BIOL 1260 Lecture 11: Drug Distribution
2 Dec 2016
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Does it get to site of action: unless specialized area (cns, inner ear, eye, etc. usually not a problem. Net distribution from the plasma: diffusion-based. Drugs may bind to plasma proteins and macromolecules in tissues. Only free unbound drugs participate in diffusion, so binding to proteins in membrane holds the drugs in the plasma. Permeability of individual cell types: transporter-based. Generally only involves a small amount of drug. Assessment of extent: give a dose and distribution is essentially instantaneous into space the drug can access, measure cp and interpret use vd. Vd: ratio of the amount of drug in body (ab) and the cp at the same time (not physiological volume: vd = ab/cp, ex. give 80mg iv, so ab=80mg. 80mg/40l = 2mg/l vd = 80/2 = 40l if cp = 5mg/l vd = 80/5 = 16l: explanations for lower vd. Drug doesn"t distribute into full volume/can"t access all of it.
