Biomedical subjects

D Whigan

Publications and source records attributed to D Whigan.

6 recordsLinked to original sources

PubMed2003

Quantitative determination of the HIV protease inhibitor atazanavir (BMS-232632) in human plasma by liquid chromatography-tandem mass spectrometry following automated solid-phase extraction.

A selective, accurate, and reproducible LC-MS-MS assay was developed for the determination of the HIV protease inhibitor atazanavir (BMS-232632) in human plasma samples. The method involved automated solid-phase extraction of atazanavir and a stable isotope analog internal standard (I.S.) using Oasis HLB 10 mg 96-well SPE plates. A portion of the reconstituted sample residue was injected onto a C(18) HDO analytical column which was configured with a triple quad mass spectrometer for analyte determination by positive ion electrospray. The assay was linear from 1.00 to 1,000 ng/ml with a lower limit of quantitation of 1.00 ng/ml. The inter- and intra-day coefficients of variation (C.V.) for the assay were <4%, and the accuracy was 99-102%. Atazanavir was stable in human plasma for at least 109 h at room temperature and for at least 1 year at -20 degrees C.

Atazanavir Sulfate↗

PubMed2001

Increased throughput in quantitative bioanalysis using parallel-column liquid chromatography with mass spectrometric detection.

The feasibility of quantitative bioanalysis by parallel-column liquid chromatography in conjunction with a conventional single-source electrospray mass spectrometer has been investigated using plasma samples containing a drug and its three metabolites. Within a single chromatographic run time, sample injections were made alternately onto each of two analytical columns in parallel at specified intervals, with a mass spectrometer data file opened at every injection. Thus, the mass spectrometer collected data from two sample injections into separate data files within a single chromatographic run time. Therefore, without sacrificing the chromatographic separation or the selected reaction monitoring (SRM) dwell time, the sample throughput was increased by a factor of two. Comparing the method validation results obtained using the two-column system with those obtained using the corresponding conventional single-column approach, the methods on the two systems were found to be equivalent in terms of accuracy and precision. The parallel-column system is simple and can be implemented using existing laboratory equipment with no additional capital outlays. A parallel-column system configured in this manner can be used not only for the within-a-run analysis of two samples containing two different sets of chemical entities, but also for the within-a-run analysis of two samples containing the same set of chemical entities.

Chromatography, Liquid↗

PubMed2000

Liquid chromatography/electrospray tandem mass spectrometry method for the quantitation of fosinoprilat in human serum using automated 96-well solid-phase extraction for sample preparation.

A sensitive, specific, accurate and reproducible liquid chromatography/electrospray tandem mass spectrometry method was developed and validated for the quantitation of fosinoprilat in 0.2 mL of human serum. The method employed acidification (with pH 4.0 sodium acetate buffer) of the serum samples to minimize the hydrolysis of the prodrug fosinopril to fosinoprilat prior to purification by automated 96-well solid-phase extraction. The required chromatographic separation of fosinoprilat and fosinopril was achieved isocratically on a Luna C8 analytical column (2 x 50 mm, 3 microm). The total run time was 2 min. The mobile phase contained methanol and water with 10 mM ammonium acetate. Detection was by positive ion electrospray tandem mass spectrometry. The standard curve, which ranged from 2.00 to 500 ng/mL, was fitted to a 1/x(2) weighted linear regression model. Fosinoprilat quality control (QC) samples used to determine the accuracy and precision of the method were prepared in human serum at concentrations of 5.00, 200, 400 and 1000 ng/mL. The assay accuracy was within 8% (dev). The intra- and inter-assay precisions were within 6 and 3% (RSD), respectively. Fosinopril QC samples used to gauge the rate of hydrolysis of fosinopril to fosinoprilat during the assay procedure were prepared in human serum at 500 ng/mL. The hydrolysis of fosinopril to fosinoprilat was </=1%. This degree of conversion would cause little error in the analysis of post-dose serum samples since such samples are known to contain low levels of the prodrug compared with the drug.

Analysis of Variance↗

PubMed1999

Sensitive triple-quadrupole mass spectrometric assay for the determination of BMS-181885, a 5-HT1 agonist, in human plasma following solid phase extraction.

A sensitive, selective, accurate, precise and reproducible triple-quadrupole liquid chromatographic-mass spectrometric assay was developed and validated for BMS-181885 (I), a 5HT1 agonist, in human plasma using BMS-181101 as the internal standard (IS). The method involved solid phase extraction of plasma containing I and the IS using Isoelute CN cartridges. The supernatant was then evaporated to dryness at 40 degrees C. The residue was dissolved in 100 microL of the injecting solvent. The HPLC column was ODS-3, 2 x 100 mm. The mobile phase comprised 10 mM ammonium formate (pH = 4) and acetonitrile, 55:45 v/v, used in an isocratic condition. The mass spectrometer was programmed to admit the protonated molecules at m/z 461 (I) and m/z 370 (IS) via the first quadrupole filter and to select reaction monitoring of ions at m/z 152 for I and IS for the quantification. Standard curves were fitted to a weighted quadratic function over the concentration range 0.2-200 ng/mL. The lowest standard concentration (0.2 ng/mL) was experimentally established as the lower limit of quantitation of the assay. The mean predicted quality control concentrations deviated within +/- 11% of the corresponding nominal values; the intra-assay and inter-assay precisions were within 7.0% relative standard deviation. I was stable in the injection solvent at 4 degrees C for at least 24 h and for at least three freeze-thaw cycles. Freezer stability of I in plasma was demonstrated for at least 3 months. The extraction recovery of I was established as 97%. The validated assay was applied to a pharmacokinetic study of I in humans.

Analysis of Variance↗

PubMed1993

Pharmacokinetics of pravastatin in elderly versus young men and women.

OBJECTIVE: To assess the effect of age on the pharmacokinetics of pravastatin in men and women. A secondary objective was to evaluate the effect of oral contraceptive steroids on the pharmacokinetics of pravastatin in young women. DESIGN: Open, single-dose study. SETTING: Clinical Pharmacology Unit of Princeton Medical Center for study in men and Hill Top Pharmatest, Cincinnati, for study in women. PARTICIPANTS: Normal, healthy male (aged 19-75 y) and female (aged 18-78 y) volunteers. INTERVENTIONS: Subjects received a single 20-mg dose of pravastatin after an overnight fast. MAIN OUTCOME MEASURES: The maximum plasma pravastatin concentration (Cmax), time required for that concentration to develop (Tmax), and the elimination half-life (beta t1/2). Serum concentrations of pravastatin and its major metabolite, the 3-alpha isomer, SQ 31,906, were determined at 12 intervals from 0.33 to 48 hours after the dose. Urine was collected cumulatively during the same period to determine urinary excretion of pravastatin and SQ 31,906. Both measures were used to determine pharmacokinetic parameters. RESULTS: The pharmacokinetic profiles of pravastatin and SQ 31,906 in young and elderly subjects of men and women differed little. Although the mean area under the concentration time curve of pravastatin was higher in the elderly and significantly higher in the elderly women, Cmax and beta t1/2 values were similar in the young and the elderly volunteers. Concomitant administration of oral contraceptives in young women did not affect the pharmacokinetics of pravastatin or SQ 31,906. CONCLUSIONS: The pharmacokinetics of pravastatin do not necessitate dosage adjustments in elderly men or women. No differences were detected between the disposition of the parent drug or its metabolite in men and women.

Adolescent↗

PubMed1990

Pharmacokinetics and pharmacodynamics of pravastatin alone and with cholestyramine in hypercholesterolemia.

The pharmacokinetics, pharmacodynamics, and safety of pravastatin, a new selective 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, were evaluated during monotherapy and with subsequent concomitant cholestyramine therapy in 33 patients with primary hypercholesterolemia in this randomized study. After 4 weeks, pravastatin monotherapy (5 mg, 10 mg, and 20 mg twice daily) significantly decreased total cholesterol by 17% to 24% (p less than 0.001 versus baseline) and low-density lipoprotein cholesterol by 23% to 35% (p less than 0.001). High-density lipoprotein cholesterol increased by 8% to 9%, and triglycerides decreased by 6% to 9%. The area under the serum concentration-time curve and maximum serum concentration of pravastatin showed dose-proportionality; time to maximum serum concentration and serum elimination half-life were independent of dose. When added to pravastatin therapy, cholestyramine enhanced the lipid-lowering effects of pravastatin. After 4 weeks of combination therapy, total cholesterol was reduced by 32% to 38% (p less than 0.001 versus baseline), and low-density lipoprotein cholesterol was reduced by 47% to 56% (p less than 0.001). High-density lipoprotein cholesterol increased by 11% to 18% (p less than 0.05). Pravastatin was well tolerated; no clinical adverse events directly attributable to the drug were reported.

Adult↗