Etodolac determination

This report presents various methods developed primarily at our laboratory for chromatographic resolution of racemates of several pharmaceuticals (e.g., -blockers, NSAIDS, anta-acids, DL-amino acids, Bupropion, Baclofen, Etodolac, Carnitine, Mexiletine). Recently, we developed methods for establishing molecular dissymmetry and determining absolute configuration of diastereomers (and thus the enantiomers) of (/< .S )-Baclofcn, (/d.SJ-Bctaxolol with complimentary application of TLC, HPLC, H NMR, LCMS this ensured the success of diastereomeric synthesis and the reliability of enantioseparation. 

The partition coefficient of etodolac was determined in the 1-octanol/water system, where the aqueous phase was buffered to pH 7.4. A logP value of 11.4 was obtained under these conditions. 

The 13C-NMR spectrum of etodolac has also been determined, and assignments for the observed resonance bands were determined using spindecoupling experiments. The assignments for observed resonance bands are provided in Table 5. 

A colorimetric method for the analysis of etodolac has been reported which is based on the formation of colored complexes with p-dimethyl-aminobenzaldehyde in the presence of sulfuric acid and ferric chloride [19]. Absorbance measurements were made at 591.5 nm, and the method was found to be linear over the concentration range of 10 to 80 pg/mL. This method was used to determine etodolac in bulk powder and other dosage forms. 

A simple, sensitive, and reproducible fluorimetric method for the determination of etodolac in bulk powder or dosage forms has been reported [19]. The method involves measurement of the native fluorescence at a wavelength of 345 nm, when ethanolic solutions of the drug were excited at 235 nm. The calibration was found to be linear over the concentration range of 96 to 640 ng/mL. 

A fluorimetric method developed for prodolic acid can also be used to quantitate etodolac in serum [20], This method involved using a 1 1 mixture of isoamyl alcohol and n-heptane to extract the drug from serum. An aliquot of the organic phase was then mixed with a 1 1 mixture of dimethyl sulfoxide and isoamyl alcohol, and the fluorescence of the clear solution was determined by excitation at 280 nm and scanning the emission spectra from 240-370 nm. The limit of detection of this method was about 2 pg/mL. 

A TLC method has been developed to determine etodolac and its metabolites (6-OH-etodolac and 7-OH-etodolac) in biological fluids and extracts (before and after enzyme hydrolysis) [15]. The method used silica gel plates and hexane-ethyl acetate-acetic acid (60 40 2, v/v) and hexane-ethyl acetate (70 30, v/v) solvent systems to separate the free carboxylic acid and methyl esters of etodolac and the two metabolites. The relative retention (Rf) values obtained under these conditions were 0.29,0.20 and 0.24 for etodolac, 6-OH-etodolac, and 7-OH-etodolac respectively. An Rf value of 0.45 was obtained for methyl ester of etodolac. 

A simple, accurate, and reproducible HPLC method has been developed to determine etodolac in presence of impurities (1-methyl and 8-methyl-etodolac) and in pharmaceutical formulations [14]. A Viospher ODS-2 (15 cm x 4.6 mm i.d., 5 pm particle size) HPLC column was used as stationary phase, and acetonitrile/0.05 M phosphate buffer (pH 4.75) (60 40 v/v) eluted at 0.8 mL/min was used as mobile phase. The system was thermostatted to 25 °C, and acetaminophen was used as an internal standard. Detection was achieved by measurement of the UV absorbance at 229 nm. The method was found to be linear over the concentration range of 2-20 pg/mL. The relative retention times for etodolac and acetaminophen were 2.2 and 2.9 min respectively. The retention times for the two impurities, 1-methyl-etodolac and 8-methyl-etodolac, were 1.4 and 3.8 min respectively. 

An HPLC method to determine etodolac during in vitro studies was developed [31]. Plasma was precipitated with acetonitrile, evaporated to dryness, and reconstitution in 25% acetonitrile. The HPLC consisted of a guard column, a 4 x 150 mm (5 pm particles) Cig column, and UV detection at 280 nm. The mobile phase was methanol / 0.01 M trifluoroacetic acid (25 75, v/v) at 1 mL/min. Etodolac was located at a retention time of 15.2 minutes. 

An HPLC method to determine racemic etodolac and its major metabolites in urine using a reverse-phase column has been developed [13]. Determination of etodolac in urine involved acidifying the diluted urine before extraction with cyclohexane-ethyl acetate (95 5, v/v). The organic layer was separated, evaporated, and reconstituted in solution of ibuprofen in acetonitrile (internal standard). The samples were injected onto a LiChrosper 100 RP-18 25 cm x 4 mm i.d., (5 pm particle size) column. 

A stereoselective GC method for determination of etodolac enantiomers in human plasma and urine was first reported as a preliminary method [35], and then as a validated method [36]. Sample preparation involved addition of (S)-(+)-naproxen (internal standard) and sodium hydroxide to diluted plasma or urine. The samples were washed with diethyl ether, acidified with hydrochloric acid, and extracted with toluene. ( )-(+)-naproxen was used as a derivatizing agent to form diastereomeric derivatives of etodolac. The gas chromatograph system used in this work was equipped with fused-silica capillary column (12 m x 0.2 mm i.d.) coated with high-performance cross-linked methylsilicone film (thickness 0.33 pm) and a nitrogen-phosphorous detector. The operating conditions were injector 250°C detector 300°C column 100-260°C (32 °C/min). 

Cosyns, L. Spain, M. Kraml, M. Sensitive high-performance liquid chromatographic method for the determination of etodolac in serum. J.Pharm.ScL, 1983, 72, 275-277... 

Koupai-Abyazani, M.R. Esaw, B. Laviolette, B. Etodolac in equine urine and serum determination by high-performance liquid chromatography with ultraviolet detection, confirmation and metabolite identification by atmospheric pressure ionization mass spectrometry. J. Anal. Toxicol. 1999, 23 (3), 200-209. 

Garcia, J. B., M. L. M. F. S. Saraiva, and J. L. F. C. Lima. 2006. Determination and antioxidant activity evaluation of etodolac, an anti-inflammatory drug, by sequential injection analysis. Anal. Chim. Acta 573 371-375. 

Spectrophotometric Determination of Etodolac in Pure Form and Pharmaceutical... 

Etodolac (ETD) is a non-steroidal anti-inflamatory antirheumatic drug. A survey of the literature reveals that there is no method available for the determination of ETD in pure form and pharmaceutical formulations by oxidation-reduction reactions. 

We describe three simple, sensitive and reproducible spectrophotometric assays (A-C) for the determination of etodolac in pure form and in pharmaceutical formulations. Methods A and B are based on the oxidation of... 

Our methods were successfully applied to the determination of etodolac in bulk and pharmaceutical formulations without any interference from common excipients. The relative standard deviations were < 0.76 %, with recoveries of99.87 % — 100.21 %. 

Etodolac (ETD), l,8-diethyl-l,3)4,9-tetrahydropyrano- [3,4-b]indole-1-acetic acid [1], is a non-steroidal anti-inflamatory antirheumatic drug (Scheme 1). A survey of the literature reveals that there are very few reported methods for the determination of ETD in biological fluids, pharmaceutical formulations and in presence of its enantiomer. Of those studies reported, the techniques used include chromatography, HPLC [2-5], GC [6-8], in addition to spectrofluorimetric [9] and spectrophotometric methods [9-11]. However, an extensive survey of the literature revealed that there is no method available for the simultaneous determination of ETD in pure form and pharmaceutical formulations by oxidation-reduction reactions. 

Ficarra R., Ficarra P., Calauro M. L., Costantino D. Quantitative high-performance liquid chromatographic determination of etodolac in pharmaceutical formulations. Farmaco 1991, 46 403—407. 

Giachetti C., Assandri A., Zanolo G., Brembilla E. Gas chromatography-mass spectrometry determination of etodolac in human plasma following single epi-cutaneous administration. Biomed Chromatoyr 1994, 8 180-183. 

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