The detection of piroxicam, tenoxicam and their metabolites in equine urine by electrospray ionisation ion trap mass spectrometry

Abstract

An investigation has been conducted into the metabolism and urinary excretion of orally administered piroxicam and tenoxicam in the horse. The major component detected in urine after the administration of piroxicam was 5 0 -hydroxypiroxicam, which was detectable up to 24 h postadministration. Unchanged piroxicam was present only as a minor component. In contrast, unchanged tenoxicam was the major component observed after the administration of tenoxicam, being detectable for 72 h post-administration, while 5 0 -hydroxytenoxicam was a minor component. Piroxicam (4-hydroxy-2-methyl-N-2-pyridinyl-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide) and tenoxicam (4-hydroxy-2-methyl-N-2-pyridinyl-2H-thieno[2,3-e]-1,2-thiazine-3-carboxamide 1,1-dioxide) are structurally related cyclooxygenase (COX) inhibitor type anti-inflammatory drugs with potential for misuse in racing animals. Both compounds are known to be metabolised in humans primarily by hydroxylation of the pyridinyl substituent at the 5 0 -position (Fig. 1), 1,2 and in the case of tenoxicam this transformation has also been confirmed in the horse. 3 No study of the equine metabolism of piroxicam has yet been published.For the purposes of doping control, a thorough understanding of the metabolism of the drug concerned is obviously required. In addition, confirmatory analyses of small molecules must currently be performed by mass spectrometry, which in turn presupposes a knowledge of the relevant compound's mass spectral characteristics. This is a problem for piroxicam and tenoxicam, as to date the only mass spectral data for either of these compounds or their metabolites appearing in the literature are a positive ion atmospheric pressure chemical ionisation triple quadrupole LC/MS 2 product ion spectrum of tenoxicam 3 and a matrixassisted laser desorption/ionisation time-of-flight spectrum of piroxicam. 4 To remedy the situation, we now report the results of an investigation into the metabolism and urinary excretion of both piroxicam and tenoxicam following oral administration to the horse and provide a variety of ion trap mass spectral data for both compounds and their major urinary metabolites under electrospray ionisation (ESI) conditions. Human administrations were performed concurrently for the purpose of comparison.

Simultaneous determination of piroxicam, meloxicam and tenoxicam in human plasma by liquid chromatography with tandem mass spectrometry

“…At LLOQ level, CV values were ≤5.4% and RE values were −2.9 to 2.4% for piroxicam, meloxicam and tenoxicam (Table 2). This LLOQ value was smaller than that reported by de Jager et al [17] in 500 l of human plasma (0.72 ng/ml for piroxicam), by Wiesner et al [18] in 100 l of human plasma (8.96 ng/ml for meloxicam), and by McKinney et al [20] in 1 ml of equine urine (10 ng/ml for pirox- icam and tenoxicam). Therefore, the present method enables the pharmacokinetic studies of piroxicam, meloxicam or tenoxicam in after percutaneous application of piroxicam, meloxicam or tenoxicam.…”

“…Since the transdermal delivery avoids the gastrointestinal side effect and first-pass effect, many studies have been carried out in order to develop the percutaneous preparations of NSAIDs, including piroxicam and tenoxicam [1][2][3][4][5][6] number of high performance liquid chromatography (HPLC) methods with UV detection [7][8][9][10][11][12][13][14][15][16], amperometric detection [17] and tandem mass spectrometry (LC-MS/MS) [16,[18][19][20] were reported for the determination of piroxicam, meloxicam or tenoxicam in biological fluids; however, most of those methods presented insufficient sensitivity (limit of detection; 0.72-50 ng/ml), the use of large biological fluid volumes (0.25-1 ml plasma or urine) or chromatographic interferences. There was no LC-MS/MS method reported for the simultaneous determination of meloxicam, piroxicam and tenoxicam in biological samples.…”

Sonochemical oxidation of piroxicam drug: effect of key operating parameters and degradation pathways

“…On the other hand, TBP 9 and 10 show close retention times but no diagnostic fragments. However, the hydroxylation of PRX molecule in the pyridinyl ring and more specifically at the 5'‐position can be proposed for one of the isomeric TBPs since 5'‐hydroxypiroxicam is reported as a well‐known metabolite of PRX in the literature …”

“…However, the hydroxylation of PRX molecule in the pyridinyl ring and more specifically at the 5'-position can be proposed for one of the isomeric TBPs since 5'-hydroxypiroxicam is reported as a well-known metabolite of PRX in the literature. 28 In addition, two di-hydroxylated TBPs (TBP 6 and 11) are detected on the basis of +32 amu difference from the PRX molecule. TBP 11 shows a characteristic diagnostic fragment at m/z 210.0224 corresponding to the loss of C 6 H 4 N 2 O 3 suggesting that hydroxylation takes place on the pyridinyl ring.…”

Comparative study on two rapid and sensitive methods for quantitative determination of tenoxicam in tablets

“…Several analytical methods are described in recent literature such as mass spectrometric (McKinney et al, 2004), spectrofluorometric (Taha et al, 2002;Barary et al, 2004), potentiometric (El-Ries et al, 2003), polarographic (Atkopar and Tuncel, 1996), infrared spectrophotometric (Atay and Dincol, 1997) [7], coulometric (Nikolic et al, 1993), spectrophotometric (Amin, 2002;Garcia et al, 1999;El-Ries, 1998;Yener, Topaloglu, 1992;El Walily et al, 1997), derivative spectrophotometric (Taha et al, 2003) and high performance liquid chromatographic techniques (Hye et al, 2005;Sultan, et al, 2005;Taha et al, 2004;Bartsch et al, 2002;Abdel-Hamid, 2000;JosephCharles and Bertucat, 1999;Radhofer-Welte, Dittrich, 1998;Walily et al, 1997;Tracqui et al, 1995;Mason and Hobbs, 1995;Munera-Jaramillo, Botero-Garces, 1993;Carlucci et al, 1992;Dixon et al, 1984).…”