Characterization of aspirin esterase activity in health and disease: In vitro and ex vivo studies.

Due to its ability to irreversibly inactivate platelet cyclooxygenase, low-dose aspirin (ASA) is the most widely used antithrombotic agent. Although, studies in specific types of patients with cardiovascular disease (CVD) have shown an incomplete inhibition of platelet's cyclooxygenase, which may increase the variability in drug response. Some aspects of ASA pharmacokinetics (PK) still need further investigation. In this study, we aimed to characterise the contribution of esterase enzymes to ASA hydrolysis in the peripheral blood and to assess their activity in 36 healthy subjects (Ctrl) and 77 CVD patients. To this aim, an in vitro assay testing esterase activity in parallel to a liquid chromatography-tandem mass spectrometry method simultaneously detecting ASA and its main metabolites salicylic (SA) and gentisic acids, have been developed. Michaelis-Menten constant (Km) calculation, ASA esterase isoforms characterisation, and ASA PK study were then achieved. The calculated Km identified plasma esterases as the enzymes with the higher affinity for the substrate compared to the RBC ones. Both rivastigmine and 4-bis-nitrophenyl phosphate inhibited plasma esterase activities, suggesting that acetylcholinesterase and carboxylesterase largely contribute to ASA hydrolysis. The feasibility of the method here developed has been explored in Ctrl and CVD patients. The effect of ASA treatment on enzyme activity was further evaluated on an age, sex and BMI matched subgroup of patients and Ctrl (n = 10 for each subgroup, on and off ASA). No overall variations were evidenced in both CVD and Ctrl groups, even when the effect of ASA treatment was tested. This result suggests the absence of any influence of disease state, drug treatments, and comorbidities on plasma esterase and the inability of ASA intake to induce esterase function. In conclusion, the method here developed allows a better characterisation of ASA esterase activity and could be helpful to define the PK-related determinants of ASA responsiveness in order to personalise regimen in specific pathological conditions.

Pharmacokinetics and Pharmacodynamics of Meloxicam in East Asian Populations: The Role of Ethnicity on Drug Response.

We aimed to reanalyze the differences in the pharmacokinetics (PKs) of meloxicam in East Asian populations based on a population approach using previously published data and to investigate the factors found in population PK analysis that affect the pharmacodynamics (PDs) of meloxicam. Population PK analysis was performed in 119 healthy male subjects (30 Japanese, 30 Chinese, 29 Korean, and 30 white) under strictly controlled trial conditions with regulated meals and a single lot of the drug. We found that CYP2C9 genotype and lean body mass were statistically significant predictors of clearance and volume of distribution, respectively. A statistical significant difference in the PK parameters between ethnic groups could not be identified. Simulations using PK/PD models showed that CYP2C9 genotype is the factor that affects the PDs of meloxicam. The genetic polymorphisms highlighted in this study would be beneficial for conducting clinical trials in East Asians with similar genetic backgrounds.

Evaluation of the dose-response relationship of oral robenacoxib in urate crystal-induced acute stifle synovitis in dogs.

The objective of the study was to establish the dose-response relationship for robenacoxib, a selective cyclooxygenase (COX)-2 inhibitor, in a urate crystal model of acute synovitis. In a randomized partial Latin square design trial, 12 beagle dogs were administered orally single doses of robenacoxib (0.5, 1, 2, 4 and 8 mg/kg), placebo and the positive control meloxicam (0.1 mg/kg), 3 h after injection of sodium urate crystals into a stifle joint. Dogs were assessed for weight bearing on a force plate and by subjective clinical orthopaedic observations. Robenacoxib produced dose-dependent improvement in weight bearing, and decreased pain on palpation and joint swelling, over the dose range 0.5-2 mg/kg with no further increase in effect over the range 2-8 mg/kg. For weight bearing on the force plate, the ED50 of robenacoxib was 0.6-0.8 mg/kg. The onset of action and time to peak effect of robenacoxib were faster (respectively, 2-2.5 h and 3-5 h) than for meloxicam (respectively, 3 h and 6 h). Robenacoxib significantly inhibited COX-2 at all doses, with dose-related activity. Robenacoxib did not inhibit COX-1 over the dose range 0.5-4 mg/kg, but produced transient inhibition at 8 mg/kg. In conclusion, oral administration of robenacoxib over the dose range 0.5-8 mg/kg demonstrated significant analgesic and anti-inflammatory efficacy in dogs.

Pharmacokinetic and bioequivalence studies of immediate release diclofenac potassium tablets (50mg) in healthy volunteers.

This study was conducted with the aim to determine the pharmacokinetic and bioequivalence of diclofenac potassium 50 mg test (F4) tablet formulation with reference product (Caflam). Present study was single dose, randomized, two phase cross over design, conducted in 12 healthy Pakistani volunteers and planned in accordance with FDA guidelines. In this study a simple, selective, sensitive and reproducible HPLC procedure was developed and validated for the estimation of diclofenac potassium in plasma. The process was validated in the range of 50 - 0.05 µg.mL-1 and used in bioequivalence trial of two products. Multiple blood samples were collected at various time points (0.5, 1, 2, 3, 4, 5, 6, 8, 10, 12 and 14 hr after treating volunteers with test (F4) and marketed reference brand. Plasma separation and deproteination were carried out with acetonitrile; samples (20µL) were injected using the validated HPLC method. Various pharmacokinetic parameters (compartmental and noncompartmental) were estimated using KineticaTM 4.4.1 (Thermo Electron Corp. USA). Bioequivalence among the products was established by calculating the 90% CI with log and non log transformed data for Cmaxcalc, Tmaxcalc, AUC0-∞, AUCtot and AUClast using two way ANOVA and Schirmann's Two one sided t- test. No significant difference was found between log and non-log data. The 90% confidence interval values using log transformed data for AUC0-∞ (0.997-1.024), AUCtot (1.004-1.031), AUClast (0.997 -1.024), Cmaxcalc (0.994-1.007) and Tmaxcalc (0.996-1.013) for the trial and reference products were found within the FDA acceptable limits of 0.8-1.25. Results were further verified by the Schirmann's one-sided t test. Results showed the bioequivalence of test and reference formulations. Both the products were well tolerated.

Stereoselective Pharmacokinetics of Ketoprofen After Oral Administration of Modified-Release Formulations in Caucasian Healthy Subjects.

BACKGROUND AND OBJECTIVES: Ketoprofen, a potent nonsteroidal anti-inflammatory drug, is clinically administered as a racemic mixture. One of the possible metabolism routes of ketoprofen is the inversion of the R- to S-enantiomer in the gastrointestinal tract. Ketoprofen, as a weak acid drug, might undergo recirculation through pancreatic/intestinal juices. The aim of the work was to investigate if a plasma-gastrointestinal tract recirculation of ketoprofen could explain its R-to-S chiral inversion after the oral administration of two modified-release formulations: a gastro-resistant delayed-release tablet (Reference) and an extended-release-plus-immediate-release bilayer tablet (Test). METHODS: Sixteen healthy Caucasian volunteers (eight women and eight men) participated in a ketoprofen bioequivalence study. Both formulations were administered with and without food. In both cases, standard meals were given throughout the experiment. R- and S-enantiomers were measured separately using a validated HPLC-UV chiral method. Mean concentration-time profiles of ketoprofen enantiomers in plasma were obtained for men and women. Area under the plasma concentration-time curve, maximum ketoprofen plasma concentration, and time-to-peak were also computed for both isomers, both modes of administration, and both sexes. S/R concentration ratio was assessed as an indicator of enantiomer chiral inversion rate. RESULTS: Differences in the pharmacokinetics of S- and R-ketoprofen enantiomers were found after the Test administration. S-Ketoprofen presented a lower plasma exposure compared to R-enantiomer. However, the S/R concentration ratio increased 1 h (in men) and 2 h (in women) after meal intakes. This was related to pancreatic and/or intestinal and/or biliary secretions of the drug, followed by reabsorption and conversion of the R- to the S-isomer. The lower intestinal pH reported for men would lead to a higher oral bioavailability of the Test formulation and a higher reabsorption of both ketoprofen isomers in this sex. Hence, a higher rise of the S/R concentration ratio could be observed in men. No significant differences between isomers exposure were detected in both sexes after the Reference administration. Different lag times were observed after fed and fasting administration of this formulation; however, drug absorption coincided with food ingestion. Then, drug recirculation affected the S/R ratio from the beginning of drug exposure, minimizing the difference between isomers disposition. CONCLUSIONS: R-to-S conversion rate could be mainly associated with several passages of the drug through the intestinal mucosa. The concentration-time profiles of ketoprofen in plasma after the administration of both formulations evidenced R-to-S conversion of recirculating drug following meal intakes.

Improved nonclinical pharmacokinetics and biodistribution of a new PPAR pan-agonist and COX inhibitor in nanocapsule formulation.

We report the in vitro release profile and comparative pharmacokinetics and biodistribution of a new peroxisome proliferator-activated receptor-γ agonist and cyclooxygenase inhibitor (Lyso-7) free or associated to poly(D,L-lactic acid) nanocapsules (NC) after intravenous administration in mice. Lyso-7 pertains to the class of insulin-sensitizing agents that shows potential beneficial effects in diabetes therapy. Monodispersed Lyso-7 NC with a mean diameter of 273 nm with high encapsulation efficiency (83%) were obtained. Lyso-7 dissolution rate was reduced (2.6-fold) upon loading in NC. The pharmacokinetic parameters were determined using a non-compartmental approach. In comparison with Lyso-7 in solution, the plasma-AUC increased 14-fold, the mean residence time 2.6-fold and the mean half-life (t1/2) 1.5-fold for Lyso-7-NC; the Lyso-7 plasma clearance, distribution volume and elimination rate were reduced 13, 10 and 1.4 fold, respectively, which indicates higher retention of encapsulated Lyso-7 in the blood compartment. Upon association with NC, organ exposure to Lyso-7 was higher in the heart (3.6-fold), lung (2.8-fold), spleen (2.3-fold), kidney (2-fold) and liver (1.8-fold) compared to Lyso-7 in solution. The analysis of whole data clearly indicates that body exposure to Lyso-7 was enhanced and the general toxicity reduced upon nanoencapsulation, allowing further evaluation of Lyso-7 in nonclinical and clinical studies.

Solid phase microextraction of diclofenac using molecularly imprinted polymer sorbent in hollow fiber combined with fiber optic-linear array spectrophotometry.

A simple solid phase microextraction method based on molecularly imprinted polymer sorbent in the hollow fiber (MIP-HF-SPME) combined with fiber optic-linear array spectrophotometer has been applied for the extraction and determination of diclofenac in environmental and biological samples. The effects of different parameters such as pH, times of extraction, type and volume of the organic solvent, stirring rate and donor phase volume on the extraction efficiency of the diclofenac were investigated and optimized. Under the optimal conditions, the calibration graph was linear (r(2)=0.998) in the range of 3.0-85.0 µg L(-1) with a detection limit of 0.7 µg L(-1) for preconcentration of 25.0 mL of the sample and the relative standard deviation (n=6) less than 5%. This method was applied successfully for the extraction and determination of diclofenac in different matrices (water, urine and plasma) and accuracy was examined through the recovery experiments.

Massive naproxen overdose with serial serum levels.

CONTEXT: Massive naproxen overdose is not commonly reported. Severe metabolic acidosis and seizure have been described, but the use of renal replacement therapy has not been studied in the context of overdose. CASE DETAILS: A 28-year-old man ingested 70 g of naproxen along with an unknown amount of alcohol in a suicidal attempt. On examination in the emergency department 90 min later, he was drowsy but had normal vital signs apart from sinus tachycardia. Serum naproxen level 90 min after ingestion was 1,580 mg/L (therapeutic range 25-75 mg/L). He developed metabolic acidosis requiring renal replacement therapy using sustained low efficiency dialysis (SLED) and continuous venovenous hemofiltration (CVVH) and had recurrent seizure activity requiring intubation within 4 h from ingestion. He recovered after 48 h. DISCUSSION: Massive naproxen overdose can present with serious toxicity including seizures, altered mental status, and metabolic acidosis. CONCLUSION: Hemodialysis and renal replacement therapy may correct the acid base disturbance and provide support in cases of renal impairment in context of naproxen overdose, but further studies are needed to determine the extraction of naproxen.

The pharmacokinetics and in vitro/ex vivo cyclooxygenase selectivity of parecoxib and its active metabolite valdecoxib in cats.

Parecoxib (PX) is an injectable prodrug of valdecoxib (VX, which is a selective cyclo-oxyganase-2 (COX-2)) inhibitor licensed for humans. The aim of the present study was to evaluate pharmacokinetics and in vitro/ex vivo cyclooxygenase selectivity of PX and VX in cats. In a whole blood in vitro study, PX did not affect either COX enzymes whereas VX revealed a COX-2 selective inhibitory effect in feline whole blood. The IC50 values of VX for COX-2 and COX-1 were 0.45 and 38.6 µM, respectively. Six male cats were treated with 2.5 mg/kg of PX by intramuscular injection. PX was rapidly converted to VX with a relatively short half-life of 0.4 h. VX achieved peak plasma concentration (2.79 ± 1.59 µg/mL) at 7 h following PX injection. The mean residence times for PX and VX were 0.43 ± 0.15 and 5.94 ± 0.88 h, respectively. In the ex vivo study, PX showed a COX-2 inhibition rate of about 70% in samples taken at 1, 2, 4 and 10 h after injection, with a significant difference compared to the control. In contrast, COX-1 was slightly inhibited, ranging from 0.7% to 9.7% of the control inhibition rate without any significant difference for 24 h after PX administration. The preliminary findings of the present research appear promising and encourage further studies to investigate whether PX can be successfully used in feline medicine.

Model-based analysis of thromboxane B2 and prostaglandin E2 as biomarkers in the safety evaluation of naproxen.

The assessment of safety in traditional toxicology protocols relies on evidence arising from observed adverse events (AEs) in animals and on establishing their correlation with different measures of drug exposure (e.g., Cmax and AUC). Such correlations, however, ignore the role of biomarkers, which can provide further insight into the underlying pharmacological mechanisms. Here we use naproxen as a paradigm drug to explore the feasibility of a biomarker-guided approach for the prediction of AEs in humans. A standard toxicology protocol was set up for the evaluation of effects of naproxen in rat, in which four doses were tested (7.5, 15, 40 and 80 mg/kg). In addition to sparse blood sampling for the assessment of exposure, thromboxane B2 and prostaglandin E2 were also collected in satellite groups. Nonlinear mixed effects modelling was used to evaluate the predictive performance of the approach. A one-compartmental model with first order absorption was found to best describe the pharmacokinetics of naproxen. A nonlinear relationship between dose and bioavailability was observed which leads to a less than proportional increase in naproxen concentrations with increasing doses. The pharmacodynamics of TXB2 and PGE2 was described by direct inhibition models with maximum pharmacological effects achieved at doses >7.5 mg/kg. The predicted PKPD relationship in humans was within 10-fold of the values previously published. Moreover, our results indicate that biomarkers can be used to assess interspecies differences in PKPD and extrapolated data from animals to humans. Biomarker sampling should be used systematically in general toxicity studies.

N-(3-Arylaminopyridin-4-yl)alkanesulfonamides as pyridine analogs of nimesulide: cyclooxygenases inhibition, anti-inflammatory studies and insight on metabolism.

Nimesulide, a COX-2 preferential inhibitor with a favorable gastric and cardiovascular safety profile, was responsible for some cases of acute liver failure attributed to the nitrobenzene ring. A series of analogs of nimesulide resulting from isosteric replacement of the nitrobenzene ring by the pyridine nucleus, was synthesized and their ability to inhibit both cyclooxygenases (COXs) isoforms was evaluated in vitro using a human whole blood model. Compounds 19c, 23b and 23c displayed an important inhibitory activity associated to a COX-2/COX-1 selectivity ratio similar to or higher than that of celecoxib. The anti-inflammatory activity and the ability of several compounds to decrease leukocyte infiltration were further evaluated in vivo in a model of a λ carrageenan-induced pleurisy. Plasma assays were performed on blood samples collected from rats and allowed us to identify the 4-position of the phenyl ring as a major metabolism site explaining the occasionally observed lack of correlation between in vitro and in vivo results.

Anandamide deficiency and heightened neuropathic pain in aged mice.

Damaging of peripheral nerves may result in chronic neuropathic pain for which the likelihood is increased in the elderly. We assessed in mice if age-dependent alterations of endocannabinoids contributed to the heightened vulnerability to neuropathic pain at old age. We assessed nociception, endocannabinoids and the therapeutic efficacy of R-flurbiprofen in young and aged mice in the spared nerve injury model of neuropathic pain. R-flurbiprofen was used because it is able to reduce neuropathic pain in young mice in part by increasing anandamide. Aged mice developed stronger nociceptive hypersensitivity after sciatic nerve injury than young mice. This was associated with low anandamide levels in the dorsal root ganglia, spinal cord, thalamus and cortex, which further decreased after nerve injury. In aged mice, R-flurbiprofen had only weak antinociceptive efficacy and it failed to restore normal anandamide levels after nerve injury. In terms of the mechanisms, we found that fatty acid amide hydrolase (FAAH) which degrades anandamide, was upregulated after nerve injury at both ages, so that this upregulation likely did not account for the age-dependent differences. However, enzymes contributing to oxidative metabolism of anandamide, namely cyclooxygenase-1 and Cyp2D6, were increased in the brain of aged mice, possibly enhancing the oxidative breakdown of anandamide. This may overwhelm the capacity of R-flurbiprofen to restore anandamide homeostasis and may contribute to the heightened risk for neuropathic pain at old age.

Powdered self-emulsified lipid formulations of meloxicam as solid dosage forms for oral administration.

The objectives of this study were to prepare a powdered self-emulsified (SEDDS) formulation of meloxicam and to compare its oral bioavailability against commercial Mobic tablets. The SEDDS formulation was prepared by in situ salt formation of meloxicam in a blend of lipid excipients and aqueous tris (hydroxymethyl) aminomethane solution. The liquid SEDDS was subsequently adsorbed on silica powder and was tested for size, flow, and crystal growth. The flowability index of the powdered SEDDS was borderline acceptable. Absence of crystal growth with storage was confirmed by DSC and PXRD studies. Dissolution of meloxicam from the powdered SEDDS was >90% vs. <12% for powdered meloxicam and <80% for the commercial tablets. Stability of the powdered formulations after storage in gelatin and HPMC capsules was also evaluated to study the effect of water migration from the fill into capsule shells. Capsules softened to a different extent as a function of fill material with HPMC capsules showing greater resistance to water migration. Finally, oral bioavailability of the formulations was evaluated in beagle dogs. Powdered meloxicam SEDDS formulation showed a 1.3-fold increase in AUC vs. commercial Mobic® tablets. Overall, this study described a novel SEDDS formulation of meloxicam and outlined a systematic approach to adsorbing and testing the flow and stability behavior of powdered SEDDS formulations.

A diclofenac suppository-nabumetone combination therapy for arthritic pain relief and a monitoring method for the diclofenac binding capacity of HSA site II in rheumatoid arthritis.

Diclofenac suppository, a non-steroidal anti-inflammatory drug (NSAID), is used widely in rheumatoid arthritis (RA) patients with severe arthritic pain. As the binding percentage of diclofenac to serum proteins is high, its free (unbound) concentration after rectal administration is low. To increase temporarily the free concentration of diclofenac and to enhance its analgesic effect by inhibiting the protein binding of diclofenac, the analgesic effect of diclofenac was examined before and after the start of an inhibitor administration to RA patients with insufficient control of arthritic pain, and the protein binding capacity of diclofenac was evaluated. Binding experiments were performed by ultrafiltration, and arthritic pain was recorded by the face scale. Free fractions of diazepam and diclofenac were augmented by increasing 6-methoxy-2-naphthylacetic acid (6-MNA; the active metabolite of the NSAID nabumetone) concentrations. The free fraction of diazepam increased after the start of nabumetone administration to RA patients, and arthritic pain relief was observed. These results suggest that 6-MNA has an inhibitory effect on the protein binding of diclofenac and the free fraction of diazepam can be used to evaluate the binding capacity of diclofenac. It is considered that diclofenac suppository-nabumetone combination therapy and the method for protein binding monitoring by diazepam can positively benefit RA patients with insufficient control of arthritic pain.

Indomethacin but not a selective cyclooxygenase-2 inhibitor inhibits esophageal adenocarcinogenesis in rats.

AIM: To evaluate the effects of indomethacin [dual cyclooxygenase (COX)-1/COX-2 inhibitor] and 3-(3,4-difluorophenyl)-4-(4-(methylsulfonyl) phenyl)-2-(5H)-furanone (MF-tricyclic) (COX-2 selective inhibitor) in a rat experimental model of Barrett's esophagus and esophageal adenocarcinoma. METHODS: A total of 112 surviving post-surgery rats were randomly divided into three groups: the control group (n = 48), which did not receive any treatment; the indomethacin group (n = 32), which were given 2 mg/kg per day of the COX-1/COX-2 inhibitor; and the MF-tricyclic group (n = 32), which received 10 mg/kg per day of the selective COX-2 inhibitor. Randomly selected rats were killed either 8 wk or 16 wk after surgery. The timing of the deaths was in accordance with a previous study performed in our group. Only rats that were killed at the times designated by the protocol were included in the study. We then assessed the histology and prostaglandin E2 (PGE2) expression levels in the rat esophagi. An additional group of eight animals that did not undergo esophagojejunostomy were included in order to obtain normal esophageal tissue as a control. RESULTS: Compared to a control group with no treatment (vehicle-treated rats), indomethacin treatment was associated with decreases in ulcerated esophageal mucosa (16% vs 35% and 14% vs 17%, 2 mo and 4 mo after surgery, respectively; P = 0.021), length of intestinal metaplasia in continuity with anastomosis (2 ± 1.17 mm vs 2.29 ± 0.75 mm and 1.25 ± 0.42 mm vs 3.5 ± 1.54 mm, 2 mo and 4 mo after surgery, respectively; P = 0.007), presence of intestinal metaplasia beyond anastomosis (20% vs 71.4% and 0% vs 60%, 2 mo and 4 mo after surgery, respectively; P = 0.009), severity of dysplasia (0% vs 71.4% and 20% vs 85.7% high-grade dysplasia, 2 mo and 4 mo after surgery, respectively; P = 0.002), and adenocarcinoma incidence (0% vs 57.1% and 0% vs 60%, 2 mo and 4 mo after surgery, respectively; P < 0.0001). Treatment with the selective COX-2 inhibitor, MF-tricyclic, did not prevent development of intestinal metaplasia or adenocarcinoma. In parallel, we observed a significant decrease in PGE2 levels in indomethacin-treated rats, but not in those treated with MF-tricyclic, at both 2 mo and 4 mo. Compared to control rats that did not undergo surgery (68 ± 8 ng/g, P = 0.0022 Kruskal-Wallis test) there was a significant increase in PGE2 levels in the esophageal tissue of the rats that underwent surgery either 2 mo (1332 ± 656 ng/g) or 4 mo (1121 ± 1015 ng/g) after esophagojejunostomy. However, no differences were found when esophageal PGE2 levels were compared 2 mo vs 4 mo post-esophagojejunostomy. At both the 2- and 4-mo timepoints, we observed a significant decrease in PGE2 levels in indomethacin-treated rat esophagi compared to those in either the control or MF-tricyclic groups (P = 0.049 and P = 0.017, respectively). No differences in PGE2 levels were found when we compared levels in rats treated with MF-tricyclic to not-treated rats. CONCLUSION: In this rat model of gastrointestinal reflux, indomethacin was associated with a decrease in the severity of esophagitis and reduced development of esophageal intestinal metaplasia and adenocarcinoma.

Pharmacokinetics and safety of single and multiple oral doses of meloxicam in adult horses.

BACKGROUND: Safety of meloxicam, a potent NSAID with selective COX-2 inhibition, has not been evaluated in horses. OBJECTIVES: To evaluate pharmacokinetics and safety of single and repeated oral doses of meloxicam in adult horses. ANIMALS: Forty-nine healthy, university-owned adult lightbreed horses. METHODS: Study conducted in 2 parts. Part I addressed pharmacokinetics of single oral dose meloxicam (0.6 mg/kg) in 16 horses. Part II, 33 horses were randomly assigned to 5 treatment groups to assess prolonged administration (0.6 mg/kg PO q24h for 6 weeks, n = 7) or higher doses (1.8 mg/kg, n = 7, or 3.0 mg/kg PO q24h, n = 7) of meloxicam for 2 weeks, compared with control horses (placebo, n = 7, or phenylbutazone, 4.4 mg/kg q12h on day 1, 2.2 mg/kg q12h for 4 days, then 2.2 mg/kg q24h for 9 days, n = 5). RESULTS: Maximum plasma concentration following a single oral dose of meloxicam was 915.1 ± 116.9 ng/mL and elimination half-life 10.2 ± 3.0 hours. Meloxicam (0.6 mg/kg, q24h, PO for 6 weeks) yielded plasma concentrations between 100 and 1000 ng/mL and was well tolerated by healthy adult horses. Administration of 3-5 times the recommended dose of meloxicam was associated with decreased total serum protein and albumin concentrations, gastrointestinal damage, renal damage, or bone marrow dyscrasia. PBZ administration was associated with the development right dorsal colitis, gastric ulceration, and protein losing enteropathy in 2 horses. CONCLUSIONS AND CLINICAL IMPORTANCE: Administration meloxicam at 0.6 mg/kg q24h was well tolerated for 6 weeks, without drug accumulation in plasma. Higher doses were associated with dose-dependent adverse effects typical of class of drugs.

Does ketoprofen or diclofenac pose the lowest risk to fish?

Ketoprofen and diclofenac are non-steroidal anti-inflammatory drugs (NSAIDs) often used for similar indications, and both are frequently found in surface waters. Diclofenac affects organ histology and gene expression in fish at around 1 µg/L. Here, we exposed rainbow trout to ketoprofen (1, 10 and 100 µg/L) to investigate if this alternative causes less risk for pharmacological responses in fish. The bioconcentration factor from water to fish blood plasma was <0.05 (4 for diclofenac based on previous studies). Ketoprofen only reached up to 0.6 ‰ of the human therapeutic plasma concentration, thus the probability of target-related effects was estimated to be fairly low. Accordingly, a comprehensive analysis of hepatic gene expression revealed no consistent responses. In some contrast, trout exposed to undiluted, treated sewage effluents bioconcentrated ketoprofen and other NSAIDs much more efficiently, according to a meta-analysis of recent studies. Neither of the setups is however an ideal representation of the field situation. If a controlled exposure system with a single chemical in pure water is a reasonable representation of the environment, then the use of ketoprofen is likely to pose a lower risk for wild fish than diclofenac, but if bioconcentration factors from effluent-exposed fish are applied, the risks may be more similar.

Pharmacokinetic, distribution, metabolism, and excretion of (Z)-2-amino-1,5-dihydro-1-methyl-5-[4-(mesyl)benzylidene]-4H-imidazol-4-one mesilate (ZLJ-601) in Sprague-Dawley rats.

(Z)-2-amino-1,5-dihydro-1-methyl-5-[4-(mesyl)benzylidene]-4H-imidazol-4-one mesilate (ZLJ-601) is an imidazolone COX/5-LOX inhibitor, which has excellent anti-inflammatory activity with an improved gastrointestinal safety profile. The purpose of this study was to evaluate the in vivo absorption, distribution, metabolism, and excretion of ZLJ-601 in Sprague-Dawley rats. After intravenous or intragastric administration to rats, the concentration of ZLJ-601 in plasma, bile, urine, feces and various types of tissues was detected by LC-MS. We also conducted the identification of metabolites using tandem mass spectrometry. After the intravenous administration, the t(1/2) ranged from 38.71 to 42.62 min and the AUC increased in a dose-proportional manner. After oral dosing, the plasma level of ZLJ-601 peaked at 28.33 min, having a C(max) value of 0.26 mg/l, and the bioavailability was only 4.92%. The highest tissue concentration of ZLJ-601 was observed in lung and kidney, but it was not found in brain. The majority of unchanged ZLJ-601 was excreted in urine (∼35.87%) within 36 h. Two main metabolites are the hydroxylation product and the glucuronide conjugate of the hydroxylation product.

Quantification of nimesulide in human plasma by high-performance liquid chromatography with ultraviolet detector (HPLC-UV): application to pharmacokinetic studies in 28 healthy Korean subjects.

Nimesulide is a selective COX-2 inhibitor that is as effective as the classical non-acidic nonsteroidal anti-inflammatory drugs in the relief of various pain and inflammatory conditions, but is better tolerated with lower incidences of adverse effects than other drugs. After oral dose of 100 mg nimesulide to western subjects, a mean maximal concentration (C(max)) of 2.86 ∼ 6.5 µg/mL was reached at 1.22 ∼ 2.75 h and mean t(1/2ß) of 1.8 ∼ 4.74 h. This study developed a robust method for quantification of nimesulide for the pharmacokinetics and suitability of its dosage in Korea and compared its suitability with other racial populations. Nimesulide and internal standard were extracted from acidified samples with methyl tert-butyl ether and analyzed by high-performance liquid chromatography with ultraviolet detection (HPLC-UV). The 28 healthy volunteers took 2 tablets of 100 mg nimesulide and blood concentrations were analyzed during the 24 h post dose. Several pharmacokinetic parameters were represented: AUC(0-infinity) = 113.0 mg-h/mL, C(max) = 12.06 mg/mL, time for maximal concentrations (T(max)) = 3.19 h and t(1/2ß) = 4.51 h. These were different from those of western populations as follows: AUC was 14.5% and C(max) was 28% that of of Korean subjects and T(max) and t(1/2ß) were also different. The validated HPLC-UV method was successfully applied for the pharmacokinetic studies of nimesulide in Korean subjects. Because the pharmacokinetics of nimesulide were different from western populations, its dosage regimen needs to be adjusted for Koreans.