High Performance Liquid Chromatographic Analysis of Tolmetin, Indomethacin and Sulindac in Plasma

Voltammetric analysis of dantrolene and its active metabolite with indomethacin in rat plasma

AIM

Differential pulse polarography was used for the concurrent analysis of the coadministered dantrolene (DAN) and indomethacin (IND) in plasma.

MATERIALS & METHODS

DAN and IND, Hanging mercury drop electrode and Britton-Robinson buffer at pH 5 were used. In plasma, cathodic reduction of DAN nitro group and its active metabolite at -0.2 V was done. IND was analyzed after carbonyl group reduction at -1.1 V.

RESULTS

Drugs determination in rat plasma with good recoveries and low limit of quantitation was done. Application to trace analysis of drugs in rat plasma was done with C_max and T_max determination.

CONCLUSION

This technique shows high sensitivity, simplicity and low cost. The method is US FDA validated and it is applicable to human level.

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.

High-performance liquid chromatographic analysis of indomethacin in serum

A rapid high-performance liquid chromatographic (HPLC) method for quantitative determination of indomethacin in serum is described. The assay was performed after single extraction of indomethacin and itraconazole (internal standard) from serum using diethyl ether and eluted from a 4 micron C-18 reversed-phase column at ambient temperature. The mobile phase consisted of ethanol:water:glacial acetic acid (65:34:1, v/v) pumped isocratically at a flow rate of 1.3 ml/min. The effluent was monitored at 254 nm. Quantification was achieved by the measurement of the peak area ratio, and the absolute recoveries ranged from 94 to 97%. Within-day coefficients of variation (CV) ranged from 2.72 to 5.70% and between-day CV varied from 3.61 to 6.1%. Stability testing indicated that indomethacin is stable for at least 30 days in serum at -20 degrees C. The method was used to study indomethacin pharmacokinetics in rabbits.

Differential pulse polarographic assay of tolmetin sodium capsules

Differential pulse polarography (DPP) is proposed as a direct method for the quantitation of tolmetin sodium in a capsule formulation (Tolectin--200 mg as the sodium dihydrate salt). Classical direct-current (DC) polarography has been employed to investigate the nature of the reduction occurring at the surface of the dropping mercury electrode (DME) using acetate buffer of pH 5.0 as the supporting electrolyte. The mean value of the results obtained by DPP expressed as a percentage of the stated amount, and the standard deviation, were found to be 99.87 +/- 0.43. The standard addition procedure used to assess the accuracy of the proposed method gave a mean percentage recovery of the total drug of 100.15 +/- 0.75%.

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.

Statistical optimization of a reversed-phase ion-pair liquid chromatographic method for the analysis of tolmetin sodium in dosage forms

A quantitative liquid chromatographic method in which tolmetin sodium is separated from an internal standard on a C18 column with detection at 317 nm has been developed with the aid of two statistical optimization procedures. The effects of simultaneously varying the pH, methanol-water ratio, and the concentrations of buffer and ion-pair reagent in the mobile phase were studied. A two-level factorial design was used to investigate the interactions among the variables, and the sequential simplex procedure was used to optimize the separation. A novel quality criterion was developed for the simplex optimization. Using synthetic mixtures, the mean recovery value +/- S.D. (n = 6) of tolmetin sodium was 98.7 +/- 0.19% for tablets and 98.5 +/- 0.12% for capsules. The assay results for commercial tablets and capsules were comparable to those obtained by the USP XXI procedure.

High-performance liquid chromatographic determination of tolmetin, tolmetin glucuronide and its isomeric conjugates in plasma and urine

A rapid and sensitive analytical procedure is described for the simultaneous measurement of tolmetin (T), tolmetin glucuronide (1 beta-TG) and the isomers of tolmetin glucuronide in plasma and urine. A reversed-phase liquid chromatographic system is used with an ion-pairing mobile phase of methanol-tetrabutylammonium hydrogensulfate buffered to pH 4.5 and kept at a constant temperature of 50 degrees C. Detection is by UV at 313 nm. Plasma (0.5 ml) and urine (0.1 ml) are collected in pre-cooled containers and immediately adjusted to pH 3.0 to minimize TG isomerization and hydrolysis. Samples are then deproteinated with acetonitrile, the supernatant is evaporated to dryness and reconstituted in an acetate buffer (pH 4.5), and 50 microliters are injected onto the system. Using zomepirac as the internal standard, the measurable, linear concentration ranges are 0.05-50 micrograms/ml for T in plasma and 0.025-50 micrograms/ml for T in urine. Chromatographic peaks representing T,1 beta-TG and three isomers of TG were identified, all with retention times less than 10 min. The need for special handling of biological samples is discussed.

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

A high-performance liquid chromatographic assay has been developed for the determination of a number of non-steroidal anti-inflammatory drugs in plasma. The samples were prepared by adding acetonitrile and perchloric acid to 200 microliter of plasma. Diclofenac, fenoprofen, ketoprofen, naproxen, phenylbutazone, piroxicam and sulindac were quantified in the supernatant produced using a mobile phase of phosphoric acid 0.03% (pH 2.5)-acetonitrile and a detecting wavelength of 254 nm. The reproducibility, linearity, precision and specificity of the assay were determined and found to be satisfactory. Alteration of the detection wavelength to 229 nm also permitted accurate determination of ibuprofen concentration in plasma. While reduction of the organic solvent content of the mobile phase and alteration of wavelength to 313 nm produced a system capable of quantifying salicylate and its metabolites in plasma and by further reducing the detecting wavelength to 237 nm, aspirin also was quantifiable. These methods have been applied in a cross-sectional study of medication compliance among rheumatoid arthritis patients treated with non-steroidal anti-inflammatory drugs.

Analysis of sulindac and metabolites in plasma and urine by high-performance liquid chromatography

A reversed-phase high-performance liquid chromatographic method with ultraviolet detection is described for the quantification of sulindac, sulindac sulfone and sulindac sulfide in plasma and sulindac, trans-sulindac, sulindac sulfone and sulindac sulfide in urine. Plasma samples are de-proteinized with acetonitrile and urine samples are injected directly following enzymatic hydrolysis of glucuronide metabolites. The resulting chromatograms are essentially free from endogenous interference and the limits of detection are 0.1 microgram/ml for plasma and 0.2 microgram/ml for urine for all of the above compounds.

The use of reversed phase cartridges (C18) in processing plasma for analysis of indomethacin by high performance liquid chromatography

The purpose of these studies was to develop a high performance liquid chromatographic (HPLC) assay for plasma levels of indomethacin. A reversed phase (C18 Sep-Pak) cartridge was used to process plasma for absorption of indomethacin, the internal standard, and impurities. The recovery of plasma indomethacin and the added internal standard was quantitative from 0.5 ml of plasma. The assay was linear from 50 micrograms/l to 10 mg/l without concentration of the effluent from the Sep-Pak cartridge. The intra-assay coefficients of variation, for ten injections each to calibrate points at 0.15, 0.30, 0.50 and 1.00 mg/l, were 8.15%, 6.29%, 5.47% and 5.39%, respectively and for duplicates of duplicate calibration points were 7.51%, 6.32%, 4.41%, and 2.05%, respectively. The inter-assay coefficients of variation were 8.49%, 6.48%, 5.10%, and 2.22%, respectively. The sensitivity of the assay can be increased by a 3-5 fold concentration of the effluent from the Sep-Pak and preliminary experiments have indicated that as little as 100 microliter of starting plasma can be utilized in the assay. The assay can be used to determine the concentration of indomethacin in small volumes of plasma. Since C18 Sep-Pak cartridges were employed to remove contaminating substances, sensitivity and reproducibility were both high while column longevity and efficiency were excellent.

Human pharmacokinetics of analgesics and methods for their determination in biological fluids

The main pharmacokinetic data of analgesics--biological half-lives, apparent volumes of distribution, total body clearances--obtained in humans, and their clinical relevance are summarized. Special emphasis has been given to the analytical methods used for the quantitative determination of these drugs in biological fluids.

Plasma indomethacin assay by reversed-phase ion pair high pressure liquid chromatography

A new rapid, selective and sensitive high pressure liquid chromatographic (HPLC) assay for indomethacin in plasma is described. The method involves precipitation of proteins with perchloric acid, followed by dichloromethane extraction using flurbiprofen as an internal standard. The organic solvent was evaporated and the residue dissolved in a water-methanol (2 + 3) phosphate buffer mixture with an apparent pH of 6.8. Aliquots of 100 microliters were injected automatically into the chromatograph. The separation of indomethacin was achieved on a reversed phase (C18, 10 micron) column with a mobile phase consisting of 65% (vol/vol) methanol in water solution of apparent pH 6.8 containing tetrabutylammonium hydrogensulfate as an ion pairing agent. Quantitation of indomethacin was performed by UV detection at 235 nm. At a 2.0 mg X l-1 concentration of indomethacin in plasma the analytical recovery was 82.9 +/- 3.4% (n = 7), the intra-day variability (CV) was 3.6% (n = 7) and the inter-day variability (CV) was 11.0% (n = 7). The calibration curve was linear (typical r-values greater than 0.990) in the range of plasma concentrations as usually found during indomethacin therapy (up to 6 mg X l-1). The limit of sensitivity is 0.025 mg X l-1. The metabolites O-desmethylindomethacin and O-desmethyldeschlorobenzoylindomethacin did not interfere with the method. The capacity of an analyst using this method with automated injection and peak integration is about forty samples in duplicate per day. The applicability of the method for pharmacokinetic studies is demonstrated.

Sensitive high-performance liquid chromatographic determination of indomethacin in human plasma. Pharmacokinetic studies after single oral dose

A sensitive high-performance liquid chromatographic assay for the specific determination of indomethacin at concentrations down to 20 ng/ml in human plasma is described. This method has been applied to investigate the disappearance of indomethacin from plasma of ten subjects following the intake of two formulations (Indocid and generic form). An initial half-life of 1.32 +/- 0.44 h-1 was found which is in good agreement with other findings, but the terminal phase was much longer (13.6 +/- 6.9 h-1) than previously reported. There is no difference between the two galenic forms (p less than 0.001).