BIOM20002 Lecture Notes - Lecture 34: Nonsteroidal Anti-Inflammatory Drug, Circulatory System, Drug Metabolism
Document Summary
Brain capillaries are "tight" - tight junction between brain capillary endothelial cells prevents pericellular passage. Also a blood testes barrier that is similar. To get from the blood to the brain, a drug has to cross the endothelium transcellularly. Brain endothelial cells also has transporters that actively pump drug out and back into blood. Organs with fenestrated capillaries (kidneys, intestines, liver) are readily accessible to all drugs. Organs with diffusionally-tight capillaries (brain, testes) are accessible mainly to lipid-soluble drugs. Mepyramine is lipid soluble, membrane permeant, diffuses into brain, inhibits histamine (an nt that causes alertness in brain). Fexofenadine: at ph 7. 4 (physiological ph) the carboxyl group becomes charged. Excluded from brain and works in periphery only, so doesn"t cause drowsiness. Some organs (kidneys, heart) get more blood flow than others (fat and resting muscle) If you inject a drug you see a lot of the drug will go to brain and other organs with large blood flow.
