intervals (CIs) were calculated.

Results

T_max for sodium ibuprofen was less than half that of standard ibuprofen (median 35 min vs 90 min, respectively; P = 0.0002) and C_max was significantly higher (41.47 μg/mL vs 31.88 μg/mL; ratio test/reference = 130.06%, 90% CI 118.86-142.32%). Ibuprofen/poloxamer was bioequivalent to the standard ibuprofen formulation, despite its T_max being on average 20 minutes shorter than standard ibuprofen (median 75 mins vs 90 mins, respectively; P = 0.1913), as the ratio of test/reference = 110.48% (CI 100.96-120.89%), which fell within the 80-125% limit of the CPMP and FDA guidelines for bioequivalence. The overall extent of absorption was similar for the three formulations, which were all well tolerated.

Conclusion

In terms of T_max, ibuprofen formulated as a sodium salt was absorbed twice as quickly as from standard ibuprofen acid. The addition of poloxamer to ibuprofen acid did not significantly affect absorption.

Chiral toxicology: it's the same thing...only different

Chiral substances possess a unique architecture such that, despite sharing identical molecular formulas, atom-to-atom linkages, and bonding distances, they cannot be superimposed. Thus, in the environment of living systems, where specific structure-activity relationships may be required for effect (e.g., enzymes, receptors, transporters, and DNA), the physiochemical and biochemical properties of racemic mixtures and individual stereoisomers can differ significantly. In drug development, enantiomeric selection to maximize clinical effects or mitigate drug toxicity has yielded both success and failure. Further complicating genetic polymorphisms in drug disposition, stereoselective metabolism of chiral compounds can additionally influence pharmacokinetics, pharmacodynamics, and toxicity. Optically pure pharmaceuticals may undergo racemization in vivo, negating single enantiomer benefits or inducing unexpected effects. Appropriate chiral antidotes must be selected for therapeutic benefit and to minimize adverse events. Enantiomers may possess different carcinogenicity and teratogenicity. Environmental toxicology provides several examples in which compound bioaccumulation, persistence, and toxicity show chiral dependence. In forensic toxicology, chiral analysis has been applied to illicit drug preparations and biological specimens, with the potential to assist in determination of cause of death and aid in the correct interpretation of substance abuse and "doping" screens. Adrenergic agonists and antagonist, nonsteroidal anti-inflammatory agents, SSRIs, opioids, warfarin, valproate, thalidomide, retinoic acid, N-acetylcysteine, carnitine, penicillamine, leucovorin, glucarpidase, pesticides, polychlorinated biphenyls, phenylethylamines, and additional compounds will be discussed to illustrate important concepts in "chiral toxicology."

Ibuprofen and other widely used non-steroidal anti-inflammatory drugs inhibit antibody production in human cells

The widely used non-steroidal anti-inflammatory drugs (NSAIDs) function mainly through inhibition of cyclooxygenases 1 and 2 (Cox-1 and Cox-2). Unlike Cox-1, Cox-2 is considered an inducible and pro-inflammatory enzyme. We previously reported that Cox-2 is upregulated in activated human B lymphocytes and using Cox-2 selective inhibitors that Cox-2 is required for optimal antibody synthesis. It is not known whether commonly used non-prescription and non-Cox-2 selective drugs also influence antibody synthesis. Herein, we tested a variety of Cox-1/Cox-2 non-selective NSAIDs, namely ibuprofen, tylenol, aspirin and naproxen and report that they blunt IgM and IgG synthesis in stimulated human peripheral blood mononuclear cells (PBMC). Ibuprofen had its most profound effects in inhibiting human PBMCs and purified B lymphocyte IgM and IgG synthesis when administered in the first few days after activation. As shown by viability assays, ibuprofen did not kill B cells. The implications of this research are that the use of widely available NSAIDs after infection or vaccination may lower host defense. This may be especially true for the elderly who respond poorly to vaccines and heavily use NSAIDs.

p53 is important for the anti-proliferative effect of ibuprofen in colon carcinoma cells

S-ibuprofen which inhibits the cyclooxygenase-1/-2 and R-ibuprofen which shows no COX-inhibition at therapeutic concentrations have anti-carcinogenic effects in human colon cancer cells; however, the molecular mechanisms for these effects are still unknown. Using HCT-116 colon carcinoma cell lines, expressing either the wild-type form of p53 (HCT-116 p53(wt)) or being p(HCT-116 p53(-/-)), we demonstrated that both induction of a cell cycle block and apoptosis after S- and R-ibuprofen treatment is in part dependent on p53. Also in the in vivo nude mice model HCT-116 p53(-/-) xenografts were less sensitive for S- and R-ibuprofen treatment than HCT-116 p53(wt) cells. Furthermore, results indicate that induction of apoptosis in HCT-116 p53(wt) cells after ibuprofen treatment is in part dependent on a signalling pathway including the neutrophin receptor p75(NTR), p53 and Bax.

Variants in the alpha-Methylacyl-CoA racemase gene and the association with advanced distal colorectal adenoma

BACKGROUND

alpha-Methylacyl-CoA racemase (AMACR), an enzyme involved in oxidation of branched chain fatty acids and cholesterol metabolites, as well as ibuprofen metabolism, is overexpressed in colorectal adenomas and cancer. AMACR gene variants have been associated with hereditary prostate cancer, but no studies have evaluated their etiologic role in colorectal carcinogenesis.

METHODS

We conducted a case-control study of 725 advanced distal colorectal adenoma cases and 729 frequency-matched controls from the screening arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Seven AMACR polymorphisms were genotyped. Unconditional logistic regression models were used to evaluate the associations adjusting for age at randomization and gender.

RESULTS

The 201L allele of S201L [TT versus CC: odds ratio (OR), 1.74; 95% confidence interval (95% CI), 1.15-2.62; TC versus CC: OR, 1.17; 95% CI, 0.93-1.49] and the 277E allele of K277E (GG versus AA: OR, 1.66; 95% CI, 1.03-2.68; GA versus AA: OR, 1.21; 95% CI, 0.96-1.53) were associated with increased risk of advanced distal colorectal adenoma (both P(trend) </= 0.02); the TGTGCG haplotype of six informative single nucleotide polymorphisms was also associated with increased risk (OR, 1.27; 95% CI, 1.03-1.55). Regular ibuprofen users who were homozygous for the variant allele at either M9V or D175G were at reduced risk for adenoma (both P(interaction) < 0.05).

CONCLUSION

Our study identified variants in AMACR associated with advanced distal colorectal adenoma and pointed to potential interactions with ibuprofen use.

Evidence of COX-2 independent induction of apoptosis and cell cycle block in human colon carcinoma cells after S- or R-ibuprofen treatment

Ibuprofen belongs to the 2-aryl propionic-acid derivatives and consists of two enantiomers, of which S-ibuprofen is a potent cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) inhibitor whereas the R-enantiomer is two to three orders of magnitude less potent to inhibit cyclooxygenases. Beside its positive effects on inflammation and pain several animal studies have shown that ibuprofen also inhibits tumor initiation and proliferation but the molecular mechanisms are not fully understood. To investigate to which extent the antiproliferative effect of ibuprofen depends on COX-inhibition we tested both enantiomers in different human colon carcinoma cell lines (HCA-7 express COX-1, COX-2 and produce high prostaglandin E2 level; HCT-15 express only COX-1 and produce nearly no prostaglandin E2). S- and R-ibuprofen reduced concentration dependently cell survival in both cell lines to a similar extent and caused a G0/G1 phase block as well as apoptosis. The cell cycle block was accompanied by a down regulation of cyclin A and B and an increase of the cell cycle inhibitory protein p27Kip-1. HCA-7 cells were less sensitive against the antiproliferative effects of ibuprofen enantiomers which was probably due to lower ibuprofen concentrations in this cell type. Also in the nude mice model both enantiomers inhibited tumor growth of HCA-7 and HCT-15 xenografts to a similar extent. However, in mice about 54% of R-ibuprofen was unidirectionally inverted to S-ibuprofen, thus the observed antitumorigenic effect of R-ibuprofen in vivo cannot solely be assigned to this enantiomer. In conclusion our data indicate that S- and R-ibuprofen show similar antiproliferative effects in human colon carcinoma cell lines irrespective of its COX-inhibiting potencies.

Elucidation of the mechanism of inhibition of cyclooxygenases by acyl-coenzyme A and acylglucuronic conjugates of ketoprofen

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit the cyclooxygenase (COX) isoforms which accounts for their clinical effects. The differential inhibition of COX-1 and COX-2 is not sufficient to explain the absence of a correlation between in vitro and in vivo effects, especially for 2-aryl-propionates, thus indicating the participation of metabolites. Conjugates to glucuronic acid and to coenzyme-A are mainly produced, and have been shown to be chemically reactive. Therefore, we studied the interaction of the ketoprofen metabolites with the COX enzymes. After incubation with bovine pulmonary artery endothelial cells (BPAEC), COX-1 was inhibited stereoselectively by S-ketoprofen acylglucuronide, and more significantly by CoA-thioester. After washing-out the medium, COX-1 activity was essentially recovered, indicating a reversible inhibition. In LPS-stimulated J774.2 cells, COX activity (mainly inducible COX-2) was inhibited reversibly and stereospecifically by S-ketoprofen glucuronide, whereas it disappeared totally and was not recovered after incubation with CoA-thioester. Correspondingly, inhibition of purified COX-2 with this compound was observed to be rapid and irreversible. Using an anti-ketoprofen antibody, COX immunoprecipitated from cells exhibited adduct formation for COX-2 but not for COX-1. This was observed after incubation with CoA-thioester, and, surprisingly, also with glucuronide. Molecular docking gave support to explain this discrepancy: the glucuronide was found to establish a strong interaction with Y115 located in the membrane binding domain, whereas the thioester was preferentially bound to the active site of the enzyme. Overall, our results suggest a contribution of CoA-thioester metabolites of carboxylic NSAIDs to their pharmacological action by irreversibly and selectively inhibiting COX-2.

Selective inhibition of Abeta42 production by NSAID R-enantiomers

Non-steroidal anti-inflammatory drugs (NSAIDs) have been associated with reduced risk for Alzheimer's disease (AD) and selected NSAIDs racemates suppress beta-amyloid (Abeta) accumulation in vivo and Abeta42 production in vitro. Clinical use of NSAIDs for preventing or treating AD has been hampered by dose-limiting toxicity believed to be due to cyclooxygenase (COX)-inhibition that is reportedly not essential for selective Abeta42 reduction. Profens have racemates and R-enantiomers were supposed to be inactive forms. Here we demonstrate that R-ibuprofen and R-flurbiprofen, with poor COX-inhibiting activity, reduce Abeta42 production by human cells. Although these R-enantiomers inhibit nuclear factor-kappaB (NF-kappaB) activation and NF-kappaB can selectively regulate Abeta42, Abeta42 reduction is not mediated by inhibition of NF-kappaB activation. Because of its efficacy at lowering Abeta42 production and low toxicity profile, R-flurbiprofen is a strong candidate for clinical development.

Limitation of the in vitro whole blood assay for predicting the COX selectivity of NSAIDs in clinical use

AIMS

To assess if the inhibitory potency of nonsteroidal anti-inflammatory drugs (NSAIDs) on cyclooxygenase (COX) isoenzymes, when given therapeutically in humans, can be predicted from their in vitro concentration-response curves using the whole blood assay.

METHODS

Twenty-four healthy male volunteers aged 20--27 years were recruited. Inhibition of blood COX isoenzymes was determined in vitro before any drug intake and ex vivo after single and repeated intake of either 7.5 mg meloxicam once, 400 mg ibuprofen three times daily or 75 mg diclofenac SR once, taken in a randomized cross-over design. Production of thromboxane B2 (TXB2) during clotting and of prostaglandin E2 (PGE2) during endotoxin exposure served as indicators of platelet COX-1 and monocyte COX-2 activity, respectively. Drugs were determined in plasma by h.p.l.c., with a chiral separation of ibuprofen and free fractions after equilibrium dialysis.

RESULTS

Intra-subject variation for COX-1 and COX-2 at baseline was at 26 +/- 18% and 18 +/- 13% respectively, and intersubject variation at 39% and 36%, respectively. The ratios of IC50s and, at best, of IC80s revealed diclofenac and meloxicam as selective COX-2 inhibitors and ibuprofen as a preferential COX-1 inhibitor in vitro. However, after oral intake, ibuprofen inhibited ex vivo COX-2 by 80% whereas diclofenac inhibited COX-1 by 70%. Meloxicam inhibited COX-1 from 30 to 55% depending on the repetition of the dose and increase in plasma concentrations. Using in vitro dose--response curves, the in vivo inhibitory potency of diclofenac was estimated adequately from its circulating concentration ([-0.18, 0.21] for COX-1 and [-0.13, -0.03] for COX-2) but this was not the case for ibuprofen on COX-2 ([-0.14, 0.27]) and meloxicam on COX-1 ([0.31, 1.05]). The limited predictability of the system was not improved through considering the unbound fraction of the drugs or the variable chiral inversion of ibuprofen.

CONCLUSIONS

Assessment of COX-2 selectivity based on in vitro studies and pharmacological modelling has a limited clinical relevance. There is a need to investigate COX selectivity at therapeutic plasma concentrations of NSAIDs using the ex vivo whole blood assay.

Synthesis and biological testing of Acyl-CoA-ketoprofen conjugates as selective irreversible inhibitors of COX-2

Ketoprofenoyl-CoA thioester 3 was synthesized by coupling ketoprofen to coenzyme A using the mixed anhydride method. Diastereoisomeric compounds 3a and 3b corresponding to the enantiomers of ketoprofen, were obtained in optically pure form by preparative HPLC. A non-acylating analogue, rac-3-(3-benzoylphenyl)-2-oxo-butanoyl-CoA (7) was also prepared. The biological evaluation suggested that 3a and 3b are reversible inhibitors of COX-1 and irreversible inhibitors of COX-2. Compound 7 appears to be a poor but selective inhibitor of COX-1.

Gastric toxicity of racemic ketoprofen and its enantiomers in rat: oxygen radical generation and COX-expression

OBJECTIVE AND DESIGN

The gastric toxicity of racemic-ketoprofen and its enantiomers (S(+)- and R(-)-ketoprofen), oxygen free radical generation and neutrophil infiltration in response to damage were evaluated in rats. Changes in prostaglandin synthesis, cyclooxygenase expression and glutathione metabolism were also studied.

MATERIALS AND METHODS

Studies were performed in Wistar rats. Drugs were given by oral administration: racemic-ketoprofen (100, 50 and 25 mg/kg body weight); S(+) and R(-)-ketoprofen (50, 25 and 12.5 mg/kg body weight). Determinations were made of gastric mucosal injury, lipid peroxidation, xanthine oxidase, myeloperoxidase and superoxide dismutase activities, glutathione levels, glutathione peroxidase and glutathione reductase activities, gastric prostaglandin synthesis (PGE2 levels) and COX-expression.

RESULTS

Racemic-ketoprofen dose-dependently exhibited the highest toxicity. In contrast, S(+)-ketoprofen at half the dose of the racemic compound proved to be less ulcerogenic. R(-)-ketoprofen was also less ulcerogenic, but when administered as the racemate exacerbated gastric ulceration caused by S(+)-ketoprofen. Drug administration produced significant increases in lipid peroxidation levels and xanthine-oxidase and a decrease in superoxide dismutase activity. Nevertheless the racemate induced the highest disturbances in oxidative metabolism. No changes in myeloperoxidase values and glutathione metabolism were found. Cyclooxygenase-1 immunoreactivity was observed and did not differ from that in control rats. Cyclooxygenase-2 could also be expressed after treatments.

CONCLUSIONS

R(-)-ketoprofen and S(+)-ketoprofen have a comparable gastric toxicity and they both have a better gastric toxicity profile as compared to the racemate. In addition to inhibition of prostaglandin synthesis, damage resulted in an increase of cyclooxygenase-2 protein expression. Oxygen radicals, including superoxide anions, could also be implicated.

Comparative pharmacology of S(+)-ibuprofen and (RS)-ibuprofen

Racemic ibuprofen, which contains equal quantities of R(-)-ibuprofen and S(+)-ibuprofen, has been used as an anti-inflammatory and analgesic agent for over 30 years. Although the S(+)-enantiomer is capable of inhibiting cyclooxygenase (COX) at clinically relevant concentrations, R(-)-ibuprofen is not a COX inhibitor. The two enantiomers of ibuprofen are therefore different in terms of their pharmacological properties and may be regarded as two different 'drugs'. They also differ in terms of their metabolic profiles. For example, R(-)-ibuprofen becomes involved in pathways of lipid metabolism and is incorporated into triglycerides along with endogenous fatty acids. S(+)-Ibuprofen does not appear to become involved in these unusual metabolic reactions, which is why S(+)-ibuprofen is regarded as being metabolically 'cleaner' than racemic ibuprofen. When racemic ibuprofen is given to humans, a substantial fraction of the dose of R(-)-ibuprofen (50%-60%) undergoes 'metabolic inversion' to yield S(+)-ibuprofen. On this basis, it has been argued that to obtain clinical effects that are comparable to those of a given dose of racemic ibuprofen, the dose of S(+)-ibuprofen would need to be about 75% of the dose of the racemate. However, this 'pharmacokinetic' rationale does not take into account the fact that inversion is not instantaneous, that there is variability in the extent of inversion between individuals, and that the kinetics of inversion may differ depending on the dosing situations. For example, the extent of inversion appears to be reduced when the racemate is given to patients experiencing acute pain. Recent studies have demonstrated that the clinical benefits of racemic ibuprofen can be derived from the administration of the single S(+)-enantiomer at a dose that is half that of the racemate. For example, 200 mg of S(+)-ibuprofen has been found to be superior or at least equivalent to 400 mg of the racemate in the relief of dental pain. Possible explanations for this higher than expected efficacy of S(+)-ibuprofen are considered.

Simultaneous fitting of R- and S-ibuprofen plasma concentrations after oral administration of the racemate

AIMS

To assess the pharmacokinetic equivalence of two different formulations of ibuprofen lysinate with special focus on the expected effects.

METHODS

Sixteen healthy volunteers received cross-over ibuprofen lysinate as either one tablet of 400 mg ('test') or two tablets of 200 mg ('reference'). Ibuprofen plasma concentrations were followed up for 10 h. Bioequivalence was assessed by standard noncompartmental methods. Ibuprofen plasma concentrations were fitted with a model that took bioinversion of R- to S-ibuprofen into account.

RESULTS

Peak plasma concentrations of R- and S-ibuprofen were 18.1 and 20 microg ml(-1) (test), and 18.2 and 20 microg ml(-1) (reference). Areas under the plasma concentration vs. time curves were 39.7 and 67.5 microg ml(-1) h (test), and 41.1 and 68.2 microg ml(-1) h (reference). Clearance of R-ibuprofen was 5.2 (test) and 5 l h(-1) (reference). A specific plasma concentration was reached with the test formulation about 5 min later than with the reference. Parameters from compartmental modelling were (given for R-and then for S-ibuprofen): body clearance: 4.9 and 4.64 l h(-1), central volume of distribution: 2.8 and 4.1 l, intercompartment clearance: 5.1 and 5.45 l h(-1), peripheral volume of distribution: 4.1 and 5.2 l. The absorption rate constant was 1.52 h(-1), and the test but not the reference formulation had a lag time of 0.1 h. Simulations showed similarity between formulations of the expected effects except for a calculated delay of 6 min with the test formulation.

CONCLUSIONS

Ibuprofen formulations were bioequivalent. The pharmacokinetic model may serve as a basis for future pharmacokinetic/pharmacodynamic calculations after administration of racemic ibuprofen.

Cyclooxygenase-independent actions of cyclooxygenase inhibitors

Several studies have demonstrated unequivocally that certain nonsteroidal anti-inflammatory drugs (NSAIDs) such as sodium salicylate, sulindac, ibuprofen, and flurbiprofen cause anti-inflammatory and antiproliferative effects independent of cyclooxygenase activity and prostaglandin synthesis inhibition. These effects are mediated through inhibition of certain transcription factors such as NF-kappaB and AP-1. The respective NSAIDs might interfere directly with the transcription factors, but their effects are probably mediated predominantly through alterations of the activity of cellular kinases such as IKKbeta, Erk, p38 MAPK, or Cdks. These effects apparently are not shared by all NSAIDs, since indomethacin failed to inhibit NF-kappaB and AP-1 activation as well as Erk and Cdk activity. In contrast, indomethacin was able to activate PPARgamma, which was not affected by sodium salicylate or aspirin. The differences in cyclooxygenase-independent mechanisms may have consequences for the specific use of these drugs in individual patients because additional effects may either enhance the efficacy or reduce the toxicity of the respective compounds.

Salicylate metabolites inhibit cyclooxygenase-2-dependent prostaglandin E(2) synthesis in murine macrophages

The poor cyclooxygenase (COX) inhibitor and major aspirin metabolite salicylic acid is known to exert analgesic and anti-inflammatory effects by still unidentified mechanisms. In RAW 264.7 macrophages, lipopolysaccharide (LPS)-induced COX-2-dependent synthesis of prostaglandin E(2) (PGE(2)) was suppressed by aspirin (IC(50) of 5. 35 microM), whereas no significant inhibition was observed in the presence of sodium salicylate and the salicylate metabolite salicyluric acid at concentrations up to 100 microM. However, the salicylate metabolite gentisic acid (2,5-dihydroxybenzoic acid; 10-100 microM) and salicyl-coenzyme A (100 microM), the intermediate product in the formation of salicyluric acid from salicylic acid, significantly suppressed LPS-induced PGE(2) production. In contrast, gamma-resorcylic acid (2,6-dihydroxybenzoic acid) as well as unconjugated coenzyme A failed to affect prostanoid synthesis, implying that the para-substitution of hydroxy groups and the activated coenzyme A thioester are important for COX-2 inhibition. Using real-time RT-PCR, none of the salicylate derivatives tested were found to interfere with COX-2 expression. Overall, our results suggest that certain metabolites of salicylic acid may contribute to the pharmacological action of its parent compound by inhibiting COX-2-dependent PGE(2) formation at sites of inflammation.

Choosing the right nonsteroidal anti-inflammatory drug for the right patient: a pharmacokinetic approach

Effective use of the growing number of nonsteroidal anti-inflammatory drugs (NSAIDs), a group that has recently been augmented by the introduction of the selective cyclo-oxygenase-2 inhibitors, requires adequate knowledge of their pharmacokinetics. After oral administration, the absorption of NSAIDs is generally rapid and complete. NSAIDs are highly bound to plasma proteins, specifically to albumin (>90%). The volume of distribution of NSAIDs is low, ranging from 0.1 to 0.3 L/kg, suggesting minimal tissue binding. NSAID binding in plasma can be saturated when the concentration of the NSAID exceeds that of albumin. Most NSAIDs are metabolised by the liver, with subsequent excretion into urine or bile. Enterohepatic recirculation occurs when a significant amount of an NSAID or its conjugated metabolites are excreted into the bile and then reabsorbed in the distal intestine. NSAID elimination is not dependent on hepatic blood flow. Hepatic NSAID elimination is dependent on the free fraction of NSAID within the plasma and the intrinsic enzyme activities of the liver. Renal elimination is not an important elimination pathway for NSAIDs, except for azapropazone. The plasma half-life of NSAIDs ranges from 0.25 to >70 hours, indicating wide differences in clearance rates. Hepatic or renal disease can alter NSAID protein binding and metabolism. Some NSAIDs with elimination predominantly via acylglucuronidation can have significantly altered disposition. Pharmacokinetics are also influenced by chronobiology, and many NSAIDs exhibit stereoselectivity. There appear to be relationships between NSAID concentration and effects. At therapeutically equivalent doses, NSAIDs appear to be equally efficacious. The major differences between NSAIDs are their therapeutic half-lives and safety profiles. NSAIDs undergo drug interactions through protein binding displacement and competition for active renal tubular secretion with other organic acids. When choosing the right NSAID for the right patient, individual patient-specific and NSAID-specific pharmacokinetic principles should be considered.

Inhibition of noxious stimulus-induced spinal prostaglandin E2 release by flurbiprofen enantiomers: a microdialysis study

Peripheral noxious stimuli have been shown to induce prostaglandin (PG) E2 release at the site of inflammation and in the spinal cord. The antiinflammatory and antinociceptive effects of cyclooxygenase-inhibiting drugs are thought to depend on the inhibition of PG synthesis. R-Flurbiprofen, however, does not inhibit cyclooxygenase activity in vitro but still produces antinociceptive effects. To find out whether R-flurbiprofen acts via inhibition of spinal PG release, concentrations of PGE2 and flurbiprofen in spinal cord tissue were assessed by microdialysis. The catheter was transversally implanted through the dorsal horns of the spinal cord at level L4. R- and S-flurbiprofen (9 and 27 mg kg(-1), respectively) were administered intravenously 10-15 min before subcutaneous injection of formalin into the dorsal surface of one hindpaw. Flurbiprofen was rapidly distributed into the spinal cord with maximal concentrations after 30-45 min. Baseline PGE2 dialysate concentrations were 100.6 +/- 6.4 pg ml(-1) (mean +/- SEM). After formalin injection they rose about threefold with a maximum of 299.4 +/- 68.4 pg ml(-1) at 7.5 min. After approximately 1 h PGE2 levels returned to baseline. Both flurbiprofen enantiomers completely prevented the formalin-induced increase of spinal PGE2 release and reduced PGE2 concentrations below basal levels. S- and R-flurbiprofen at 9 mg kg(-1) produced a minimum of 15.8 +/- 5.2 and 27.7 +/- 14.9 pg ml(-1), respectively, and 27 mg kg(-1) S- and R-flurbiprofen resulted in 11.7 +/- 1.7 and 9.3 +/- 4.7 pg ml(-1), respectively. PGE2 levels remained at the minimum up to the end of the observation period at 5 h. When 27 mg kg(-1) R-flurbiprofen was injected intravenously without subsequent formalin challenge, baseline immunoreactive PGE2 concentrations were not affected. S-Flurbiprofen (27 mg kg(-1)), however, led to a moderate reduction (approximately 40%). The data suggest that antinociception produced by R-flurbiprofen is mediated at least in part by inhibition of stimulated spinal PGE2 release and support the current view that increased spinal PGE2 release significantly contributes to nociceptive processing.

Chiral switches

Developments in synthetic and analytical chemistry have provided the tools to differentiate between two enantiomers (mirror images) of drugs or between the parent compound and metabolite(s) with respect to desired and undesired pharmacological effects. Several drugs are now marketed or being developed as single enantiomers in place of a previous racemic mixture, a process known as "chiral switching". It is easier to understand "pure" as opposed to "mixture" pharmacology but whether the promise of chiral (and metabolite) switches will translate into real clinical advances remains to be seen.

Cyclooxygenase-independent inhibition of smooth muscle cell mitogenesis by ibuprofen

The aryl-propionic acid derivative, ketoprofen, has been shown to inhibit fibroblast growth by a cylooxygenase-dependent mechanism [Sánchez, T., Moreno, J.J., 1999. S(+) enantiomer inhibits prostaglandin production and cell growth in 3T6 fibroblast cultures. Eur. J. Pharmacol. 370, 63-67]. The present study demonstrates that ibuprofen, another aryl-propionic acid derivative, inhibited platelet-derived growth factor-BB (20 ng/ml)-induced mitogenesis of cultured bovine coronary artery smooth muscle cells in a stereo-independent manner. In addition, pretreatment of the cells with indomethacin (3 microM) did not affect the inhibitory effects of ibuprofen enantiomers on smooth muscle cell mitogenesis. Thus, aryl-propionic acid-type cyclooxygenase inhibitors can inhibit cell proliferation by both, cyclooxygenase-dependent and -independent ways.

Chromatographic resolution, chiroptical characterization and preliminary pharmacological evaluation of the enantiomers of butibufen: a comparison with ibuprofen

Enantiomeric resolution of butibufen has been achieved on a cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phase with hexane-isopropanol-trifluoroacetic acid, 100:1.2:0.02 (v/v/v) as mobile phase at a flow rate of 1.0 mL min(-1). Semi-preparative isolation of the enantiomers then chiroptical characterization indicated that the order of elution was (-)-R- before (+)-S-butibufen. When tested for their effects on the cyclooxygenase and 5-lipoxygenase pathways of eicosanoid metabolism in calcium ionophore-activated rat peritoneal leukocytes it was found that (+)-S-butibufen inhibited generation of thromboxane B2 (TXB2) and prostaglandin E2 (PGE2) (cyclooxygenase pathway), with an IC50 of 1.5 microM (approx.), whereas the (-)-R enantiomer was essentially inactive. Neither enantiomer inhibited the 5-lipoxygenase pathway. In this regard, (+)-S-butibufen was approximately five times less potent as a cyclooxygenase inhibitor than (+)-S-ibuprofen. These results show the enantiomeric specificity and pathway selectivity of this novel non-steroidal anti-inflammatory drug.

Inhibition of anandamide hydrolysis by the enantiomers of ibuprofen, ketorolac, and flurbiprofen

The endogenous cannabimimetic anandamide is hydrolyzed by a fatty acid amide hydrolase to yield arachidonic acid and ethanolamine. In the present study, the regional distribution of the activity and its sensitivity to inhibition by the enantiomers of ibuprofen, ketorolac, and flurbiprofen has been investigated. The rate of [3H]anandamide hydrolysis was found in both 7-week-old and 90-week-old rats to be in the order hippocampus > cerebral cortex > cerebellum > striatum approximately midbrain, with higher rates of hydrolysis for the 7-week-old rats than for the 90-week-old rats. In whole brain (minus cerebellum), the R(-)-enantiomer of ibuprofen was a mixed-type inhibitor of anandamide hydrolysis and was approximately 2-3 times more potent than the S(+)-enantiomer, IC50 values of 230 and 750 microM, respectively, being found. A similar pattern of inhibition of anandamide hydrolysis was seen when intact C6 rat glioma cells were used. Ketorolac inhibited rat brain anandamide hydrolysis, with IC50 values of 50, 440, and 80 microM being found for the R-, S-, and R,S-forms, respectively. The IC50 value for R-flurbiprofen (60 microM) was similar to the IC50 value for the S-enantiomer (50 microM). These data demonstrate that there is no dramatic enantiomeric selectivity of NSAID compounds as inhibitors of fatty acid amide hydrolase enzyme(s) responsible for the hydrolysis of anandamide. The enantiomers of flurbiprofen and R-ketorolac are the most potent NSAID inhibitors of fatty acid amide hydrolase yet reported.

Effect of clofibrate on the chiral inversion of ibuprofen in healthy volunteers

OBJECTIVES

To determine the influence of the hypolipidemic drug clofibrate on the stereoselective metabolism of ibuprofen in humans.

METHODS

Healthy male subjects (n = 12) ingested a dose of 400 mg pseudoracemic ibuprofen (200 mg R-ibuprofen, 160 mg S-ibuprofen, and 40 mg 13C-S-ibuprofen) on two occasions after either pretreatment with clofibrate (2 gm/day over 1 week) or no pretreatment in a randomized order.

RESULTS

When subjects were pretreated with clofibrate, clearances of R-ibuprofen and 13C-S-ibuprofen increased significantly from 55.0 and 66.4 ml/min to 186.2 and 106.7 ml/min (p < 0.01), respectively. This increase was similarly reflected in the clearance by inversion of R-ibuprofen (control, 36.0 ml/min; treated, 118.8 ml/min; p < 0.01), as well as in the clearance by noninversion (control, 19.0 ml/min; treated, 67.4 ml/min; p < 0.01). Unbound clearance values significantly increased for R-ibuprofen (control, 19.5 L/min; treated, 38.7 L/min) but not for 13C-S-ibuprofen (11.8 versus 10.6 L/min, respectively). The fractional inversion of ibuprofen calculated from the urinary metabolite data was increased after clofibrate pretreatment (clofibrate group, 66.4%; control, 53.5%; p < 0.01). However, this was not evident when fractional inversion was calculated from the plasma concentration-time data for the unmetabolized drug.

CONCLUSIONS

Clofibrate altered the stereoselective disposition of ibuprofen in healthy volunteers by increased formation of R-ibuprofenoyl-coenzyme A rather than by an effect on oxidative metabolism of ibuprofen. This interaction has potential therapeutic implications.

Differential effect of selective cyclooxygenase-2 (COX-2) inhibitor NS 398 and diclofenac on formalin-induced nociception in the rat

Prostaglandins (PGs) are known to be involved in inflammatory and nociceptive processing. Since the discovery of at least two isozymes of cyclooxygenase (COX), inhibition of COX-2 has been suggested to be responsible for the therapeutic effects of nonsteroidal anti-inflammatory drugs (NSAIDs). In the present study, the effects of a rather selective COX-2 inhibitor, NS-398 (0.3-27 mg/kg i.p.), were studied using the rat formalin test as a model of acute nociception. Diclofenac (non-selective COX inhibitor; 0.3-27 mg/kg i.p.) was used as a control. NS-398 revealed antinociceptive activity only at a dose (27 mg/kg) which results in plasma concentrations which most likely do not selectively inhibit COX-2. By contrast, diclofenac inhibited formalin-induced flinching behaviour over the whole dose range tested. Our results suggest that PGs mediating nociception in the formalin test of the rat are most likely produced via the COX-1 as well as COX-2 pathways. Thus, in an acute model of nociception a non-selective COX inhibitor may offer advantages as compared to a selective COX-2 inhibitor.

Modulation of transcription factor NF-kappaB by enantiomers of the nonsteroidal drug ibuprofen

1. The nonsteroidal drug ibuprofen exists as an R(-)- and S(+)-enantiomer. Only the S(+)-enantiomer is an effective cyclo-oxygenase inhibitor, while the R(-)-enantiomer is inactive in this respect. Thus the molecular mechanism by which R(-)-ibuprofen exerts its anti-inflammatory and antinociceptive effects remains unknown. 2. In this study the effects of the enantiomers of ibuprofen on modulation of transcription factors have been examined with electrophoretic mobility-shift assay (EMSA), transient transfection experiments, confocal immunofluorescence and nuclear import experiments, to determine their selectivity and potency as inhibitors of the activation of transcription factor nuclear factor-kappaB (NF-kappaB). 3. R(-)-ibuprofen (IC50: 121.8 microM) as well as the S(+)-enantiomer (IC50: 61.7 microM) inhibited the activation of NF-kappaB in response to T-cell stimulation. The effect of ibuprofen was specific because, at concentrations up to 10 mM, ibuprofen did not affect the heat shock transcription factor (HSF) and the activation of NF-kappaB by prostaglandin E2 (PGE2). Very high concentrations of ibuprofen (20 mM) did not prevent NF-kappaB binding to DNA in vitro. Immunofluorescence and nuclear import experiments indicate that the site of ibuprofen action appeared to be upstream of the dissociation of the NF-kappaB-IkappaB-complex. 4. Our data raise the possibility that R(-)-ibuprofen exerts some of its effects by inhibition of NF-kappaB activation.

Clinical pharmacokinetics of ibuprofen. The first 30 years

Ibuprofen is a chiral nonsteroidal anti-inflammatory drug (NSAID) of the 2 arylpropionic acid (2-APA) class. A common structural feature of 2-APANSAIDs is a sp3-hybridised tetrahedral chiral carbon atom within the propionic acid side chain moiety with the S-(+)-enantiomer possessing most of the beneficial anti-inflammatory activity. Ibuprofen demonstrates marked stereoselectivity in its pharmacokinetics. Substantial unidirectional inversion of the R-(-) to the S-(+) enantiomer occurs and thus, data generated using nonstereospecific assays may not be extrapolated to explain the disposition of the individual enantiomers. The absorption of ibuprofen is rapid and complete when given orally. The area under the plasma concentration-time curve (AUC) of ibuprofen is dose-dependent. Ibuprofen binds extensively, in a concentration-dependent manner, to plasma albumin. At doses greater than 600mg there is an increase in the unbound fraction of the drug, leading to an increased clearance of ibuprofen and a reduced AUC of the total drug. Substantial concentrations of ibuprofen are attained in synovial fluid, which is a proposed site of action for nonsteroidal anti-inflammatory drugs. Ibuprofen is eliminated following biotransformation to glucuronide conjugate metabolites that are excreted in urine, with little of the drug being eliminated unchanged. The excretion of conjugates may be tied to renal function and the accumulation of conjugates occurs in end-stage renal disease. Hepatic disease and cystic fibrosis can alter the disposition kinetics of ibuprofen. Ibuprofen is not excreted in substantial concentrations into breast milk. Significant drug interactions have been demonstrated for aspirin (acetylsalicylic acid), cholestyramine and methotrexate. A relationship between ibuprofen plasma concentrations and analgesic and antipyretic effects has been elucidated.