| Studying on preclinical pharmacokinetics is an important part of evaluation on novel drugs. Establishing a sensitive and specific quantitative analysis method is the prerequisite of the study, dealing with mathematics method to describe the changing regularity in drug and other exogenous material quantitatively, to interpret the change after taking drug in body, such as absorption, distribution, metabolism, excretion and the significance in pharmacology and toxicology. Milbemycin oxime belongs to macrolide antibiotic, was a mixture of milbemycin A3 and A4 oxime derivate, mainly used as exterior and interior anthelminthic of dogs and cats, and is effective to prevent and control dirofilaria immitis infection, and also does well in expelling toxocara canis, ancylostome, whipworm and sarcoptes scabiei, bdella cardinalis and so on. People focus on it as its character of high effective and low toxic, following with the protective expiration date of this drug abroad, it will be used in China in the near future. For the convenient of clinical application, are the main content and results it is necessary to study the Pharmacokinetics, and that's also the reason we do the study here.Here a sensitive LC-MS/MS method was developed to detect milbemycin oxime in dog plasma, solid phase was used in the pre-processing, and it had been used to investigate pharmacokinetics of milbemycin oxime in dogs receiving a single oral dose of 0.125, 0.25, 0.5mg·kg-1. Chromatography was performed using hypersil C18 column (150mm×4.6mm I.D., 5μm) as stationary phase and acetonitrile-5mmol·L-1 ammonium acetate (85:15, v/v) as mobile phase in the isocratic mode at a flow rate of 0.25mL·min-1. An ESI source was used as detector in the selected-ion-monitoring mode.In the scope from 5 to 500ng·mL-1, concentration and response ratio of Eilbemycin oxime show satisfactory linear correlation, sample work curve in dog blood plasma is y=94.2379x-60.4477,r=0.999551, detectability and limit of quantitation is 2.5ng·mL-1 and 5 ng·mL-1. The main pharmacokinetic parameters were fitted with one-compartment model, such as sample coefficient of recovery, groundmass inhibition ratio, method specificity, precision, stability. After milbemycin oxime was administered to beagle dogs at an oral single dose of 0.125, 0.25 and 0.5mg·kg-1 respectively, intravenous injection dose of 0.25 mg·kg-1, compared with the import milbemycin oxime. Blood collected after administration at different time was detected by LC-MS/MS, pharmacokinetic parameters were analyzed with 3p97 pharmacokinetics software.The results showed that the dynamics processes of three dose groups in dogs vivo were fitted with single compartment models, parameters including Cmax, Tmax, t1/2, AUC0-t, AUC0-∞were 36.5, 76.11, 182.05ng·mL-1; 4.14, 4.27, 4.06h; 15.06, 11.09, 9.76h; 964.34, 1568.61, 3440.47ng·h mL-1;985.83, 1663.12, 3558.04ng·h mL-1. The pharmacokinetic parameters of the control drug were 4.25ng·mL-1, 4.07h,11.66h, 1517.99 ng·h mL-1, 1649.64 ng·h mL-1. After administration of 48h, following with absorbing in blood, more than 90% of the drug was distributed to tissues and humour, then fall down, elimination half life was a little longer. The absolute bioavailability of milbemycin oxime was estimated to be 76.57%.The main pharmacokinetics parameters of milbemycin oxime and the control drug were detected with single-bilateral T test, the result showed there was no significant difference between preparation, every t1 and t2 was larger than 2.132, the 90% confidence intervals was between 80% and 120%, was in accord with the request of bioequiavailability. |
