Pharmacokinetics of tramadol administered by intravenous and intramuscular routes to female dogs submitted to ovariohysterectomy

The objective of the present study was to implant a method using a sensitive and specific system, and validate the whole analytical method to obtain an efficient tool for analyses of tramadol in plasma dogs, and to evaluate the pharmacokinetics of tramadol following intravenous (i.v.) and intramuscular (i.m.) administration of this drug in females dogs submitted to castration. The pharmacokinetics of tramadol were examined following i.v. or i.m. tramadol administration to five female dogs in each group submitted to ovariohysterectomy (dosage=2 mg/kg). In relation to intravenous administration, the half-time for the distribution process (t1/2d = 0.18 ± 0.12 h); the total body clearance was 0.60 ± 0.50 L/h/kg, half-life of elimination (t1/2²) was 1.24 ± 0.69 h. Statistically differences between parameters obtained after i.v. and i.m. was significant only to AUC0[i: 3362.07 ± 1008 and 1604.55 ± 960.02 (ng.h/mL), respectively. The F was 48.00 ± 43.30%. The assay for tramadol described has been demonstrated to meet all requirements for clinical PK studies. In particular, the method has satisfactory specificity, linearity, accuracy and precision range over the concentration examined. O objetivo do presente estudo foi de implantar um método sensível e específico, e validar toda a metodologia para obter uma ferramenta eficiente para a análise do tramadol em plasma de cadelas, e avaliar a farmacocinética do tramadol após a administração do mesmo pelas vias i.v. e i.m. em cadelas submetidas à castração. A farmacocinética do tramadol foi examinada após a administração do tramadol por ambas as vias, em cinco cadelas em cada grupo submetidas à ovário histerectomia (dose = 2 mg/kg). Em relação à administração intravenosa, a meia-vida de eliminação (t1/2β) foi de 1,24 ± 0,69 h. Encontrou-se diferenças significantes somente nos parâmetros AUC0→∞: 3362,07 ± 1008 and 1604,55 ± 960.02 (ng.h/mL), pelas vias i.v. e i.m. respectivamente. O F foi de 48,00 ± 43,30%. O estudo descrito neste artigo demonstrou atingir todas as exigências para os estudos clínicos em farmacocinética. Especificamente, o método apresentou especificidade, linearidade, exatidão e precisão satisfatórias no intervalo de concentrações examinadas.