Toxicokinetics of ergovaline in the horse after an intravenous administration.

The toxicokinetics of ergovaline (an ergopeptine mycotoxin present in some grasses infected with endophytic fungus of the genus Neotyphodium) were studied after intravenous administration of a single dose of 15 microg/kg bwt in four gelding horses. Plasma ergovaline concentrations were measured by high performance liquid chromatography, and the kinetic data were described by a three-compartment model. The elimination half-life and the total clearance of ergovaline were found to be 56.83 +/- 13.48 min and 0.020 +/- 0.004 L/min x kg, respectively. According to the toxicological data previously reported in the horse, and in spite of the very low dose administered, clinical signs were observed, including excessive coolness of the ears and the nose, excessive sweating and prostration.

Analysis of ergovaline in milk using high-performance liquid chromatography with fluorimetric detection.

A high-performance liquid chromatographic method for the determination of the mycotoxin ergovaline in goat's milk is described here. Ergotamine was used as an internal standard. For a sample size of 5.0 ml, the cleanup method included precipitation of milk protein with acetone. Then, ergovaline was extracted twice with chloroform and purified by elution on an Ergosil column. HPLC separation of the extract was accomplished on a C18 column: an isocratic elution, using acetonitrile-ammonium carbonate, was performed, and the analyte was detected by fluorimetry. The method was found to be linear between 0.7 and 8 ng ml(-1), a mean recovery rate of 99.8% was obtained, and the described assay appeared both repeatable and reproducible. The limit of detection and the limit of quantitation of ergovaline in milk were 0.2 ng ml(-1) and 0.7 ng ml(-1), respectively. In order to apply the proposed method, four lactating goats were administered the toxin intravenously at a dose of 32 mg kg(-1) body weight. The concentrations of the drug in plasma and milk were then determined at standardized intervals. Ergovaline (unequivocally identified by LC-MS-MS) could not be detected in the milk beyond eight hours post-dosing. Therefore, in goats, milk does not appear to be a major excretion route for the unmetabolized toxin.

Rapid analysis of ergovaline in ovine plasma using high-performance liquid chromatography with fluorimetric detection.

A rapid high-performance liquid chromatographic method for the determination of the mycotoxin ergovaline in ovine plasma is described here. Ergotamine was used as an internal standard. A simple extraction procedure with diethyloxide was carried out, before chromatography on a C8 column, with the excitation and emission wavelengths fixed at 250 and 420 nm respectively, on a fluorimetric detector. The method, which was found to be linear between 3.5 and 15 ng/ml, had good specificity, precision and accuracy. The limit of quantification and the limit of detection were 3.5 and 1.2 ng/ml, respectively. A preliminary application of the described assay to a plasma kinetic study, after intravenous administration of a single dose of ergovaline (17 micrograms/kg body mass) to four sheep, showed a very rapid decrease of the plasma ergovaline levels. The terminal half-life and the total clearance of the mycotoxin were found to be 23.6 min and 0.020 l/min kg-1 body mass, respectively.

Pharmacokinetics and haematological parameters of recombinant human erythropoietin after subcutaneous administrations in horses.

The pharmacokinetics of recombinant human Epo (rHuEpo) were investigated after subcutaneous administration to horses. Four horses received a single 30IU kg-1 dose of rHuEpo. One horse received three repeated doses of 120 IU kg-1 at 48 h intervals. Plasma erythropoietin (Epo) was measured by radioimmunoassay. In both cases pharmacokinetic parameters were evaluated using a one-compartment open model and first-order input and output rates. The mean values (+/-SD) for elimination half-life, CL/F, and Vd/F after a single dose were 12.9 +/- 3.34 h, 11.8 +/- 4.96 L h-1, and 233 +/- 126 L, respectively. After repeated doses, elimination half-life, CL/F, and Vdss/F were 11.3 h, 8.94 L h-1, and 145.6 L, respectively. No significant differences were observed between the haematological parameters after a single 30 IU kg-1 administration compared to baseline values. Multiple and high doses of rHuEpo modified red blood cells, haemoglobin, and hematocrit. According to our results, plasma Epo assay can help, during an antidoping control procedure, to support a positive result only up to 72 h after the last rHuEpo.

Chiral inversion of fenoprofen in horses and dogs: an in vivo-in vitro study.

Fenoprofen (FPF) is a chiral non-steroid antiinflammatory drug, marketed as a racemic mixture of its R(-) and S(+) enantiomers. Its stereoselective disposition in humans and animals is due to a chiral inversion converting R(-)FPF into S(+)FPF. The first step of this reaction, which produces an acyl-CoA thioester, is catalysed by an acyl-CoA ligase. A stereospecific high performance liquid chromatography assay was used to study the disposition of FPF enantiomers in four geldings and three male beagle dogs, following intravenous doses of racemic FPF (1 mg/kg in horses), R(-)FPF (0.5 mg/kg in horses, 1 mg/kg in dogs), and S(+)FPF (0.5 mg/kg in horses, 1 mg/kg in dogs). A unidirectional stereoinversion of the R(-) enantiomer into its optical antipode (38% in horses, 90% in dogs) was demonstrated. This explained the clear enantioselective behaviour of FPF in both species. Acyl-CoA ligase activity (Km = 473.2 +/- 92.5 microM; Vmax = 23 +/- 3.3 nmol/min/mg) has also been quantified in vitro on equine hepatic microsomes, using a high performance liquid chromatography method to measure thioester formation. The present study showed that, in horses and dogs, as previously demonstrated in rats and sheep, the R(-)FPF clearance was better correlated with ligase activity than with inversion rate. A highly significant linear relationship was demonstrated between these variables.

Enantioselective glucuronidation and subsequent biliary excretion of carprofen in horses.

Carprofen (CPF) enantiomers and their glucuronide conjugates (GLUC) were measured in plasma and bile of horses after IV administration of the racemic compound (0.7 mg/kg of body weight). The CPF was detectable in plasma for up to 72 hours after dosing, whereas GLUC appeared early (time for maximal plasma concentration, 1 hour) and was measurable transiently at low concentration (maximal plasma concentration, 0.5 microgram/ml). The enantiospecific plasma profiles indicated a clear predominance of R-CPF, whereas the stereoselectivity of the glucuronides favored S-GLUC. At 1, 2, and 12 hours after administration of the drug, bile concentrations of GLUC were high compared with those in plasma and enantioselectivity favored S-GLUC. These data indicate that the higher body clearance observed for S-CPF is a consequence of the enantioselectivity in liver glucuronidation and subsequent biliary excretion of the S enantiomer of the drug.

Kinetics and haematological effects of erythropoietin in horses.

A plasma kinetic study of erythropoietin (EPO) was carried out in 4 horses after subcutaneous administration (30 IU/kg bwt) of recombinant human erythropoietin (rhEPO). At standardized intervals for 48 h before injection and for 60 h post-administration, the EPO plasma levels were determined with an immunoradiometric assay based on a sandwich technique. The peak plasma concentration (30-113 mIU/ml) was observed after a delay ranging from 6 to 9 h post-administration and the drug levels reached a physiological value around 60 h following rhEPO injection. Moreover, reference values for plasma EPO concentrations, which were separately determined in 70 racehorses and 34 sport equines, ranged between 0 and 9 mlU/ml. After drug administration, no significant variations in red blood cell count, haemoglobin concentration, haematocrit or mean red blood cell volume were observed in the 4 animals. Further, minimal variations in these parameters were detected in a horse which received three 120 IU rhEPO/kg bwt doses successively. Therefore, high rhEPO doses are probably required to induce a visible haematological effect in equine species.

Identification of a benzhydrolic metabolite of ketoprofen in horses by gas chromatography-mass spectrometry and high-performance liquid chromatography.

A benzhydrolic metabolite of ketoprofen, formed by reduction of the keto group of the drug, has been identified by gas chromatography-mass spectrometry in equine plasma and urine. After partial synthesis, its structure has been confirmed by UV, IR and 1H NMR spectroscopy. The kinetics of ketoprofen and this metabolite have been monitored in plasma by high-performance liquid chromatography. The two products were quantified in plasma up to 4 and 3 h, respectively, and were detected in urine up to 72 and 24 h, respectively, after a single intravenous administration to horses at the dose of 2.2 mg/kg. Simultaneous detection of both compounds increases the reliability of antidoping control analysis.

Pharmacokinetics of tolfenamic acid in the horse.

The pharmacokinetics of tolfenamic acid were studied in five ponies after an intravenous (iv) administration (2 mg/kg bodyweight [bwt]) and in four horses after an oral administration (30 mg/kg bwt) of tolfenamic acid. The plasma levels were determined by high pressure liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). For the iv administration, a three-compartment model was used to represent the plasma concentration-time curve of the drug. The elimination half-life of the compound was 6.1 +/- 1.5 h, the total body clearance was 72.4 +/- 16.7 ml/kg bwt/h and the steady-state volume of distribution 0.32 +/- 0.11 litres/kg bwt. For the oral administration, absorbtion was delayed with a mean lag-time to absorption of 32 +/- 28 mins. The peak plasma concentration 11.1 +/- 0.69 micrograms/ml was observed after a highly variable delay ranging from 1.9 to 6.5 h post administration. The terminal half-life (4.2 +/- 0.48 h) was very similar to that obtained after iv administration. Tolfenamic acid could not be detected in equine plasma with the described analytical methods more than 48 h after drug administration.

Identification of a tolfenamic acid metabolite in the horse by gas chromatography-mass spectrometry.

A tolfenamic acid metabolite, a hydroxylated product, has been identified in equine plasma and urine samples using gas chromatography-mass spectrometry in the electron-impact and chemical-ionization modes. The method also allows the qualitative monitoring of the elimination of the drug and its metabolites from plasma. The two compounds are detected up to 48 and 24 h, respectively, after a single oral administration of a 30 mg/kg dose. The simultaneous detection of the two products increases the reliability of anti-doping control analysis.

Metabolism of metapramine in vitro by chemical model systems and rat liver microsomes.

Metapramine (Timaxel) was oxidised by hepatic microsomes from rat and by biomimetic chemical systems; vanadyl acetylacetonate-iodylbenzene, phthalocyanin-iron II-iodosylbenzene, meso tetraphenyl porphyrine-iron III chloride-iodosylbenzene and Fenton's reagent. The major metabolite in all cases was the monodemethylated product formed by oxydative removal of the methyl group on the endocyclic nitrogen atom.

Identification of a flunixin metabolite in the horse by gas chromatography-mass spectrometry.

The main metabolite of flunixin, a hydroxylated product, has been identified by gas chromatography-mass spectrometry and 1H NMR spectroscopy in equine urine and plasma. The method also permits the qualitative monitoring of the urinary elimination of the drug and its metabolite. The two products are detected up to 175 and 54 h, respectively, after a single intravenous administration at the dose of 1 mg/kg. Simultaneous detection of the two compounds increases the reliability of anti-doping control analysis.

[Flunixin and its use in horses]. / La flunixine et son utilisation chez le cheval.

Flunixin is a non-steroidal anti-inflammatory agent, with a potent analgesic activity and a slight toxicity. It is largely used in horses, in the form of meglumine salt, for the treatment of inflammatory diseases or colics, and often identified in dopage cases. Physical and chemical properties of the drug, its pharmacological and toxicological properties, and its use in equine species are depicted.

[Chronopharmacokinetics of phenylbutazone in the horse. Application to antidoping control]. / Chronopharmacocinétique de la phénylbutazone chez de cheval. Application au contrôle antidopage.

Chronopharmacokinetics of intravenous phenylbutazone in the horse was studied with the aim of antidoping control. Among parameters studied, the single one which seemed to depend on circadian rhythm was the elapsed time between the injection and the plasmatic peak. There was no relationship between the injection time and the both parameters: half-life and time required to reach the forensic level of 4 micrograms/ml. This later, and oxyphenbutazone/phenylbutazone ratio, should depend on individual factors. Therefore, the injection time should not be a main parameter for the phenylbutazone evaluation in the case of antidoping control.

High index gradient in glass by ion exchange.

A gradient index having 0.22 as maximum value has been obtained in a TiF(6) Schott glass by the ion exchange technique. Index profiles and ionic concentration are presented. The reasons for such a high gradient are analyzed.

Realization of Schmidt plates by ion exchange in glass.

A new technique is presented to realize Schmidt plates by ionic exchange controlled by electric field into adjacent areas. The shape and optical path in these areas may be adjusted very accurately. A preliminary plate has been made with three areas, and results are analyzed.

Graded-index surface or buried waveguides by ion exchange in glass.

Graded-index surface or buried waveguides have been realized by thermal or electrically induced ionic exchange in glass. Deep waveguides can be obtained up to 200 microm when Li(+) ions are used. Using Ag(+) ions, buried waveguides can be obtained with a maximum index at 80 microm into the substrate. Typical losses for these devices are 0.5 dB/cm. Maximum index variations can be tuned from 0 to 0.11.