Dried blood spot UHPLC-MS/MS analysis of oseltamivir and oseltamivircarboxylate--a validated assay for the clinic

The neuraminidase inhibitor oseltamivir (Tamiflu®) is currently the first-line therapy for patients with influenza virus infection. Common analysis of the prodrug and its active metabolite oseltamivircarboxylate is determined via extraction from plasma. Compared with these assays, dried blood spot (DBS) analysis provides several advantages, including a minimum sample volume required for the measurement of drugs in whole blood. Samples can easily be obtained via a simple, non-invasive finger or heel prick. Mainly, these characteristics make DBS an ideal tool for pediatrics and to measure multiple time points such as those needed in therapeutic drug monitoring or pharmacokinetic studies. Additionally, DBS sample preparation, stability, and storage are usually most convenient. In the present work, we developed and fully validated a DBS assay for the simultaneous determination of oseltamivir and oseltamivircarboxylate concentrations in human whole blood. We demonstrate the simplicity of DBS sample preparation, and a fast, accurate and reproducible analysis using ultra high-performance liquid chromatography coupled to a triple quadrupole mass spectrometer. A thorough validation on the basis of the most recent FDA guidelines for bioanalytical method validation showed that the method is selective, precise, and accurate (≤15% RSD), and sensitive over the relevant clinical range of 5–1,500 ng/mL for oseltamivir and 20–1,500 ng/mL for the oseltamivircarboxylate metabolite. As a proof of concept, oseltamivir and oseltamivircarboxylate levels were determined in DBS obtained from healthy volunteers who received a single oral dose of Tamiflu®.

GlaxoSmithKline’s experience of incurred sample reanalysis for dried blood spot samples

Dried blood spots are becoming a popular alternative to plasma for many different applications. This has been driven by animal ethics but also by ease of use and cost savings. Recent regulatory guidance now has a requirement for incurred sample reanalysis. This article details three examples of incurred sample reanalysis using dried blood spot samples.

Utilization of dried blood spots within drug discovery: modification of a standard DiLab® AccuSampler® to facilitate automatic dried blood spot sampling

The use of dried blood spots (DBS) in preclinical studies has seen an enormous increase over the past two years. Despite its positive impact on the 3Rs (reduce, replace and refine), its uptake in exploratory drug discovery has been limited due mainly to protracted method development time in bioanalysis but also the need for small volumes (<20 μL) to be sampled manually. Automatic blood sampling technology such as the DiLab® AccuSampler® is widely used in drug discovery to facilitate exploratory rodent-based pharmacokinetic and pharmacokinetic/pharmacodynamic studies with minimal animal handling. Propranolol was orally administered to a Han-Wistar rat attached to either a standard DiLab® AccuSampler® or a retrofitted unit designed to directly collect the DBS samples. In all, 50 or 20 μL blood samples were then collected via the standard or retrofitted unit, respectively, at six timepoints over a 7 h period. After drying and storage the DBS samples were analysed for propranolol via liquid chromatography-mass spectrometry. In this report we demonstrate that a standard DiLab® AccuSampler® can be easily retrofitted to facilitate automatic dried blood spot sampling and that time–concentration data generated from these samples are equivalent to that from manually spotted samples.

The rationality for using prodrug approach in drug discovery programs for new xenobiotics: opportunities and challenges

The concept of prodrugs has been successfully executed for life cycle management options of several approved drugs and drugs in development. In addition to imparting ideal biopharmaceutical properties, such as solubility, permeability and lipophilicity, some prodrug concepts have also enabled site-specific drug delivery, prolonged the duration of therapeutic effect and improved therapeutic index. The strategic inclusion of prodrug concept during drug discovery and early development process brings in some unique challenges. The communication provides balanced perspectives on the rational use and challenges of prodrug concept during the drug discovery and development process.

Determination of oseltamivir (Tamiflu®) and oseltamivir carboxylate in dried blood spots using offline or online extraction

Background: Using dried blood spots (DBS) for quantitation of the antiviral drug oseltamivir (Tamiflu®), an ester prodrug, and its active metabolite oseltamivir carboxylate could provide ethical and logistic benefits. Hence, its feasibility was investigated using a previously developed column-switching LC–MS/MS method. Results: Sensitivity, precision and accuracy in DBS were comparable to standard plasma assays. Chemically treated cards provided enhanced ex vivo stability of the ester prodrug in rodent blood. Online extraction was realized using the manual TLC–MS interface or the fully automated Sample Card and Prep system. Rat pharmacokinetic study data showed good correlation between plasma, liquid blood and DBS. Conclusion: From a bioanalytical perspective, DBS is potentially suited for Tamiflu analysis in animals and humans. Automation of the process by online DBS extraction promises workload reduction and throughput increase.