Unbound compound concentrations and the free drug hypothesis

2 Unbound compound concentrations and the free drug hypothesis 

Based on the described neuroanatomy, the three key matrices for evaluating compound concentrations to determine the extent and/or rate of CNS penetration are blood, CSF, and brain tissue. Due to the nearly universal analysis of plasma to determine systemic concentrations of small molecules, total plasma compound concentration (Cp) will henceforth be substituted for total blood concentration, which is the product of Cp and compound blood-to-plasma ratio. 

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