Physicochemical Profiling Services

Blood to Plasma Ratio

Understand the distribution of your compound between red blood cells and plasma using our blood to plasma ratio service.

Blood to plasma ratio determination is one of Cyprotex's in vitro ADME services. Cyprotex delivers consistent, high quality data with the flexibility to adapt protocols based on specific customer requirements.


Pharmacokinetic parameters are usually determined by analysis of drug concentrations in plasma rather than whole blood. In situations where there is a significant compound concentration difference between plasma and red blood cells, in vivo clearance estimates based on plasma will differ to those based on blood. Therefore, it’s important to understand the extent to which a compound partitions between plasma and red blood cells.


Blood to Plasma Ratio Assay Protocol

The blood to plasma ratio determines the concentration of a compound in whole blood compared to plasma, and provides an indication of drug binding to erythrocytes. Our blood to plasma ratio services are based on an adaptation of the method proposed by Yu et al.1 In brief, test compound is spiked into fresh heparinized whole blood, reference red blood cells and reference plasma; following the incubation period, the whole blood is centrifuged and both fractions of the whole blood (plasma and red blood cells) are analyzed by UPLC-MS/MS alongside the reference samples. Note, red blood cells are freeze thawed on three occasions to lyse. Cyprotex offers a blood to plasma ratio service for a wide range of species.


1) Yu S, Li S, Yang H, Lee F, Wu JT, Qian MG. A novel liquid chromatography/tandem mass spectrometry based depletion method for measuring red blood cell partitioning of pharmaceutical compounds in drug discovery. Rapid Commun. in Mass Sp. 2005, 19, 250-254


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Cyprotex enables and enhances the prediction of human exposure, clinical efficacy and toxicological outcome of a drug or chemical. By combining quality data from robust in vitro methods with contemporary in silico technology, we add value, context and relevance to the ADME-Tox data supplied to our partners in the pharmaceutical or chemical industries.