Improved method for the determination of indomethacin in plasma and urine by reversed-phase high-performance liquid chromatography

Square-wave adsorptive cathodic stripping voltammetric determination of anti-inflammatory indomethacin drug in tablets and human serum at a mercury electrode

Indomethacin is a non-steroidal anti-inflammatory drug possessing anti-pyretic and analgesic properties. A fully validated square-wave adsorptive cathodic stripping voltammetric procedure is described for determination of indomethacin. The procedure was based on the reduction of the C=O double bond of the drug molecule in Britton-Robinson buffer (pH 4) after its preconcentration onto the mercury electrode surface. The optimized conditions of the procedure were: frequency 120 Hz, scan increment 10 mV, pulse amplitude 50 mV, preconcentration potential -0.9 V (vs. Ag/AgCl/KCl(s)) and preconcentration time 90 s. The proposed procedure was successfully applied for determination of the drug in tablets and human serum with good recoveries. The limits of detection in bulk form and human serum were 6.7 x 10(-10) mol L(-1) and 8.1 x 10(-10) mol L(-1), respectively.

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.

Determination of indomethacin and mefenamic acid in plasma by high-performance liquid chromatography

Indomethacin and mefenamic acid are widely used clinically as non-steroidal anti-inflammatory agents. Both drugs have also been found effective to produce closure of patent ductus arteriosus in premature neonates. A simple, rapid, sensitive and reliable HPLC method is described for the determination of indomethacin and mefenamic acid in human plasma. As these drugs are not applied together, the compounds are alternately used as analyte and internal standard. Plasma was deproteinized with acetonitrile, the supernatant fraction was evaporated to dryness and the resulting residue was reconstituted in the mobile phase and injected into the HPLC system. The chromatographic separation was performed on a C18 column (250 x 4.6 mm I.D.) using 10 mM phosphoric acid-acetonitrile (40:60, v/v) as the mobile phase and both drugs were detected at 280 nm. The calibration graphs were linear with a correlation coefficient (r) of 0.999 or better from 0.1 to 10 micrograms/ml and the detection limits were 0.06 micrograms/ml for indomethacin and 0.08 micrograms/ml for mefenamic acid, for 50-microliters plasma samples. The method was not interfered with by other plasma components and has been found particularly useful for paediatric use. The within-day precision and accuracy of the method were evaluated for three concentrations in spiked plasma samples. The coefficients of variation were less than 5% and the accuracy was nearly 100% for both drugs.

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.

Gas chromatography/negative ion chemical ionization/tandem mass spectrometric quantification of indomethacin in plasma and synovial fluid

A procedure for the quantification of sub-nanogram per millilitre concentrations of indomethacin in plasma and synovial fluid has been developed using gas chromatography/negative ion chemical ionization/tandem mass spectrometry. The procedure is based on selected ion monitoring of the daughter ion at m/z 312 generated following decarboxylation of the 35Cl isotope peak of the indomethacin anion (m/z 356) formed from the pentafluorobenzyl ester of indomethacin in the ion source of the mass spectrometer. The internal standard, d2-indomethacin, has a daughter ion at m/z 316 formed from the corresponding 37Cl isotope peak. The limit of quantification was 0.1 ng ml-1 for both plasma and synovial fluid.

Rapid high-performance liquid chromatographic methods for the determination of overdose concentrations of some non-steroidal anti-inflammatory drugs in plasma or serum

Separate methods are described for the determination of the non-steroidal anti-inflammatory drugs diflunisal, indomethacin, fenoprofen, ibuprofen, ketoprofen, naproxen, mefenamic acid and piroxicam at overdose concentrations in human plasma or serum, using high-performance liquid chromatography and ultraviolet detection. A common extraction, involving protein precipitation with acetonitrile, is employed for all methods. A 25 cm Hypersil ODS (5 mu particle size) analytical column is used for all chromatographic separations, with a mobile phase of acetonitrile-acetate buffer (pH 4.2 or 4.8). The methods are all reproducible and can also determine concentrations that fall within the normal therapeutic range for each drug.

Fluorimetric determination of indomethacin in human serum by high-performance liquid chromatography coupled with post-column photochemical reaction with hydrogen peroxide

A high-performance liquid chromatographic method involving post-column photochemical reaction and fluorimetric detection has been developed for the determination of indomethacin in serum. The bioanalytical set-up consisted of single-pump system for post-column photochemical reaction. The mobile phase consisted of 0.07 M phosphate buffer (pH 6.6)-acetonitrile (65:35, v/v) containing 180 mM hydrogen peroxide. The column effluent was irradiated with UV light to give fluorescence. The fluorimetric detection was monitored with excitation at 358 nm and emission at 462 nm. The calibration curve was linear over the range 0.05-30 micrograms/ml by injecting a volume of 10 microliters of indomethacin solution. The detection limit (signal-to-noise ratio = 5) for indomethacin was 10 ng/ml using a 100-microliters aliquot of deproteinized serum. The mean recovery from serum was 94.3%.

A fully automated high-performance liquid chromatographic method for the determination of indomethacin in plasma

A fully automated method is described, which enables the determination of indomethacin in plasma by reversed-phase HPLC following on-line sample enrichment and clean-up on a short pre-column. The plasma sample is introduced directly into the column switching system. The pre-column, filled with a pellicular bonded phase, is first washed with phosphate buffer, pH 7.4. The compounds retained on the pre-column are then eluted in the fore-flush mode and separated on an octadecylsilica column with a methanolic phosphate buffer (pH 7.4) mobile phase. Indomethacin is determined spectrophotometrically at 254 or 260 nm. The effect of changes in the pH and flow rate of the washing eluent are studied. Under the conditions selected, memory effects can be avoided, the absolute recovery of the drug is 70% and the limit of detection 10 ng ml-1 for a 100 microliter injection of plasma. At a concentration of 100 ng ml-1, the relative standard deviations (RSD) are 1.7% (within-day) and 3.5% (between-day), respectively.

Administration of indomethacin for the prevention of periventricular-intraventricular hemorrhage in high-risk neonates

One hundred twenty-two preterm infants were enrolled in a placebo-controlled, double-blind trial using intravenous indomethacin for the prevention of periventricular-intraventricular hemorrhage (PVH-IVH). Before random assignment, data on the infants were stratified according to low-weight (500 to 999 g) or high-weight (1000 to 1500 g) subgroups. Cranial sonography was used to document the absence of PVH-IVH before enrollment and the occurrence of PVH-IVH during the 7-day protocol. Indomethacin, 0.1 mg/kg, or placebo was administered before 12 hours of age and at 24, 48, and 72 hours of age. Five patients receiving indomethacin and six receiving placebo were withdrawn before completion of the study. In the remaining 111 patients, the indomethacin and placebo groups were comparable with respect to gestational ages, maternal complications, Apgar scores, ventilatory requirements, complications of prematurity, and mortality rate. PVH-IVH developed in six of 56 infants who received indomethacin and 11 of 55 infants who received placebo (P = 0.174). Analysis of the individual strata showed that the indomethacin-treated infants in the low-weight subgroup sustained a higher mortality rate (11/17 vs 3/16; P = 0.008) without a reduction in the incidence of PVH-IVH. Infants in the indomethacin-treated high-weight subgroup demonstrated a significantly lower incidence of PVH-IVH (2/39 vs 8/39; P = 0.04), but the frequency of high-grade hemorrhages was comparable for both indomethacin- and placebo-treated groups. In summary, the prophylactic administration of intravenous indomethacin for the prevention of PVH-IVH cannot be recommended for infants less than 1000 g. In preterm infants between 1000 and 1500 g birth weight, indomethacin significantly reduced the incidence of PVH-IVH.