Simultaneous LC-MS/MS quantitation of acetaminophen and its glucuronide and sulfate metabolites in human dried blood spot samples collected by subjects in a pilot clinical study.

Background: In support of a pilot clinical trial using acetaminophen as the model compound to assess dried blood spot (DBS) sampling as the method for clinical pharmacokinetic sample collection, a novel sensitive LC-MS/MS method was developed and validated for the simultaneous determination of acetaminophen and its major metabolites, acetaminophen glucuronide and sulfate, in human DBS samples collected by subjects via fingerprick.

Results: The validated assay dynamic range was from 50.0 to 5000 ng/ml for each compound using a 1/8´´ (3-mm) disc punched from a DBS sample.

Pharmacokinetics of single and multiple oral doses of valsartan/amlodipine (80/5 mg) in healthy Chinese subjects.

Objective: The efficacy and safety of valsartan/amlodipine combination have been demonstrated for the treatment of hypertension. In China, where the prevalence of hypertension is increasing the pharmacokinetic study of valsartan, amlodipine assumes significance. The aim of this study was to characterize the pharmacokinetics (PK) of valsartan and amlodipine following single- and multiple-dose oral administrations of valsartan/ amlodipine 80/5 mg fixed-dose combination in healthy Chinese subjects.

An automation-assisted generic approach for biological sample preparation and LC-MS/MS method validation.

Background: Although it is well known that automation can provide significant improvement in the efficiency of biological sample preparation in quantitative LC-MS/MS analysis, it has not been widely implemented in bioanalytical laboratories throughout the industry. This can be attributed to the lack of a sound strategy and practical procedures in working with robotic liquid-handling systems.

Results: Several comprehensive automation assisted procedures for biological sample preparation and method validation were developed and qualified using two types of Hamilton Microlab liquid-handling robots.

Quantitative analysis of NIM811, a cyclophilin inhibitor, in human dried blood spots using liquid chromatography-tandem mass spectrometry.

A high-performance liquid chromatography-tandem mass spectrometric (LC-MS/MS) method has been developed and validated for the quantitative analysis of NIM811, a cyclophilin inhibitor, in human dried blood spot (DBS) samples, which were produced by spotting 20 μl whole blood onto FTA cards. A 3mm disc was cut from the DBS samples and extracted using methanol, followed by liquid-liquid extraction with MTBE. The reconstituted extracts were chromatographed using a Halo C(18) column and gradient elution for MS/MS detection.

Developing a robust ultrafiltration-LC-MS/MS method for quantitative analysis of unbound vadimezan (ASA404) in human plasma.

Ultrafiltration of human plasma in combination with LC-MS/MS has been increasingly used in the quantitative analysis of the free fraction of drug candidates for PK/efficacy assessment. In addition to controlling the pre-incubation and centrifugation temperatures, some important factors that must be investigated and addressed include: (1) possible nonspecific binding, (2) possible impact of freeze/thaw cycles of plasma samples and extended storage of plasma samples at room temperature on the analyte recovery prior to ultrafiltration, and (3) identification of the appropriate assay dynamic range to avoid unnecessary dilutions. These factors were explored in the development and validation of a robust LC-MS/MS assay for the quantitative analysis of unbound vadimezan (ASA404) in human plasma.

An investigation of incurred human urine sample reanalysis failure.

Background: In this case study, urine samples were collected and transferred before the presence of a small degree of nonspecific binding was identified for the analyte of interest in human urine. The approach taken to address the issue was to use standards and quality controls to mimic the study samples and use Tween-80 (0.5%) to retrieve the adsorbed analyte.

Quantitative determination of BAF312, a S1P-R modulator, in human urine by LC-MS/MS: prevention and recovery of lost analyte due to container surface adsorption.

Analyte loss due to non-specific binding, especially container surface adsorption, is not uncommon in the quantitative analysis of urine samples. In developing a sensitive LC-MS/MS method for the determination of a drug candidate, BAF312, in human urine, a simple procedure was outlined for identification, confirmation and prevention of analyte non-specific binding to a container surface and to recover the 'non-specific loss' of an analyte, if no transfer has occurred to the original urine samples. Non-specific binding or container surface adsorption can be quickly identified by using freshly spiked urine calibration standards and pre-pooled QC samples during a LC-MS/MS feasibility run.

Simultaneous determination of midazolam and 1'-hydroxymidazolam in human plasma by liquid chromatography with tandem mass spectrometry.

A sensitive and simple liquid chromatography-tandem mass spectrometry method for the determination of midazolam and 1'-hydroxymidazolam in human plasma has been developed and validated with a dynamic range of 0.1-250 ng/mL. The analysis was based on semi-automated liquid-liquid extraction followed by evaporation of the extraction solvent, reconstitution and chromatography on a reversed-phase C(18) column.

Simultaneous determination of ribavirin and ribavirin base in monkey plasma by high performance liquid chromatography with tandem mass spectrometry.

For the first time, a liquid chromatographic method with tandem mass spectrometric detection (LC-MS/MS) for the simultaneous determination of ribavirin and rabavirin base was developed and validated over the concentration range of 10-5,000 ng/ml, respectively, using a 0.025 ml monkey plasma sample. Ribavirin, ribavirin base, and the internal standards were extracted from monkey plasma via protein precipitation.

Tolerability of cyclosphosphamide and methotrexate induction immunosuppression in nonhuman primates.

Transplantation in nonhuman primates, in particular using solid organs from porcine donors, requires an efficacious induction immunosuppression. Besides biologicals, the low molecular weight drugs used include cyclophosphamide (CyP) and methotrexate (MTX). As these compounds generally have a narrow therapeutic window, we performed tolerability studies in baboons and cynomolgus monkeys, with/without maintenance immunosuppressants such as cyclosporine A, everolimus, mycophenolate sodium and FTY720.

Reference values for clinical chemistry and clinical hematology parameters in cynomolgus monkeys.

Background: In vivo xenotransplantation modeling in large animal species is often performed in nonhuman primates, including baboons. For proper data interpretation, reference values for clinical chemistry and hematology are required.

Methods: These values are available from baseline levels in animals subjected to tolerability/pharmacokinetic studies.

Reference values for clinical chemistry and clinical hematology parameters in baboons.

Background: In vivo xenotransplantation modeling in large animal species is often performed in nonhuman primates, including baboons. For proper data interpretation, reference values for clinical chemistry and hematology are required.

Methods: These values are available from baseline levels in animals subjected to tolerability/pharmacokinetic studies.

Pharmacokinetics of nateglinide in renally impaired diabetic patients.

Treatment of hyperglycemia in patients with diabetes mellitus and renal insufficiency is complicated by altered pharmacokinetics of hypoglycemic agents. This study evaluated the pharmacokinetic profile and safety of nateglinide, an amino acid derivative that improves early phase insulin secretion and reduces mealtime glucose excursions. This open-label, single-dose, two-center study included patients (mean age = 57 +/- 10 years) with type 1 or 2 diabetes with impaired renal function (IRF) (n = 10) or with renal failure undergoing hemodialysis (n = 10).