Validation of a chromatographic method to determine E-6006 and its metabolite E-6332 in rat and dog plasma by solid-phase extraction and capillary gas chromatography. Application in pharmacokinetics

E-6006, 5{alpha [2-(dimethylamino)ethoxy]-2-thienylmethyl}-1-methyl-1H-pyra zole is a new antidepresive compound and E-6332, 5-{alpha-[2-(methylamino)e thoxy]-2-thienylmethy}-1-methyl-1H-yrazole is its desmethylate metabolite. With the aim of quantifying E-6006 and E-6332, simultaneously in rat or dog plasma, a method of analysis based on solid-phase extraction coupled with capillary gas chromatographic system with N-P detection was developed and v alidated. E-6006, E-6332 and its internal standard (E-4018) were isolated f rom plasma using an off-line semiautomatic solid-phase extraction method. G as chromatography separations were carried out by means of 12 m length, 0 2 mm (i.d.) and 0.33 mum (f.t.) ULTRA 1 type capillary column in splitless m ode of injection at 190 degreesC, with a TSD or specific nitrogen-phosphoru s detector. No peaks interfering with the quantification of E-6332 and E-60 06 were observed. The limit of quantification was 5 ng/ml with a precision and accuracy < 17%. The peak height ratios were proportional to E-6332 and E-6006 concentration over the range from 5 to 600 ng/ml (r(2) > 0.998). Mea n recoveries of E-6332, E-6006 and internal standard from rat plasma were b etween 57.1 and 82.6. Intra-assay precision coefficients were < 8.0 and < 1 1.8%, respectively, for E-6332 and E-6006, with an accuracy < 12.6 and < 9. 7%. Both inter-assay precision and accuracy were within acceptable limits ( < 15%). In dog, the results were very similar to those obtained in rat. To show an example of the suitability of the method to determine E-6332 and E- 6006, plasma profiles obtained after. single oral and intravenous administr ation of 20 mg/kg to rats and 25 mg/kg to dogs are reported. (C) 2001 Elsev ier Science B.V. All rights reserved.