PHAR 340 Lecture Notes - Lecture 11: Body Water, Extracellular Fluid, Biotransformation
23 Dec 2018
School
Department
Course
Professor
Document Summary
Gfr=130ml/min, drug is freely filtered, reabsorbed + not bound to protein. Rate of drug elim at any time prop [drug] at that time. Rate of elim is linear via filtration but logarithmic for enzymes/transporters (1st part of graph is linear and where most drugs are) Saturable so can be zero-order if [d] high. Body elim a fixed percentage of drug per unit time. Elim rate constant (ke): when drug is elim by 1st-order kinetics ke=0. 1/h= 10% of drug/hr logc=logco-ket/2. 303 initial drug conc=co. Half-life: t = time req for conc of drug to decr by 50%, constant for 1st-order elim. To reduce conc by half ln0. 5=-0. 693=-ket t =0. 693/ke. Assumes body= single compartment and drug uniformly distributed + rapidly relative to absorp + elim. Vd= v apparently necessary to contain the amount of drug if it were distributed homogenously at conc found in plasma. Total body water= 42 l, intracell=28l, extra=14l (3l intravascular, 11l interstitial fluid)
