Rapid high-performance liquid chromatographic assay for the simultaneous analysis of non-steroidal anti-inflammatory drugs in plasma

Development of salting-out extraction methodology for the determination of piroxicam from polymeric based nanocarriers and biological samples

The aim of the present study is to develop the polymeric nanoparticulate drug delivery systems of piroxicam and to evaluate the in-vitro characteristics such as entrapment efficiency, surface morphology, in-vitro drug release performance, etc. For this reason, a novel HPLC methodology was developed for the determination of piroxicam from its bulk form, pharmaceutical preparation, and nanoparticulate delivery systems. Furthermore, the developed formulation was applied to the rats and the biological samples (plasma, liver, heart, spleen, kidney, and lung homogenates) were analyzed by the developed HPLC method following a salting-out assisted liquid-liquid extraction strategy for the first time in the literature. A Kinetex C18 analytical column (150 mm × 4.6 mm i.d., 5 µm) was used as a stationary phase with a 0.8 mL/min flow rate of acetonitrile: phosphate buffer (40:60, v/v), the column oven was adjusted to 40 °C and detection wavelength is set to 360 nm. Developed method were validated as per selectivity, linearity, LOD, LOQ, precision, and accuracy specified in the International Council for Harmonisation guidelines. As a result of the present study, it has been shown that the analysis of piroxicam from the bulk form, pharmaceutical preparation, developed polymeric-based drug delivery system, and biological samples can be successfully performed and no interferences were observed in any matrix. The developed method was also successfully utilized to study the tissue distribution of piroxicam in rats.

Online clean-up setup for the determination of non-fluorescent acidic pharmaceutical drugs in complex biological samples

Analysis of acidic pharmaceuticals in complex biological samples is a challenging and formidable task due to the existence of interfering constituents within the sample matrices. Therefore, in order to avoid analytical column clogging and suppression/enhancement of signals of the analyte of interest, herein a simple, cost-effective and quick online ion chromatography based clean-up setup was introduced. This system was further coupled with a cost-effective homemade photochemically induced fluorimetric (PIF) setup for direct online conversion of non-fluorescent acidic pharmaceutical drugs into their respective fluorescent species. This advantageous system was favorably applied for the determination of four non-fluorescent acidic compounds in two complex biological samples (human serum and oral fluid) with minimum labor and organic solvent consumption. At optimized conditions, the developed method has shown good sensitivity, selectivity, satisfactory recoveries (88.68-102.14%) and low limits of detection (0.35-8.10 μg/L) with minimum or zero matrix effect.

Early detection of ketoprofen-induced acute kidney injury in sheep as determined by evaluation of urinary enzyme activities

OBJECTIVE

To evaluate early indicators of renal tissue destruction and changes in urinary enzyme activities in sheep during the first hours after acute kidney injury induced by administration of an overdose of an NSAID.

ANIMALS

12 adult female sheep.

PROCEDURES

Acute kidney injury was induced in 6 sheep by administration of ketoprofen (30 mg/kg, IV) and detected by evaluation of urinary protein concentration, iohexol clearance, and results of histologic examination. Six sheep served as control animals. Blood and urine samples were collected for up to 24 hours after administration of ketoprofen. Plasma concentrations of urea, creatinine, albumin, and total protein; plasma activities of alkaline phosphatase, acid phosphatase, γ-glutamyl transpeptidase (GGT), matrix metalloproteinase (MMP)-2, and MMP-9; and urinary creatinine and protein concentrations, specific gravity, and activities of alkaline phosphatase, acid phosphatase, GGT lactate dehydrogenase, N-acetyl-β-D-glucosaminidase (NAG), MMP-2, and MMP-9 were measured. Urinary protein concentration and enzyme activities were normalized on the basis of urinary creatinine concentrations and reported as ratios.

RESULTS

Many urinary enzyme-to-creatinine ratios increased before the plasma creatinine concentration exceeded the reference value. Urine NAG, lactate dehydrogenase, and acid phosphatase activities were increased beginning at 2 hours after ketoprofen administration, and alkaline phosphatase, GGT, and MMP-2 activities were increased beginning at 4 hours after ketoprofen administration. Most peak urinary enzyme-to-creatinine ratios were detected earlier than were the highest plasma creatinine and urea concentrations.

CONCLUSIONS AND CLINICAL RELEVANCE

Urinary enzyme activities were sensitive early indicators of acute kidney injury induced by an overdose of an NSAID in sheep.

In-vitro mutagenic potential and effect on permeability of co-administered drugs across Caco-2 cell monolayers of Rubus idaeus and its fortified fractions

This study investigated the mutagenic, anti-mutagenic and cytotoxic effects of acetone extract of raspberry, Rubus idaeus L. (v. Ottawa) Rosaceae, and the isolated and characterized ellagitannin and anthocyanin fractions thereof, suitable for food applications. The studied raspberry extract and fractions did not show any mutagenic effects determined in the miniaturized Ames test and were not cytotoxic to Caco-2 cells at the used concentrations. However, the anti-mutagenic properties were changed (i.e. decreased mutagenicity of 2-nitrofluorene in strain TA98, and slightly increased mutagenicity of 2-aminoanthracene in strain TA100) with metabolic activation. Further, their influence on the permeability of co-administered common drugs (ketoprofen, paracetamol, metoprolol and verapamil) across Caco-2 monolayers was evaluated. The apical-to-basolateral permeability of highly permeable verapamil was mostly affected (decreased) during co-administration of the raspberry extract or the ellagitannin fraction. Ketoprofen permeability was decreased by the ellagitannin fraction. Consumption of food rich in phytochemicals, as demonstrated here with chemically characterized raspberry extract and fractions, with well-absorbing drugs would seem to affect the permeability of some of these drugs depending on the components. Thus their effects on the absorption of drugs in-vivo cannot be excluded.

Evaluation of bioequivalence after oral, intramuscular, and intravenous administration of racemic ketoprofen in pigs

OBJECTIVE

To assess bioequivalence after oral, IM, and IV administration of racemic ketoprofen in pigs and to investigate the bioavailability after oral and IM administration.

ANIMALS

8 crossbred pigs.

PROCEDURES

Each pig received 4 treatments in a randomized crossover design, with a 6-day washout period. Ketoprofen was administered at 3 and 6 mg/kg, PO; 3 mg/kg, IM; and 3 mg/kg, IV. Plasma ketoprofen concentrations were measured by use of high-performance liquid chromatography for up to 48 hours. To assess bioequivalence, a 90% confidence interval was calculated for the area under the time-concentration curve (AUC) and maximum plasma concentration (C(max)).

RESULTS

Equivalence was not detected in the AUCs among the various routes of administration nor in C(max) between oral and IM administration of 3 mg/kg. The bioavailability of ketoprofen was almost complete after each oral or IM administration. Mean +/- SD C(max) was 5.09 +/- 1.41 microg/mL and 7.62 +/- 1.22 microg/mL after oral and IM doses of 3 mg/kg, respectively. Mean elimination half-life varied from 3.52 +/- 0.90 hours after oral administration of 3 mg/kg to 2.66 +/- 0.50 hours after IV administration. Time to peak C(max) after administration of all treatments was approximately 1 hour. Increases in AUC and C(max) were proportional when the orally administered dose was increased from 3 to 6 mg/kg.

CONCLUSIONS AND CLINICAL RELEVANCE

Orally administered ketoprofen was absorbed well in pigs, although bioequivalence with IM administration of ketoprofen was not detected. Orally administered ketoprofen may have potential for use in treating pigs.

Effects of urine alkalization and activated charcoal on the pharmacokinetics of orally administered carprofen in dogs

OBJECTIVE

To investigate the effects of oral administration of activated charcoal (AC) and urine alkalinization via oral administration of sodium bicarbonate on the pharmacokinetics of orally administered carprofen in dogs.

ANIMALS

6 neutered male Beagles.

PROCEDURES

Each dog underwent 3 experiments (6-week interval between experiments). The dogs received a single dose of carprofen (16 mg/kg) orally at the beginning of each experiment; after 30 minutes, sodium bicarbonate (40 mg/kg, PO), AC solution (2.5 g/kg, PO), or no other treatments were administered. Plasma concentrations of unchanged carprofen were determined via high-performance liquid chromatography at intervals until 48 hours after carprofen administration. Data were analyzed by use of a Student paired t test or Wilcoxon matched-pairs rank test.

RESULTS

Compared with the control treatment, administration of AC decreased plasma carprofen concentrations (mean +/- SD maximum concentration was 85.9 +/- 11.9 mg/L and 58.1 +/- 17.6 mg/L, and area under the time-concentration curve was 960 +/- 233 mg/L x h and 373 +/- 133 mg/L x h after control and AC treatment, respectively). The elimination half-life remained constant. Administration of sodium bicarbonate had no effect on plasma drug concentrations.

CONCLUSIONS AND CLINICAL RELEVANCE

After oral administration of carprofen in dogs, administration of AC effectively decreased maximum plasma carprofen concentration, compared with the control treatment, probably by decreasing carprofen absorption. Results suggest that AC can be used to reduce systemic carprofen absorption in dogs receiving an overdose of carprofen. Oral administration of 1 dose of sodium bicarbonate had no apparent impact on carprofen kinetics in dogs.

On-line sample extraction and enrichment of non-steroidal anti-inflammatory drugs by pre-column in capillary liquid chromatography mass spectrometry

A rapid and sensitive analytical method has been developed for the simultaneous determination of 16 non-steroidal anti-inflammatory drugs (NSAIDs) in human plasma by capillary liquid chromatography (LC) and quadrupole mass spectrometry with electrospray ionization operated in the negative ion mode. The sample clean-up and enrichment on a pre-column were accomplished on-line to improve the sensitivity. This method greatly reduced sample preparation time and sample volume compared with off-line sample extraction methods and conventional LC methods, respectively. The recoveries of NSAIDs from human plasma were 56.7-96.9%. The total analytical time for a single analytical run was approximately 15 min. The detection limits of NSAIDs were 0.001-0.075 microg ml(-1) using a selected ion monitoring mode.

Direct determination of non-steroidal anti-inflammatory drugs by column-switching LC–MS

A method for determination of 16 non-steroidal anti-inflammatory drugs (NSAIDs) in human plasma samples without time-consuming sample pre-treatments was developed. The system consisted of two pumps for mobile phase delivery, a six-port switching valve, a pre-column (Oasis HLB Cartridge Column), and a reversed phase analytical column (COSMOSIL 3C18-MS-II). The analytes were trapped on the precolumn and subsequently separated on the analytical column. The present method allowed on-line sample clean-up and enrichment, leading to improved sensitivity without any tedious sample preparation. The recoveries of NSAIDs from human plasma by column-switching were greater than 72.6%. The total analysis time for a single analytical run was approximately 11 min. The detection limits of NSAIDs were 0.0025 to 0.2 microg/mL using the selected ion monitoring mode.

Rapid and simultaneous determination of nonsteroidal anti-inflammatory drugs in human plasma by LC–MS with solid-phase extraction

A rapid, selective and sensitive analytical method for the simultaneous determination of 16 nonsteroidal anti-inflammatory drugs (NSAIDs) in human plasma was carried out using Oasis HLB solid-phase extraction (SPE), followed by reversed-phase high-performance liquid chromatography and quadrupole mass spectrometry with electrospray ionization operated in the negative ion mode. The recoveries of NSAIDs from human plasma by SPE were greater than 76.7%. The use of a short column packed with small particles enabled rapid and simultaneous determination within 7 min. The detection limits for the NSAIDs were 0.01-0.9 mug/ml using the selected ion monitoring mode.

Simultaneous determination of naproxen, ketoprofen and phenol red in samples from rat intestinal permeability studies: HPLC method development and validation

A simple reversed-phase high performance liquid chromatographic method with UV detection at 270 nm was developed for simultaneous quantitation of ketoprofen and naproxen sodium along with phenol red as a non-absorbable marker for in situ permeability studies. The mobile phase was a mixture of 20% methanol, 28% of acetonitrile, 52% water and 0.4 ml triethylamine (adjusted to pH 3.2 using orthophosphoric acid). Analysis was run at a flow of 1.5 ml/min with a 20 min run time. The calibration curves were linear for all three compounds (r>0.999) across the concentration range of 15.6-250 microg/ml with a limit of quantitation of 0.3, 0.25 and 0.2 ng/ml for naproxen, ketoprofen and phenol red, respectively. The coefficient of variation for intra-assay and inter-assay precision was less than or equal to 5.3% and the accuracy was between 95.36 and 101.6%. Using the SPIP technique and the suggested HPLC method for sample analysis, the mean values of 1.17e(-4) (+/-0.28) cm/s and 0.97e(-4) (+/-0.2) cm/s were obtained for naproxen and ketoprofen, respectively.

Combined liquid and solid-surface room temperature fluorimetric determination of naproxen and salicylate in serum

A rapid and sensitive method for the determination of naproxen and salicylate in serum is presented. The employed strategy combines solid-phase extraction on a reverse-phase membrane with spectrofluorimetry. Solid-phase extraction under optimum pH conditions makes NX to be retained over the solid surface (where it is directly determined by a fluorimetric technique). Salicylate passes through the disk and is also fluorimetrically determined, but in solution. The linear calibration ranges for NX in the membrane and salicylate in solution were 0.014-0.250 and 0.010-0.250 microg ml(-1), respectively. The lowest value, in each case, is the corresponding limit of quantitation. The performance of the method is demonstrated with the successful determination of both drugs in spiked and real human serum samples.

Simultaneous quantitation of etoricoxib, salicylic acid, valdecoxib, ketoprofen, nimesulide and celecoxib in plasma by high-performance liquid chromatography with UV detection

A specific, accurate, precise and reproducible high performance liquid chromatography (HPLC) method was developed and validated for the simultaneous quantitation of etoricoxib, salicylic acid, valdecoxib, ketoprofen, nimesulide and celecoxib in human plasma. The method employed a simple liquid-liquid extraction of etoricoxib, salicylic acid, valdecoxib, ketoprofen, nimesulide and celecoxib and internal standard (IS, DRF-4367) from human plasma (500 microL) into acetonitirile. The organic layer was separated and evaporated under a gentle stream of nitrogen at 40 degrees C. The residue was reconstituted in the mobile phase and injected onto a Kromasil KR 100-5C18 column (4.6 x 250 mm, 5 microm). The chromatographic separation was achieved by gradient elution consisting of 0.05 M formic acid (pH 3)-acetonitrile-methanol-water at a flow rate of 1.0 mL/min. The eluate was monitored using an ultraviolet (UV) detector set at 235 nm. The ratio of peak area of each analyte to IS was used for quantification of plasma samples. Nominal retention times of etoricoxib, salicylic acid, valdecoxib, ketoprofen, nimesulide, IS and celecoxib were 15.63, 17.20, 21.66, 24.95, 26.27, 30.24 and 32.22 min, respectively. The standard curve for etoricoxib, salicylic acid, valdecoxib, ketoprofen and celecoxib was linear (r2 > 0.999) in the concentration range 0.1-50 microg/mL and for nimesulide (r2 > 0.999) in the concentration range 0.5-50 microg/mL. Absolute recovery was >83% from human plasma for all the analytes and IS. The lower limit of quantification (LLOQ) of nimesulide was 0.5 microg/mL and for etoricoxib, salicylic acid, valdecoxib, ketoprofen and celecoxib the LLOQ was 0.1 microg/mL. The inter- and intra-day precisions in the measurement of QC samples, 0.1, 0.3, 15.0 and 40.0 microg/mL (for all analytes except nimesulide), were in the range 2.29-9.37% relative standard deviation (RSD) and 0.69-10.28% RSD, respectively. For nimesulide the inter- and intra-day precisions in the measurement of quality control (QC) samples, 0.5, 1.5, 15.0 and 40.0 microg/mL, were in the range 3.21-7.37% RSD and 0.97-7.06% RSD, respectively. Accuracy in the measurement of QC samples for all analytes was in the range 91.03-106.38% of the nominal values. All analytes including IS were stable in the battery of stability studies, viz. bench top, autosampler and freeze-thaw cycles. Stability of all analytes was established for 21 days at -20 degrees C. The application of the assay in an oral pharmacokinetic study in rats co-administered with celecoxib and valdecoxib is described.

Simultaneous determination of arylpropionic acidic non-steroidal anti-inflammatory drugs in pharmaceutical formulations and human plasma by HPLC with UV detection

A simple and sensitive high-performance liquid chromatography-UV detection method was developed for the simultaneous determination of non-steroidal anti-inflammatory drugs (NSAIDs) having an arylpropionic acid moiety in pharmaceutical formulations and human plasma. Isocratic separation was employed on ODS column (250 x 4.6 mm i.d., 5 microm) at ambient temperature. The mobile phase consisted of acetonitrile, phosphate buffer (pH 3.5; 50 mM), methanol and tetrahydrofuran. The NSAIDs in the eluent were monitored under a wavelength-programme to provide their maximum absorbance. Mefenamic acid was used as an internal standard. Drugs were found to be 96.8-101.9% of their label claim in pharmaceutical formulations. One hundred microliters of human plasma samples were pretreated with a simple liquid-liquid extraction using ethyl acetate. The detection limits of compounds studied at a signal-to-noise ratio of 3 were 11.5-75 ng/ml in human plasma samples. The proposed method is simple, selective and could be applicable for routine analysis of arylpropionic acidic NSAIDs in pharmaceutical as well as in human plasma samples.

Determination of fenoprofen in serum by capillary isotachophoresis

A isotachophoretic method with conductivity detection was developed and validated to directly determine fenoprofen in human serum. The leading electrolyte contained hydrochloric acid (10 mmol/l), 6-aminocaproic acid (pH 4.8) and polyvinylpyrrolidone (0.1%). The terminating electrolyte was 4-morpholineethanesulfonic acid (5 mmol/l). The calibration curve was linear over the concentration range 0.02-0.40 mmol/l. Within-day standard deviation ranged from 0.001 to 0.004 and between-day standard deviation ranged from 0.001 to 0.004. The limit of determination was 0.02 mmol/l. The assay was employed to determine serum concentration of fenoprofen in patients.

Simultaneous determination of diclofenac and oxybuprocaine in human aqueous humor with HPLC and electrochemical detection

A sensitive and selective bioanalytical method for simultaneous determination of diclofenac and oxybuprocaine in human aqueous humor using reversed-phase HPLC and electrochemical detection is described. Chromatographic separation was achieved by using a Regis SPS 100 RP-8 column (5 microns; 150 x 4.6 mm I.D.). This support is coated with a hydrophilic polyoxyethylenepolymer. It allows protein-containing samples to be injected directly onto the column. The electrochemical detector permit a detection limit of 500 pg diclofenac per ml (daily relative standard deviation 6.3%) and 50 ng oxybuprocaine per ml (daily R.S.D. 2.6%), respectively. Results of administered and measured drug-concentrations in time dependent decrease are presented.

Single- and multiple-dose pharmacokinetic comparison of a sustained-release tablet and conventional tablets of naproxen in healthy volunteers

The pharmacokinetics of a new sustained-release tablet of naproxen (500 mg once daily) were compared with a conventional tablet (250 mg twice daily) after single- or multiple-dose oral administration in healthy volunteers using an open, randomized two-way crossover experimental design. Naproxen was well absorbed from the sustained-release tablet (approximately 97%) compared with the conventional tablet. Pharmacokinetic data showed that the sustained-release formulation reached significantly delayed mean peak plasma levels (Cmax) in both single- and multiple-dose studies and lower Cmax in a single-dose study than the conventional formulation. However, there were no statistically significant differences in other pharmacokinetic parameters, including area under the concentration-time curve (AUC), elimination half-life (t1/2), and elimination rate constant (Ke), in either single- or multiple-dose studies between the two treatments. In addition, there were no significant differences between formulations in Cmax, minimum plasma concentration (Cmin), and fluctuation index in the multiple-dose study.

Determination of the novel non-steroidal anti-inflammatory drug lornoxicam and its main metabolite in plasma and synovial fluid

A rapid and sensitive HPLC method for the determination of the non-steroidal anti-inflammatory drug lornoxicam in plasma samples of humans and laboratory animals is described. After addition of the internal standard (tenoxicam) the plasma sample is acidified and extracted either by dichloromethane via Extrelut columns or by solid-phase extraction using C18 columns. After evaporation of the solvent the separation is performed on a C18 column in isocratic mode with a mobile phase consisting of 0.1 M phosphate buffer (pH 6.0)-methanol and detection at 372 nm. The limit of determination was set to 10 ng/ml using 0.5 ml of sample but can be extended down to 2.0 ng/ml plasma. Using solid-phase extraction with C18 columns both lornoxicam and its main metabolite 5'-hydroxylornoxicam can be determined while extraction via Extrelut was used in studies where only lornoxicam was to be determined. This method was used successfully in several thousand samples of pharmacokinetic and bioavailability studies in animals and in humans.

Clinical pharmacokinetics of diclofenac. Therapeutic insights and pitfalls

Diclofenac is a nonsteroidal anti-inflammatory drug (NSAID) of the phenylacetic acid class. When given orally the absorption of diclofenac is rapid and complete. Diclofenac binds extensively to plasma albumin. The area under the plasma concentration-time curve (AUC) of diclofenac is proportional to the dose for oral doses between 25 to 150 mg. Substantial concentrations of drug are attained in synovial fluid, which is the proposed site of action for NSAIDs. Concentration-effect relationships have been established for total bound, unbound and synovial fluid diclofenac concentrations. Diclofenac is eliminated following biotransformation to glucoroconjugated and sulphate metabolites which are excreted in urine, very little drug is eliminated unchanged. The excretion of conjugates may be related to renal function. Conjugate accumulation occurs in end-stage renal disease; however, no accumulation is apparent upon comparison of young and elderly individuals. Dosage adjustments for the elderly, children or for patients with various disease states (such as hepatic disease or rheumatoid arthritis) may not be required. Significant drug interactions have been demonstrated for aspirin (acetylsalicylic acid), lithium, digoxin, methotrexate, cyclosporin, cholestyramine and colestipol.

Clinical pharmacokinetics of sulindac. A dynamic old drug

Sulindac is a nonsteroidal anti-inflammatory drug (NSAID) of the indene acetic acid class. The absorption of sulindac is rapid when given orally. Sulindac is reversibly metabolised to sulindac sulphide which has anti-inflammatory and analgesic properties and is irreversibly metabolised to sulindac sulphone which has been suggested to possess antiproliferative effects against tumours. Sulindac and its sulphide and sulphone metabolites bind extensively to plasma albumin. Sulindac is eliminated following bio-transformation; sulindac and sulindac sulphone and their respective glucurooconjugated metabolites are excreted in urine; however only a small amount of the sulindac sulphide metabolite is eliminated in urine. Following long term twice daily administration both sulindac and its metabolites accumulate in plasma. Both patients with cirrhosis and the elderly demonstrate elevated concentrations of all species upon long term sulindac administration as compared with a single dose. The disposition of sulindac and its metabolites may be tied to renal function. In end-stage renal disease, increased free fractions of all species and accumulation of the sulphide and sulphone metabolites, and to a lesser extent sulindac, occurs. Significant drug interactions have been demonstrated for dimethylsulphoxide, cyclosporin, furosemide (frusemide), hydrochlorothiazide, methotrexate and cholestyramine.

Sensitive capillary gas chromatographic-mass spectrometric-selected-ion monitoring method for the determination of diclofenac concentrations in human plasma

We have modified and validated a capillary GC-MS method reported by Kadowaki et al. [J. Chromatogr., 308 (1984) 329] for the determination of diclofenac in human plasma by using heptane rather than benzene as an extraction agent. In addition, acetone was added to the samples as a deproteination agent which increased the recovery of diclofenac. These revised processes allowed clean extraction and near-quantitative recovery of analyte (> 95%). Separation was achieved on an HP-1 column with helium as carrier gas. The parent ion peaks of diclofenac (m/z 277) and the internal standard, 4'-methoxydiclofenac (m/z 307), were monitored by a mass-selective detector using the selected-ion monitoring mode. The linear range for the routine assay was from 5 to 2000 ng/ml. The detection and lower quantifiable limits were 0.2 and 1 ng/ml, respectively, with no interference from plasma. The within-day and between-day coefficients of variation for high and medium concentrations were less than 5% and were less than 13% for low concentrations (10 ng/ml). This GC-MS assay method has been used for pharmacokinetic and drug interaction studies in humans.

Pharmacokinetics of ketoprofen in the donkey (Equus asinus)

The pharmacokinetic parameters of ketoprofen were determined in four donkeys after a single intravenous injection of a dose of 2.2 mg/kg body weight. The total body clearance (ClB) was 414.0 +/- 98.70 ml/h/kg (mean +/- SD), the volume of distribution at steady state (Vss) 263.10 +/- 55.43 ml/kg and the elimination half-life 1.30 +/- 0.75 h. These values were compared to those obtained in horses.

Rapid screening for acidic non-steroidal anti-inflammatory drugs in urine by gas chromatography-mass spectrometry in the selected-ion monitoring mode

A rapid screening procedure is described for the simultaneous determination of various acidic non-steroidal anti-inflammatory drugs (NSAIDs) at sub-nanogram levels. The procedure involves solid-phase extraction (SPE) of NSAIDs using Chromosorb P as the adsorbent in partition mode, with subsequent single-step conversion to tert-butyldimethylsilyl (TBDMS) derivatives, followed by direct analysis by gas chromatography-mass spectrometry (GC-MS). The characteristic [M-57]+ high-mass ions constituting the base peaks in the electron-impact mass spectra of most TBDMS derivatives permitted sensitive detection of NSAIDs by GC-MS in selected-ion monitoring (SIM) mode, even in the presence of higher levels of coextracted urinary organic acids. The detection limit for SIM of each drug was in the range 0.03-0.9 pg. When applied to urine samples (250 microliters) spiked with NSAIDs, the present GC-SIM-MS method allowed simultaneous screening for various NSAIDs with good overall precision and accuracy in the range of 10-40 ng.

Detection of non-steroidal anti-inflammatory drugs in equine plasma and urine by gas chromatography-mass spectrometry

A gas chromatographic-mass spectrometric (GC-MS) procedure for the detection of seventeen non-steroidal anti-inflammatory drugs (NSAIDs) in equine plasma and urine samples is described. The extraction of the compounds from the biological matrix was performed at acidic pH (2-3) with diethyl ether. Ethereal extracts were washed with a saturated solution of sodium hydrogencarbonate (urine) or treated with a solid mixture of sodium carbonate and sodium hydrogencarbonate (plasma). The ethereal extracts were dried and derivatized by incubation at 60 degrees C with methyl iodide in acetone in the presence of solid potassium carbonate. Mono- or bismethyl derivatives of the NSAIDs were obtained. After derivatization kinetic studies, 90 min was the incubation time finally chosen for screening purposes for adequate methylation of all the compounds under study. For individual confirmation analyses, shorter incubation times can be used. The chromatographic analysis of the derivatives was accomplished by GC-MS with a run time of 13 min. In general, extraction recoveries ranged from 23.3 to 100% in plasma and from 37.5 to 83.8% in urine samples. Detection limits from less than 5 to 25 ng/ml were obtained for both plasma and urine samples using selected-ion monitoring. The procedure was applied to the screening and confirmation of NSAIDs in routine doping control of equine samples.

Percutaneous absorption of salicylates from some commercially available topical products containing methyl salicylate or salicylate salts in rats

Studies to determine the extent of local tissue penetration of topically applied, commercially available salicylate esters and salts were conducted in male Wistar rats. The salicylate concentration in plasma, tissues underlying the site of drug application, and similar tissues on the contralateral (control) side were measured. The plasma and tissue salicylate levels suggest that direct penetration of salicylate was predominant to the top muscle level on the treated site. Results also suggest that the drugs were first absorbed into the bloodstream and subsequently distributed to both the deeper tissues on the treated site and the contralateral tissues. The topical application of formulations of ester methyl salicylate and salts triethanolamine salicylate and diethylamine salicylate containing comparable salicylate concentrations yielded similar salicylate concentrations in the various tissues. The salicylate concentrations in the deeper tissues approached concentrations observed in the contralateral tissues suggesting that salicylate present in these tissues was due to the systemic blood supply.

Determination of ibuprofen in erythrocytes and plasma by high performance liquid chromatography

A high-performance liquid chromatographic (HPLC) method is described for the determination of ibuprofen in isolated erythrocytes and plasma. Before HPLC analysis ibuprofen was isolated by liquid-liquid extraction from these biological matrices; methylene chloride proved to be the best of the organic solvents tested. For the sample of erythrocytes it was necessary to carry out haemolysis prior to their extraction. HPLC was performed on a C-18 column with a mobile phase of methanol-water (220:100, v/v) acidified with perchloric acid to pH 3. Ultraviolet detection was at 222 nm. This method has been applied to the quantification of ibuprofen in rabbit erythrocytes and plasma for a pharmacokinetics study.

Disappearance kinetics of solutes from synovial fluid after intra-articular injection

1. Five rheumatoid patients with a knee joint effusion participated in the study. An aqueous solution (0.1 to 0.2 ml) containing paracetamol, salicylate, diclofenac and [125I]-albumin was injected into a given joint to yield target concentrations of approximately 20 micrograms ml-1 for diclofenac, salicylate and paracetamol and 10(8) counts ml-1 for [125I]-albumin. 2. Paracetamol, salicylate and diclofenac were analysed in synovial fluid by h.p.l.c. [125I]-albumin was analysed using gamma counting. 3. The clearances (+/- s.d.) obtained for the solutes were [125I]-albumin (0.0053 +/- 0.0019 l h-1), diclofenac (0.0096 +/- 0.0061 l h-1), salicylate (0.024 +/- 0.022 l h-1) and paracetamol (0.055 +/- 0.041 l h-1). The corresponding fractions unbound of these solutes in synovial fluid were 0.0, < or = 0.01, 0.34 +/- 0.09 and 0.85 +/- 0.10, respectively. 4. Diffusion of unbound solute through the synovium is estimated to account for (+/- s.d.) 0.52 +/- 0.08, 0.87 +/- 0.06 and 0.99 +/- 0.01 of the total clearance of diclofenac, salicylate and paracetamol from the joint space, respectively. The remaining proportion of clearance is accounted for by efflux of solute bound to albumin. 5. An expression for the ratio of synovial fluid to total plasma concentrations after systemic administration was developed to include both diffusion of unbound solute and albumin flux. Most solutes appear to satisfy the conditions in which this expression reduces to the limiting case where the unbound concentration of the solute is identical in the synovial fluid and plasma under steady state conditions.

High-performance liquid chromatographic assay for ibuprofen in whole blood using solid-phase extraction

A precise, accurate, reproducible one-step method for the high-performance chromatographic determination of ibuprofen in whole blood is described. Samples were, after haemolysis, prepared by solid-phase extraction. Analyses were performed using reversed-phase chromatography on a Separon SGX C18 column with a mobile phase of methanol-water (pH 3) and ultraviolet detection at 222 nm. The method was used for pharmacokinetic studies in rabbits.

Dermal and underlying tissue pharmacokinetics of salicylic acid after topical application

The time course of salicylic acid at a dermal application site and in local underlying tissues below the site in rats was examined using a physiologically based pharmacokinetic model assuming first-order diffusional mass transfer between the dermis and underlying tissues. The concentrations of salicylic acid in tissues below the applied site were measured and compared with plasma concentrations and concentrations in similar tissues on the contralateral side. The direct penetration of salicylic acid was dominant only to a depth of 3-4 mm below the applied site for the first approximately 2 hr after application. The time course of salicylic acid in individual rats was modeled using known tissue blood flows and tissue-tissue clearances by (i) numerical integration and nonlinear regression of a series of differential equations representing events in individual tissues, and (ii) numerical integration and nonlinear regression of a single differential equation representation of the concentration-time course in an individual tissue with a polynomial representation of salicylate concentrations in other input tissues and an exponential representation of the input from the solution. Tissue-tissue clearances were deduced by both nonlinear regression and mass balance analysis (only for underlying dermis) using area-under-the-curves from salicylic acid tissue penetration data in anesthetized rats. The relative importance of direct penetration and blood supply in determining the concentrations of salicylic acid in deeper tissues was assessed by simulations in which either no direct penetration occurred or there was zero input from blood. Simulations confirm that direct penetration is only evident in the superficial tissues for approximately 2 hr. An attempt was also made to examine the dermal pharmacokinetics of salicylic acid using statistical moments.

Enantiospecific gas chromatographic-mass spectrometric procedure for the determination of ketoprofen and ibuprofen in synovial fluid and plasma: application to protein binding studies

A method for the enantiospecific quantitation of two commonly prescribed non-steroidal anti-inflammatory drugs (ketoprofen and ibuprofen) is described. The method involves formation of a mixed anhydride of the drug with ethylchloroformate and subsequent conversion to an amide by reaction with optically active amphetamine. The subsequently formed diastereomers are separated by gas chromatography-mass spectrometry using selected-ion monitoring. The assay is capable of quantifying ketoprofen (2 ng/ml) and ibuprofen (3 ng/ml) enantiomers from a 200-microliters sample of synovial fluid or plasma and is particularly suitable for protein binding studies.

Bioanalysis of diclofenac as its fluorescent carbazole acetic acid derivative by a post-column photoderivatization high-performance liquid chromatographic method

A sensitive and selective bioanalytical liquid chromatographic method for diclofenac is described. The drug was detected as a flourescent derivative, which was demonstrated by 1H NMR and mass spectrometric studies to be carbazole acetic acid. Diclofenac was derivatized by UV irradiation of the substance performed as a post-column photoreaction. The reactor was a PTFE capillary wound around a 254-nm UV lamp. Diclofenac was isolated from the plasma samples by precipitation of the proteins with acetonitrile. A 50-microliters volume of the supernatant was injected onto a Nucleosil C18 column. The mobile phase was 32% acetonitrile in pH 6.6 buffer. Carbazole acetic acid was detected by a fluorescence detector using an excitation wavelength of 288 nm and an emission wavelength of 360 nm. The recovery was 92%, the standard curve was linear in the range 10-5500 ng diclofenac per ml plasma, and the relative standard deviation at 10 and 5000 ng of diclofenac per ml plasma was 9.0% and 3.3%, respectively. The limit of detection was 6 ng/ml at an injection volume of 50 microliters. Chromatograms of human and rat plasma containing diclofenac are shown.

Ibuprofen inhibits localized bone resorption in the middle ear

Localized osteoclastic bone resorption plays a significant role in the pathogenesis of several diseases of the middle ear as well as orthodontic tooth movement and long bone remodeling. The mechanisms of control of localized bone loss and systemic bone resorption may be different but both may be mediated by a final common pathway which includes prostaglandins. Prostaglandins seem to have a predominantly stimulatory effect on bone resorption, although the exact mechanism is poorly understood. Ibuprofen, a nonsteroidal antiinflammatory drug, is known to inhibit the synthesis of prostaglandins. It is likely that ibuprofen, through its inhibition of prostaglandin synthesis, would decrease the localized osteoclastic bone resorption in a previously described animal model system. Mongolian gerbils were divided into three groups: low dose ibuprofen (10 mg/kg per day), high dose ibuprofen (30 mg/kg per day), and a control group. Following surgical implantation of catheters to the right bullae of each gerbil, pressure was applied for 8 days, stimulating osteoclastic bone resorption. After killing the animals and histomorphometric analysis of the bullae from each, comparisons were made between each group using osteoclast surface (percentage of bone area covered by osteoclasts), osteoclast number (number of osteoclasts/mm bone length), and osteoclast profile area (in microns2). Significantly lower osteoclast surface (Oc.S/BS) was found in pressurized bullae from both treatment groups when compared with pressurized bullae from controls (P less than 0.05) and significantly lower osteoclast number (N.Oc/T.L) in pressurized bullae from both treatment groups when compared with pressurized bullae from controls (P less than 0.05). These differences were found to be dose-dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

Spectrophotometric determination of diclofenac sodium in tablets

Simple spectrophotometric methods are described for the determination of diclofenac. In the first method diclofenac reduces iron(III) to iron(II) when heated in aqueous solution. The ferrous ions produced react with 2,2'-bipyridine to form a complex having a maximum absorbance at 520 nm. The reaction obeys Beer's Law for concentrations of 10-80 micrograms ml-1. This method can be applied to the determination of diclofenac in tablets. In the second method, diclofenac is treated with Methylene Blue in the presence of phosphate buffer (pH 6.8) and the complex is extracted with chloroform. The complex has a maximum absorbance at 640 nm and the graph of absorbance against concentration is linear in the range 5-40 micrograms ml-1. This method can be applied to the determination of diclofenac in tablets that also contain paracetamol.

Liquid chromatography with amperometric detection for the determination of non-steroidal anti-inflammatory drugs in plasma

A simple and sensitive liquid chromatographic method with electrochemical detection is described for the quantitative determination of the non-steroidal anti-inflammatory drugs diflunisal, indomethacin, naproxen, piroxicam and sulindac in human plasma. Isolation of the drug from the biological fluid is achieved using a Sep-pak RP18 cartridge. Separation of plasma components occurs on a reversed-phase C18 column with a mobile phase consisting of methanol-water-phosphate buffer. For the amperometric detection the potential of +0.9 V was set on the working electrode. The detection limit of the assay is 10-20 ng/ml. The method showed good concordance for plasma samples containing the drugs (r = 0.999) and can be readily utilized for clinical pharmacokinetic studies.

Identification and simultaneous determination of non-steroidal anti-inflammatory drugs using high-performance liquid chromatography

An isocratic high-performance liquid chromatographic procedure is presented for the screening of plasma samples for the presence of sixteen non-steroidal anti-inflammatory drugs. Detection was achieved simultaneously at two wavelengths (254 and 370 nm) and the purity of the eluted peaks was tested using absorbance ratios at the two wavelengths; identification could thus be effective without interferences from substances of other pharmacological classes. The drugs were extracted simultaneously with diethyl ether after acidification and separated from each other on an octadecyl reversed-phase column using only one eluent, acetonitrile-0.3% acetic acid-tetrahydrofuran (36:63.1:0.9, v/v). The recovery, precision and reproducibility of the method were satisfactory as it allowed the determination of the drugs from infra- to supratherapeutic concentrations.

High performance liquid chromatographic determination of diclofenac sodium in plasma using column-switching technique for sample clean-up

For routine analysis of diclofenac sodium in plasma, a new high performance liquid chromatographic method, which is combined with column-switching technique is developed. The precolumn packed with Corasil RP C-18 was connected to analytical column by switching system in order to enrich the sample drugs in plasma without extraction. This method showed excellent sensitivity, precision and reproducibility. The limit of detection, using a 100 microL injection of plasma, was 0.1 micrograms/mL and the mean coefficient of variation for intra- and inter-assay was better than 4.6%. Total analysis time was 20 min between injections. The present method offers distinct practical advantages over conventional liquid-liquid extraction methods of sample preparation with respect to time, effort, recovery, and sample volume required. The method has been applied to the samples from rats receiving oral administration of diclofenac sodium.

The determination of non-steroidal anti-inflammatory drugs by GC-MS-MS in equine urine

Results are given for a more sensitive screening procedure for non-steroidal anti-inflammatory drugs using GC-MS-MS. By monitoring a selected characteristic reaction for each drug very low detection limits are reached even in a difficult biological matrix such as equine urine. Detection down to 5 ng ml-1 for ibuprofen, ibufenac, alclofenac, fenoprofen, ketoprofen, naproxen and diclofenac is possible in contrast to the 0.5 microgram ml-1 limit for normal GC-MS detection. Examples are given of real positive cases for diclofenac and ibuprofen.