77,90 A case report confirmed the ability of paroxetine to inhibit the PGP in the BBB and in the kidney, causing digitalis intoxication with delirium, visual hallucinations, and disorientation.78

However, specific data from in vivo studies, substrate specificity, and inhibition or induction potential of psychiatric and neurological medication are still lacking. Examples related to drugdrug interaction at the membrane transporter level are illustrated in Table II. Table II. Examples of drug-drug interactions involving drug transporters. MDR, multidrug resistance; CNS, centra! nervous system; OCT, organic cation Inhibitors,research,lifescience,medical transporter; OATP, organic anion transporting peptide; OAT, organic ion transporter. Discussion In vitro and in vivo studies show that, drug carriers are expressed in the BBB and in the CSB. They represent major determinants of toxicity and clinical outcome related to drug response. Understanding the functional significance of membrane transporters in the BBB and in the CSB provides further Inhibitors,research,lifescience,medical opportunities to improve drug delivery to the CNS. We propose that the role of transporter proteins should be studied at, an early stage of CNS drug development, as there are in vitro methods such as cell cultures to achieve this purpose. Knockout, animals are valuable in Inhibitors,research,lifescience,medical vivo models,

but, in vivo methods in humans are few. Direct in vivo determinations of Inhibitors,research,lifescience,medical drug concentration and effective transporter function into the brain remain particularly challenging, as invasive techniques are necessary. Neuroirmaging techniques should be helpful, since molecules can be measured by positron emission tomography (PET) or by magnetic resonance imaging spectrometry. For example, the latter can be used to assess the pharmacokinetics of Inhibitors,research,lifescience,medical some fluoride-containing molecules in the brain. Although several members of the membrane transporters present in the BBB have been characterized in detail, numerous 5-FU cost questions remain open. Firstly, the determination of detailed tissue expressions and in vivo studies

of carriers with better specificity are required to target more efficiently therapeutic agents into the CNS and into other organs. Secondly, in order to enhance the potential clinical implications of drug transporter polymorphisms and interactions, Sclareol the development of specific inductors and inhibitors may represent, promising strategies. Thirdly, future delivery procedures include the use of prodrugs, drug-targeting vector conjugates, or liposomes tagged with targeting vectors to elude physiological barriers. Drug transporter protein studies provide insight into the mechanisms of resistance, treatment failure, and interindividual response to neurological and psychiatric medication. Membrane transporter proteins arc not only CNS gatekeepers, but represent determinant partners in CNS drug development, strategies.