Pharmacokinetics - Drug absorption and Transport of drugs across biological membranes
Transport of drugs across biological membranes All pharmacokinetic processes involved transport of the drug across biological membranes. Biological Membrane Biological membranes may be viewed as mosaics of functional units composed of lipoprotein complex. Most membranes are composed of a fundamental structure called the unit membrane or plasma membrane. This boundary, which is 80 to 100 A° thick, surrounds single cell and nuclei. More complex barriers such as the intestinal epithelia and the skin are composed of multiples of this functional structure. The plasma membrane consists of a bilayer of amphipathic lipids with their hydrocarbon chains oriented inward to form a continuous hydrophobic phase and their hydrophilic heads oriented outward. Individual lipid molecules in the bilayer can move laterally, endowing the membrane with fluidity, flexibility, high electrical resistance and relative impermeability to highly polar molecules. The known fluidity of the phospholipids i
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