RESUMO
An HPLC-MS/MS method was developed and validated for the determination of dihydralazine in human plasma. HPLC-MS/MS has not been used before in a published paper and provides better sensitivity and selectivity. Therefore a much easier sample preparation than published before is feasible (protein precipitation). As this substance is rather reactive and sensitive some specific care has to be taken hindering the conversion of the substance in whole blood and following human plasma after blood withdrawal. Hydrazines often are used for derivatization of aldehydes and ketones. With specific care (using 1,4-dithiothreitol (DTT) and cooling) dihydralazine can be preserved and analysed without decomposition or conversion in the tested range of 0.500-302 ng/mL of human plasma. The following inter-batch precision and accuracy of the Quality Control Samples resulted: QC-A (1.34 ng/mL plasma) with a precision of coefficient of variation (CV) 7.66% and an accuracy of 103.2%; QC-B (18.2 ng/mL 7.86%, acc. 101.3%); QC-C (258 ng/mL, 9.73%, acc. 98.3%). The inter-batch values of the LLOQ samples at 0.500 ng/mL were 7.17% for CV and accuracy of 106.4%. Mean recovery tested at the QC levels was found to be 103.8%. Specificity in six different plasma samples was good (<10% of the area of the LLOQ). Stability in plasma was tested under different conditions and was sufficient.
Assuntos
Anti-Hipertensivos/sangue , Cromatografia Líquida de Alta Pressão/métodos , Di-Hidralazina/sangue , Espectrometria de Massas em Tandem/métodos , Anti-Hipertensivos/química , Anti-Hipertensivos/farmacocinética , Disponibilidade Biológica , Cromatografia Líquida de Alta Pressão/normas , Estudos Cross-Over , Di-Hidralazina/química , Di-Hidralazina/farmacocinética , Ditiotreitol/química , Estabilidade de Medicamentos , Humanos , Modelos Lineares , Controle de Qualidade , Substâncias Redutoras/química , Valores de Referência , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Espectrometria de Massas em Tandem/normas , Temperatura , Fatores de TempoRESUMO
Comparative pharmacokinetic studies with high i.v. doses of dihydralazine (1, 5 and 7.5 mg/kg-1, respectively) were performed in rats, rabbits, and dogs. 1 was distributed in rabbits and dogs in two phases with half lives of 0.25-0.4 min and 1.0-2.0 min. The terminal slope was species dependent. The relative clearance values decreased in the order rabbit, rat, dog. High tissue concentrations were observed in rabbits and dogs in parenchymatous organs and endothelium (aorta). Skeletal and heart muscles belonged to the central compartment. The biliary excretion was low in rabbits. Dogs accumulated the drug in bile (bile/serum-ratios = 19-390). Maximally 5% of the given dose were excreted in rabbits with the 12-h-urine.
