Basic lipophilic drugs such as propranolol and lidocaine are strongly bound by α1-acid glycoprotein, also called orosomucoid. Although the liver is known to rapidly clear plasma protein-bound propranolol or lidocaine, it is generally regarded that peripheral tissues, such as brain or heart, are only exposed to the small fraction of drug that is free or dialyzable in vitro. The “free drug” hypothesis is subjected to direct empiric testing in the present studies using human sera and an in vivo rat brain paradigm.
William M. Pardridge, Roland Sakiyama, Gary Fierer