Clearance and bioavailability study through arterio-venous drug concentrations relationship

Venous plasma drug concentrations are routinely monitored in order to determine pharmacokinetic parameters or to establish relationships with drug pharmacodynamic and clinical effects. Arterial drug concentration is higher than the respective venous concentration during the period where drug input of the substance predominates, whereas venous drug concentration is higher during the long period where drug elimination becomes the main process. This arterial-venous difference responds to current bioavailability and clearance of the drug-individual systems. Following the vein/artery plasma drug concentration ratio at a non-eliminating organ it is possible to monitor both parameters time by time. This way of following up the pharmacokinetic systems allows us to detect any changes in drug absorption or disposition more efficiently, without the need of a long period of time and regardless the duration of such system modification.