ABSTRACT
The pharmacokinetic-pharmacodynamic (PK/PD) relationship of a novel platelet glycoprotein IIb/IIIa receptor antagonist, XU063, was evaluated as a function of biological matrix in beagle dogs. The disposition of 14C-radioactivity in various blood or plasma matrices and kinetics of inhibition of adenosine diphosphate (ADP) induced platelet aggregation were determined in beagle dogs following an intravenous infusion of 14C-XU063 at 2 micrograms/kg for 45 min. The 14C-radioactivity was maximum in platelet poor plasma (PPP) harvested from blood collected in EDTA and lowest in PPP harvested from blood collected in citrated vacutainers over the entire concentration versus time profile during and post infusion. The 14C-radioactivity values in blood and platelet rich plasma (PRP) were comparable and were between EDTA PPP and citrated PPP values. The resultant estimates of the PK and PD parameters of 14C-XU063 varied widely depending on the type of matrix used. The systemic clearance values for 14C-XU063 were 1 and 10 mL/min/kg for EDTA and citrated PPP, respectively. The values for the volume of distribution at steady-state were 0.2 and 1.3 L/kg, for EDTA and citrated PPP, respectively. The terminal elimination half-life appeared independent of the matrix with a median value of 2 h. The estimated ex vivo IC50 values of XU063 ranged from 0.4 ng/mL (citrated PPP, platelet free drug) to 7 ng/mL (EDTA PPP, total drug). These results demonstrated the dependence of PK and PD parameters of antiplatelet agent XU063 on the type of biological matrix used to determine concentrations of XU063. The pros and cons of various blood sample collection methods for the evaluation of PK/PD relationship of potential antiplatelet agents are presented.
Subject(s)
Isoxazoles/pharmacology , Isoxazoles/pharmacokinetics , Platelet Aggregation Inhibitors/pharmacology , Platelet Aggregation Inhibitors/pharmacokinetics , Platelet Glycoprotein GPIIb-IIIa Complex/antagonists & inhibitors , Adenosine Diphosphate/pharmacology , Animals , Blood Chemical Analysis/methods , Blood Proteins/metabolism , Blood Specimen Collection/methods , Dogs , Half-Life , In Vitro Techniques , Male , Metabolic Clearance Rate , Platelet Aggregation/drug effects , Protein BindingABSTRACT
A selective and sensitive high-performance liquid chromatographic assay for a novel cognitive enhancer, X9121 (I), and its mono N-oxide metabolite, XG696 (II), in dog plasma has been developed. Compounds I, II and internal standard (I.S.) were first extracted from dog plasma using a solid-phase Bond Elut Certify I 10-ml LRC reservoir extraction cartridge. Chromatographic separation of I, II and I.S. was conducted on a reversed-phase Zorbax Stable Bond cyano column. Ammonium acetate buffer (0.05 M, pH 6)-acetonitrile-triethylamine (75:25:0.1, v/v) was used as the mobile phase. Detection of all three compounds was by UV light absorbance at 313 nm. Using 0.5 ml of dog plasma for extraction, the minimum quantifiable limit was 10 ng/ml and the assay was linear from 10 to 5400 ng/ml. The coefficients of variation for intra-day precision ranged from 2.2 to 8.5% for I and from 2.5 to 9.8% for II. The coefficients of variation for the inter-day precision for these two compounds ranged from 2.6 to 9.0% and from 3.6 to 16.2%, respectively. The absolute percent differences for the accuracy results were within 11.0% of the spiked concentrations. Compounds I and II were stable in frozen plasma at -20 degrees C for at least 67 days.
Subject(s)
Chromatography, High Pressure Liquid/methods , Cyclic N-Oxides/blood , Pyridines/blood , Animals , Cognition/drug effects , Dogs , Female , Pyridines/metabolism , Pyridines/pharmacology , Reproducibility of Results , Spectrophotometry, UltravioletABSTRACT
A specific and sensitive HPLC assay for the determination of DMP 728 in dog and rat plasma has been developed. The method involves solid-phase extraction of DMP 728 and the internal standard from plasma using a C2 column. The extracted compounds are derivatized with benzoin under alkaline conditions. Using a mixture of acetonitrile and 0.1 M potassium phosphate buffer (25:75, v/v, pH 7.4) as mobile phase, the derivatized products are separated on a Regis semipermeable surface C8 column and monitored fluorometrically using 325 nm and 425 nm as excitation and emission wavelengths, respectively. The assay is linear from 2.5 to 1000 ng/ml in dog plasma and from 5 to 1000 ng/ml in rat plasma. The limit of quantitation is 2.5 ng/ml using 0.5 ml of dog plasma and 5 ng/ml using 0.5 ml of rat plasma. The assay has been used in pharmacokinetic studies of DMP 728 in dogs and rats.
Subject(s)
Chromatography, High Pressure Liquid/methods , Mesylates/blood , Peptides, Cyclic/blood , Platelet Aggregation Inhibitors/blood , Platelet Membrane Glycoproteins/antagonists & inhibitors , Acetonitriles , Animals , Benzoin , Chromatography, High Pressure Liquid/statistics & numerical data , Dogs , Female , Hydrogen-Ion Concentration , Hydroxides , Mesylates/pharmacokinetics , Peptides, Cyclic/pharmacokinetics , Phosphates , Platelet Aggregation Inhibitors/pharmacokinetics , Potassium Compounds , Rats , Reproducibility of Results , Sensitivity and Specificity , Temperature , Time FactorsABSTRACT
A sensitive and specific capillary gas chromatographic assay is reported for the quantitation of oxycodone in human plasma. The technique involves a single extraction of oxycodone and internal standard (hydrocodone) from plasma by toluene containing 1% isopropanol. Separation is achieved on a methyl silicone (HP-1) fused-silica capillary column (25 m x 0.2 mm I.D., 0.33 microns film thickness) and detection is by nitrogen-phosphorus selective mode. The minimum quantifiable limit is 1.8 ng/ml using 2 ml of plasma. The method is applicable to characterize the plasma profile of oxycodone in humans after a single oral 5-mg oxycodone hydrochloride tablet.