Gilbert N. Lam

A high-performance liquid chromatography-tandem mass spectrometric method for the determination of pharmacokinetics of ganaxolone in rat, monkey, dog and human plasma.

A method for determining concentration levels of ganaxolone in rat, monkey, dog and human plasma was validated in the range of 5-1500 ng/ml using a 200-microl plasma sample volume. This validation report describes the linearity, specificity. sensitivity, reproducibility, accuracy, recovery and stability of the analytical method. The inter-day C.V. ranged from 0.5 to 9.2%, intra-day C.V. from 0.7 to 8.8% and intra-day accuracy (mean absolute percentage difference) ranged from 0.0 to 14.0% for rat, monkey, dog and human plasma. The method was used for the routine analysis of ganaxolone in rat, monkey, dog and human plasma and summary of the pharmacokinetic data are presented.

Nanogram level quantitation of oxycodone in human plasma by capillary gas chromatography using nitrogen—phosphorus selective detection

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.

Biological matrix-dependent pharmacokinetic and pharmacodynamic parameters of a novel platelet glycoprotein IIB/IIIA receptor antagonist, XU063, in beagle dogs

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.

Development of a high-performance liquid chromatographic-tandem mass spectrometric method for the determination of pharmacokinetics of Co 102862 in mouse, rat, monkey and dog plasma.

A method for determining concentration levels of Co 102862 in mouse, rat, monkey and dog plasma was validated in the range of 5 to 2000 ng/ml using 200 microl plasma sample volume. This validation report describes the linearity, specificity, sensitivity, reproducibility, accuracy, recovery and stability of the analytical method. The inter-day RSD ranged from 3.5 to 10.1%, intra-day RSD from 0.6 to 5.7% and intra-day accuracy (mean absolute percent difference) ranged from 2.2 to 14.9% for rat, monkey and dog plasma. A mini-validation (5-2000 ng/ml) of Co 102862 was performed in mouse plasma using the same methods. Additionally, the assay range at the low end was successfully extended to 0.5 ng/ml for monkey plasma. The method was used for the routine analysis of Co 102862 in mouse, rat, monkey and dog plasma and summary of the pharmacokinetic data are presented.

Determination of a novel cognitive enhancer, X9121, and its mono N-oxide metabolite, XG696, in dog plasma by reversed-phase high-performance liquid chromatography with ultraviolet detection

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.

Determination of brequinar in rat plasma by direct deproteinization and reversed-phase high-performance liquid chromatography with ultraviolet absorbance detection

A direct deproteinization method for the determination of brequinar in rat plasma by high-performance liquid chromatography (HPLC) has been developed. This assay avoids the use of dichloromethane, a known carcinogen, in an existing extraction method. Acetonitrile was used to denature plasma proteins and the supernatant was injected onto the HPLC column. Chromatographic separation of brequinar was conducted on a Biophase octyl column using a mixture of acetonitrile and 0.1 M phosphoric acid (50:50, v/v) as the mobile phase and detection of brequinar was by UV absorbance at 254 nm. The method has been validated in rat plasma over the concentration range of 0.05-50.00 micrograms/ml which is adequate for the determination of pharmacokinetics of brequinar in animals.

Determination of a novel sigma receptor antagonist, DuP 734, in rat plasma by reversed-phase high-performance liquid chromatography with ultraviolet detection

A selective high-performance liquid chromatographic (HPLC) assay for a sigma receptor antagonist, DuP 734 (I), in rat plasma has been developed. Compound I and internal standard, XC031 (I.S.), were first extracted from plasma into an ethyl acetate-toluene mixture (3:7, v/v) and then back-extracted into freshly prepared phosphoric acid (0.03 M). Separation of I and I.S. with no interference from endogenous substances was achieved on a reversed-phase octyl column and detection was by UV at 229 nm. The mobile phase consisted of acetonitrile-glacial acetic acid-triethylamine-0.05 M ammonium acetate (670:4:2:2000, v/v). Using 0.5 ml of rat plasma for extraction, the limit of quantitation was 43 ng/ml and the assay was linear from 43 to 8536 ng/ml. The intra- and inter-day coefficients of variation ranged from 0.7 to 3.0%, and from 1.4 to 14.5%, respectively, over the entire concentration range. The accuracy was within 16.1% of the spiked concentrations. I was stable in frozen plasma at -20 degrees C for at least 68 days.