Concentrations of indomethacin and its metabolite desmethylindomethacin in plasma and urine after repeated indomethacin topical application to Thoroughbreds.

BACKGROUND: Repeated topical application of indomethacin is common in Japanese racehorses, despite the lack of pharmacokinetic data. OBJECTIVES: To determine the concentrations of indomethacin and its metabolite, desmethylindomethacin, in plasma and urine of Thoroughbreds topically treated repeatedly with indomethacin. STUDY DESIGN: In vivo experimental. METHODS: Seven female Thoroughbreds were topically treated with 50 g of 1% indomethacin cream per horse to the back and hips (500 mg of indomethacin/head/2400 cm2 , 0.21 g/cm2 ) for 3 consecutive days. Samples were pretreated by protein precipitation for plasma and liquid-liquid extraction with ethyl acetate after hydrolysis with hydrochloric acid for urine. The concentrations of indomethacin and desmethylindomethacin in plasma and urine were measured by liquid chromatography-mass spectrometry. RESULTS: Indomethacin was quantifiable in plasma up to 48-72 h and in urine up to 96 h after the final application. Desmethylindomethacin was quantifiable in plasma up to 48 h and in urine up to 72-96 h after the final application. MAIN LIMITATIONS: The relationship between the local and systemic indomethacin concentrations after the topical application was not clarified. CONCLUSIONS: Pharmacokinetic data were acquired for repeated topical administration of 1% indomethacin cream to Thoroughbreds. Hydrolysing urine samples with hydrochloric acid was effective for the analysis of indomethacin and its metabolite, and indomethacin may be an excellent marker analyte for doping tests. The estimated withdrawal time based on the limit of detection was 342 h.

Development of a novel 96-well format for liquid-liquid microextraction and its application in the HPLC analysis of biological samples.

A novel 96-well liquid-liquid microextraction system combined with modern HPLC was developed and used for the simultaneous analysis of 96 biological samples. The system made use of hollow fibers, a 96-well plate, and a plastic base with a center hole and a side hole. One end of the hollow fiber was sealed, while the other end was attached to one of the holes positioned at the center for the plastic base. The needle was inserted into the liquid from inside or outside of the hollow fiber through the center or the side holes, respectively. The system was tested with plasma samples containing three compounds, acidic indomethacin, neutral dexamethasone, and basic propafenone. Some parameters, such as the kind and dimension of hollow fiber, pH and salt concentration of the donor phase, the selection of organic solvent for the acceptor phase, and the extraction time were investigated. Under the optimization conditions, the Log D and drug concentration of indomethacin, dexamethasone, and propafenone in plasma and urine samples were analyzed. Then, the methodology was validated. The results demonstrated that ng/mL levels could be exactly and rapidly analyzed by our system, which was equipped with an auto-injection sampler, making sample analysis more convenient.

A liquid chromatography method with single quadrupole mass spectrometry for quantitative determination of indomethacin in maternal plasma and urine of pregnant patients.

A liquid chromatography with single quadrupole mass spectrometry method was developed for the quantitative determination of indomethacin in the maternal plasma and urine of pregnant patients under treatment. A deuterium-labeled isotope of indomethacin (d4-indomethacin) was used as an internal standard. The maternal plasma and urine samples were acidified with 1.0M HCl then extracted with chloroform to achieve the extraction recovery range of 94-104% with variation less than 11%. Chromatographic separation was achieved by a Waters Symmetry C18 column with isocratic elution of 0.05% (v/v) formic acid aqueous solution and acetonitrile (47:53, v/v). An in-source fragmentation was applied on the single quadrupole mass spectrometer equipped with an electrospray ionization source at positive mode. The LC-ESI-MS quantification was performed in the selected ion monitoring mode targeting ions at m/z 139 for indomethacin and m/z 143 for its internal standard. The calibration curves were linear in the concentration ranges between 14.8 and 2.97 × 10(3) ng/mL for plasma samples and between 10.5 and 4.21 × 10(3) ng/mL for urine samples. The relative standard deviation of this method was less than 8% for intra- and inter-day assays, and the accuracy ranged between 90% and 108%.

Determination of non-steroidal anti-inflammatory drugs in urine by the combination of stir membrane liquid-liquid-liquid microextraction and liquid chromatography.

A stir membrane liquid phase microextraction procedure working under the three-phase mode is proposed for the first time for the determination of six anti-inflammatory drugs in human urine. The target compounds are isolated and preconcentrated using a special device that integrates the extractant and the stirring element. An alkaline aqueous solution is used as extractant phase while 1-octanol is selected as supported liquid membrane solvent. After the extraction, all the analytes are determined by liquid chromatography (LC) with ultraviolet detection (UV). The analytical method is optimized considering the main involved variables (e.g., pH of donor and acceptor phases, extraction time, stirring rate) and the results indicate that the determination of anti-inflammatory drugs at therapeutic and toxic levels is completely feasible. The limits of detection are in the range from 12.6 (indomethacin) to 30.7 µg/L (naproxen). The repeatability of the method, expressed as relative standard deviation (RSD, n = 5) varies between 3.4% (flurbiprofen) and 5.7% (ketoprofen), while the enrichment factors are in the range from 35.0 (naproxen) to 72.5 (indomethacin).

Determination of methotrexate and indomethacin in urine using SPE-LC-DAD after derivatization.

A validated HPLC-DAD assay is presented for the simultaneous quantification of methotrexate and indomethacin in a drug combination which is used synergistically to intervene with tumoral or inflammatory tissue microenvironments. The analytes were isolated from urine via solid phase extraction. The method is based on derivatizing both analytes with a soluble carbodiimide coupler and 2-nitrophenylhydrazine directed to their commonly occurring carboxylate functions. The chromatographic separation was accomplished on an octylsilica column in less than 15 min using acetate buffer (pH 4; 10 mM)-methanol (60:40, v/v) as eluent at 1.5 ml/min and monitored at 400 nm. The selectivity of the method was demonstrated in a pre-dosed rheumatoid arthritis patient. Quality control samples were prepared and analyzed to reveal the validity of the method. Life samples collected from a healthy volunteer were monitored for both drugs and their urinary levels were determined.

Sensitive determination of indomethacin in pharmaceuticals and urine by sequential injection analysis and optosensing.

A selective and sensitive method based on coupling of sequential injection analysis (SIA) and optosensing was developed and applied to the determination of indomethacin in pharmaceutical and urinary samples. After alkaline hydrolysis, the fluorescent product generated from indomethacin is inserted in the flow system, transitorily retained on an active solid support (Sephadex QAE A-25) filling the flowcell, and monitored at 283/371 nm (lamda ex / lamda em). The system was calibrated for two sample volumes, 100 and 1000 microL. It showed a linear dynamic range of 0.5-6.5 ng/mL, with an LOD of 0.15 ng/mL and an RSD of 3.9% (n=10) when the highest sample volume was used. The proposed fluorometric SIA optosensor was applied to the determination of indomethacin in both pharmaceuticals and urine samples, and satisfactory results were obtained.

[Tissue distribution and excretion of 5-fluorouracil from indomethacin 5-fluorouracil-1-ylmethylester in rats].

To study the tissue distribution and excretion of indomethacin 5-fluorouracil-1-ylmethyl ester (IFM) metabolite 5-fluorouracil in rats, an accurate and specific high performance liquid chromatography method for quantifying IFM in rat plasma and tissues was developed. Biological samples were prepared by liquid-liquid extraction and separated on a Diamonsil C18 column (250 mm x 4.6 mm ID, 5 microm). The mobile phase for tissue samples, plasma samples and feces samples were composed of methanol-water-36% acetic acid (3:96.9:0.1, v/v) and the mobile phase for urine samples was a mixture of methanol-water-36% acetic acid (10:89.9:0.1, v/v). The eluate was monitored by UV absorbance at 260 nm. After a single ig dose of 100 mg x kg(-1) IFM in rats, 5-Fu was mainly distributed in stomach, small intestine, and liver. The concentrations of 5-fluorouracil in other tissues and plasma were low. The excretion of 5-Fu in urine and feces amounted to 0.0065% and 0.063% of the dose, respectively. The method is shown to be accurate and specific, and suitable for preclinical pharmacokinetic studies of IFM.

Determination of non-steroidal anti-inflammatory drugs in urine by combining an immobilized carboxylated carbon nanotubes minicolumn for solid-phase extraction with capillary electrophoresis-mass spectrometry.

Last years, the usefulness of the use of carbon nanotubes (CNTs) as sorbent material have been demonstrated for a wide variety of compounds. In this work, it has been demonstrated for first time that immobilized carboxylated single-walled carbon nanotubes (c-SWNTs) offer clear advantages over the use of CNTs. The higher adsorption capacity has been attributed to the special orientation of c-SWNTs molecules on the glass surface. The potential of this new sorbent was evaluated for the preconcentration of non-steroidal anti-inflammatory drugs (NSAIDs) from urine samples. Purified samples were analysed by capillary electrophoresis-mass spectrometry detection allowing the determination of 1.6 to 2.6 microg/L of NSAIDs with only 5 mL of sample. The precision of the method for the determination of real spiked urine samples ranged from 5.4 to 7.4% and the recoveries from 98.6 to 102.2%.

Clearance and disposition of indometacin in chronically instrumented fetal lambs following a 3-day continuous intravenous infusion.

Indometacin is used in pregnancy for the treatment of premature labour, but there are limited data on the disposition of the drug in the fetus. In order to elucidate fetal indometacin pharmacokinetics at plasma levels and duration comparable with those occurring with use of the drug for tocolysis in humans, indometacin was administered at doses of 1.9 (low dose, LD; n = 5) or 7.5 (high dose, HD; n = 9) microg min(-1) to steady state over a 3-day period in chronically instrumented fetal lambs. Indometacin concentrations in biological fluid samples were analysed by a sensitive capillary gas chromatography-electron capture detection method. The mean steady-state fetal arterial plasma indometacin concentrations were 68.6+/-16.5 ng mL(-1) in the LD infusion and 230.3+/-28.8 ng mL(-1) in the HD infusion. Indometacin concentrations in amniotic fluid were approximately 10% of those in fetal plasma, and below assay detection limits in tracheal fluid. Total body clearance (TBC) in the LD and HD infusions were not different and the overall mean was 11.3+/-1.2 mL min(-1) kg(-1). In the 11 experiments where paired fetal arterial and umbilical venous samples were collected, the extraction of indometacin across the placenta averaged only 5.2+/-1.1%, indicating low placental permeability to the drug in sheep. However, fetal placental clearance (CLpl) of indometacin (10.0+/-2.5 mL min(-1) kg(-1), n = 10) averaged 115.1+/-41.2% of TBC in these animals and the calculated value for fetal non-placental clearance (0.6+/-2.8 mL min(-1) kg(-1)) was not significantly different from zero. Fetal renal clearance of intact indometacin (3.8+/-1.1 microL min(-1) kg(-1); n = 12) was also very low. However, treatment of fetal urine with glucuronidase indicated the presence of glucuronide conjugates and these comprised 69.9+/-8.2% of the total drug concentration (i.e. intact+conjugated) in urine. Thus, the fetal lamb appears to be able to glucuronidate indometacin, but the contribution of this and other non-placental routes to overall fetal elimination of the drug appear minimal. CLpl of the drug is also low owing to the physicochemical properties of indometacin (high polarity) and the permeability characteristics of the sheep placenta.

Determination of nonsteroidal anti-inflammatory drugs in biological fluids by automatic on-line integration of solid-phase extraction and capillary electrophoresis.

A new, automatic method for the clean-up, preconcentration, separation, and quantitation of nonsteroidal anti-inflammatory drugs (NSAIDs) in biological samples (human urine and serum) using solid-phase extraction coupled on-line to capillary electrophoresis is proposed. Automatic pretreatment is carried out by using a continuous flow system operating simultaneously with the capillary electrophoresis equipment, to which it is linked via a laboratory-made mechanical arm. This integrated system is controlled by an electronic interface governed via a program developed in GWBasic. Capillary electrophoresis is conducted by using a separation buffer consisting of 20 mM NaHPO4, 20 mM beta-cyclodextrin and 50 mM SDS at pH 9.0, an applied potential of 20 kV and a temperature of 20 degrees C. The analysis time is 10 min and the detection limits were between 0.88 and 1.71 microg mL(-1). Automatic clean-up and preconcentration is accomplished by using a C-18 minicolumn and 75% methanol as eluent. The limit of detection of NSAIDs can be up to 400-fold improved when using sample clean-up. The extraction efficiency for these compounds is between 71.1 and 109.7 microg mL(-1) (RSD 2.0-7.7%) for urine samples and from 77.2 to 107.1 microg mL(-1) (RSD 3.5-7.1%) for serum samples.

Study of the solid-phase extraction of diclofenac sodium, indomethacin and phenylbutazone for their analysis in human urine by liquid chromatography.

A selective semi-automated solid-phase extraction (SPE) of the non-steroidal anti-inflammatory drugs diclofenac sodium, indomethacin and phenylbutazone from urine prior to high-performance liquid chromatography was investigated. The drugs were recovered from urine buffered at pH 5.0 using C18 Bond-Elut cartridges as solid sorbent material and mixtures of methanol-aqueous buffer or acetonitrile-aqueous buffer as washing and elution solvents. The extracts were chromatographed on a reversed-phase ODS column using 10 mM acetate buffer (pH 4.0)-acetonitrile (58:42, v/v) as the mobile phase, and the effluent from the column was monitored at 210 nm with ultraviolet detection. Absolute recoveries of the anti-inflammatory drugs within the range 0.02-1.0 microg/ml were about 85% for diclofenac and indomethacin, and 50% for phenylbutazone without any interference from endogenous compounds of the urine. The within-day and between-day repeatabilities were in all cases less than 5% and 10%, respectively. Limits of detection were 0.007 microg/ml for diclofenac sodium and indomethacin and 0.035 microg/ml for phenylbutazone, whereas limits of quantitation were 0.02 microg/ml for diclofenac and indomethacin and 0.1 microg/ml for phenylbutazone.

Cathodic adsorptive stripping voltammetric determination of the anti-inflammatory drug indomethacin.

Sensitive voltammetric methods have been developed for the determination of the anti-inflammatory, anti-pyretic and analgesic drug indomethacin sodium. The methods are based on the controlled adsorptive preconcentration of the drug on a hanging mercury drop electrode (HMDE), followed by tracing the voltammogram in a cathodic potential scan. The modes used are cyclic voltammetry (CV), cathodic stripping voltammetry (CSV) and differential pulse stripping voltammetry (DPSV). Amounts as low as 10 nM (10 ng x ml(-1)) (60 s preconcentration) by CSV and 0.5 microM (190 ng x ml(-1)) (300 s) by DPSV can be determined accurately. The R.S.D. at the 1 x 10(-6) M level is 1.4%. The interference of some metal ions and the application of the method to analysis of urine, plasma and pharmaceutical formulations are described.

Sensitive fused-silica capillary gas chromatographic assay using electron-capture detection for indomethacin in ovine fetal fluids.

A sensitive gas chromatographic (GC) method with electron-capture detection (ECD) has been developed to quantitate indomethacin (IND) in plasma, urine, amniotic, and tracheal fluids obtained from the pregnant sheep model. IND and the internal standard, alpha-methylindomethacin (alpha-Me-IND) are extracted by a simple liquid-liquid extraction procedure using ethyl acetate and derivatized with N-methyl-N-(tert.-butyldimethyl-silyl)trifluoroacetamide (MTBSTFA) at 60 degrees C for 50 min. The limit of quantitation (LOQ) is 1 ng/ml with a C.V. < 10% and signal-to-noise ratio > 10. Recoveries from all fluids were greater than 80%. Calibration curves were linear over the range of 1-32 ng/ml with a coefficient of determination (r2) > 0.999. Inter- and intra-day coefficients of variation were < 10% at concentrations of 2-32 ng/ml, and < 20% at the LOQ. Applicability of the developed method is demonstrated for a pharmacokinetic study of IND samples collected following long-term infusion of IND in a chronically instrumented ovine fetus.

Probenecid inhibits the glucuronidation of indomethacin and O-desmethylindomethacin in humans. A pilot experiment.

Indomethacin is metabolized in humans by O-demethylation, and by acyl glucuronidation to the 1-O-glucuronide. Indomethacin, its metabolite, and their conjugates can be measured directly by gradient high-pressure liquid chromatographic analysis without enzymic deglucuronidation. The pharmacokinetic profile of indomethacin and some preliminary pharmacokinetic parameters of indomethacin obtained from one human volunteer are given. In plasma only the parent drug indomethacin is present, while in urine the acyl and ether glucuronides are present in high concentrations. This confirms other reports that indomethacin and O-desmethylindomethacin may be glucuronidated in the kidney. Probenecid is a known substrate for renal glucuronidation. If indomethacin is glucuronidated in the human kidney like probenecid, then this glucuronidation might be reduced or inhibited under probenecid co-medication. This pilot experiment shows that probenecid reduced the acyl glucuronidation of indomethacin by 50% and completely inhibited the formation of O-desmethylindomethacin acyl and ether glucuronide.

Further evaluation of a new penetration enhancer, HPE-101.

The penetration enhancer, 1-[2-(decylthio)ethyl]azacyclopentan-2-one (HPE-101), significantly enhanced the excretion of topically applied [14C]indomethacin when dissolved in dipropylene glycol, triethylene glycol, diethylene glycol, 1,3-butylene glycol, trimethylene glycol, glycerin, water, silicone or triethanolamine, but not when dissolved in ethanol, isopropyl alcohol, oleyl alcohol, olive oil, peppermint oil, isopropyl myristate or hexylene glycol. HPE-101 significantly enhanced the excrection of [14C]indomethacin, [14C]nicotinic acid, [14C]5-fluorouracil, [3H]oestradiol and [3H]triamcinolone acetonide, but not that of [3H]testosterone. HPE-101 also significantly enhanced the excretion of [14C]indomethacin applied to intact skin of rabbit, guinea-pig and rat, and to tape-stripped skin of guinea-pig, but did not enhance the excretion of [14C]indomethacin applied to tape-stripped skin of rat or rabbit.

Determination of indomethacin, its metabolites and their glucuronides in human plasma and urine by means of direct gradient high-performance liquid chromatographic analysis. Preliminary pharmacokinetics and effect of probenecid.

Indomethacin is metabolized in humans by O-demethylation, and by acyl glucuronidation to the 1-O-glucuronide. Indomethacin, its metabolite O-desmethylindomethacin (DMI) and their conjugates can be measured directly by gradient high-performance liquid chromatographic analysis without enzymic deglucuronidation. The glucuronide conjugates were isolated by preparative HPLC from human urine samples. In plasma only indomethacin was present. No isoglucuronides were present in acidic urine of the volunteer. The possible metabolite deschlorobenzoylindomethacin (DBI) was not detectable in urine. Calibration curves were constructed by enzymic deconjugation of samples containing different concentrations of isolated indomethacin acyl glucuronide, DMI acyl glucuronide and DMI ether glucuronide. The limit of quantitation of indomethacin in plasma is 0.060 microgram/ml. The limits of quantitation in urine are: indomethacin 0.053 microgram/ml, DMI 0.065 microgram/ml, DMI acyl glucuronide 0.065 microgram/ml and DMI ether glucuronide 0.254 microgram/ml. A pharmacokinetic profile of indomethacin is shown, and some preliminary pharmacokinetic parameters of indomethacin obtained from one human volunteer are given. Probenecid inhibits the formation of both the ether and the acyl glucuronide of DMI.

Evaluation of a new penetration enhancer 1-[2-(decylthio)ethyl]azacyclopentan-2-one (HPE-101).

A new compound, 1-[2-(decylthio)ethyl]azacyclopentan-2-one (HPE-101) was synthesized, and its skin penetration enhancing activity was examined by using 14C-indomethacin as a penetrant. A solution of HPE-101 and indomethacin was applied to a cloth pad affixed onto an adhesive tape to give a HPE-101 patch, and the patch was applied to hairless mouse skin. The amount of percutaneously absorbed indomethacin was determined by measuring the radioactivity excreted in urine for 24 h after application. 1) Azone and decylmethyl sulfoxide, enhanced markedly the percutaneous absorption of indomethacin when the propylene glycol-ethanol (9:1 v/v) mixture was used as the solvent. 2) Among various penetration enhancers dissolved in the indomethacin solutions and applied to screen for penetration enhancing activity, HPE-101 was found to be the most prominent. 3) Solvents containing more than 3% (w/w) of HPE-101 produced a plateau level of the penetration enhancing activity. 4) Daily application of 1% (w/w) solutions of HPE-101 or Azone increased the daily excretion of indomethacin significantly above the level excreted on the previous day. However, repeated daily application beyond 3 d gave a steady state excretion of indomethacin. 5) The mouse skin was pretreated with 3% (w/w) solutions of HPE-101 or Azone for 24 h on the 1st day, and the indomethacin solution was applied for 24 h on the 3rd day and 7th day to examine the recovery of skin barrier function. Enhanced excretion of indomethacin was still noted on the 3rd day, but enhancement was not observed on the 7th day.

Clearance of indomethacin occurs predominantly by renal glucuronidation.

In this report we describe the conditions of collection, storage and handling of urine samples, collected after oral dosing with indomethacin in man, in order to maintain the integrity of the labile glucuronide formed. We found that the body clearance occurs predominantly by renal metabolism, due to glucuronidation in the human kidney. These glucuronides may be converted to isomeric glucuronides and/or the parent compound indomethacin during the residence time in the bladder.

Simultaneous analysis of flunixin, naproxen, ethacrynic acid, indomethacin, phenylbutazone, mefenamic acid and thiosalicylic acid in plasma and urine by high-performance liquid chromatography and gas chromatography-mass spectrometry.

Simple and reproducible high-performance liquid chromatographic (HPLC) and gas chromatographic-mass spectrometric (GC-MS) methods have been developed for the simultaneous analysis of several acidic drugs in horse plasma and urine. Although the capillary GC-MS column provided better separation of the drugs than the reversed-phase C8 (3 microns, 75 mm) HPLC column, the total analysis time with HPLC was shorter than the total analysis time with GC-MS. The HPLC system equipped with a diode-array detector provided simultaneous screening (limit of detection 100-500 ng/ml) and confirmation (limit 1.0 micrograms/ml) of the drugs. The HPLC system equipped with fixed-wavelength ultraviolet and fluorescence detectors provided a relatively sensitive screening [limit of detection 50-150 ng/ml for ultraviolet and 10 ng/ml for fluorescence (naproxen only) detectors] of the drugs. However, the positive samples had to be confirmed by using either the diode-array detector or the GC-MS system. The GC-MS system provided simultaneous screening and confirmation of the drugs at very low concentrations (20-50 ng/ml).