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28 Cards in this Set
- Front
- Back
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How is the difference between a one vs a two compartment model determined?
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It is delineated only by the rapidity of tissue dissemination (ie by the rate of equilibration across all tissues)
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what is the equation for rate of elimination?
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Vel = kel*[A]
kel = elimination rate constant [A] = concnetration of drug at site |
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In a first order process what would happen to elimination rate if you double the concentration of drug?
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Elimination rate would also double by the equation Vel=kel*[A]
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How is the rate of elimination determined in a first order process?
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As concentration decreases the rate of elimination also decreases
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In zero order kinetics what type of drug absorption is occuring and what are some parameters associated with it?
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It is a transport typically active which utilizes carriers, energy, and can become saturated. Saturation is key to zero order kinetics because then its elimination or absorption rate is constant
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What is t1/2 and what does it mean?
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T1/2 is the half life of the drug and indicates the rate at which half of the drug will have been absorbed or eliminated.
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How can you calculate for T1/2 given the kel?
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T1/2 = 0.693/kel or
T1/2 = ln0.5 Vd/Clt |
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If on an a plot you see a break in an elimination curve that should be linear what does this imply?
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It indicates that there is a two compartment system at work.
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What would occur to the half life of a drug if the volume of distribution increases?
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The half life also increases! Remember equation
T1/2 = 0.5ln Vd/Clt |
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What does a lower kel indicate vs a higher kel? And how is that displayed on a log plot of elimination?
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lower kel is indicative of a longer half life while a shorter kel is indicative of a shorter half life. On a log plot you would see a line that slopes further than the other to indicate a lower kel.
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How do you calculate for volume of distribution of a drug?
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Concentration = grams of drug/volume --> C = X/V
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How is total body clearance calculated?
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ClT = Kel * Vd
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How is area under the curve calculated?
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ClT = Xo/AUC
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How is clearance combined from all the different compartments?
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Additive ie ClT = Clliver + Cl kidney + Cl other
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How is rate of entry of a drug calculated?
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Vin = Qblood * Cdrug in or
Vout = Qblood *C drug out |
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How would one calculate Velim?
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Velimination = Vin - Vout
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How is the extraction ratio calculated?
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(QCin - QCout) / QCin = E
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How do you calculate for clearance of the liver?
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Clliver = E*Qblood
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What is meant by intrinsic clearance?
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Maximum ability of drug to be eliminated by a specific organ
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What are the components of renal clearance?
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Glomerular filtration
Renal secretion tubular reabsorption Clr = Clgfr+CLs - Cltr |
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Because some compounds are bound to plasma proteins and not filtered how is renal clearance calculated for?
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Clr = Fu*GFR + Cls - Cltr
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What does a Clrenal > than GFR imply and what does a Clrenal < GFR imply?
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Clr < GFR Compound is being reabsorbed
Clr > GFR Compound is being excreted |
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What does bioavailability tell us?
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Fraction of the drug that reaches the systemic circulation
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How do you calculate the bioavailability ratio?
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AUC extra/ AUCiv = bioavailability
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How many half lives does it take to reach a steady state and about what percentage is this steady state?
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It takes about 4-5 half lives to reach steady state with about a 95-97% steady state concentration level.
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How do you calculate for steady state concentration?
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Css = Dose rate/ClT
Steady state conc = dose rate divided by total body clearance ClT = Kel * Vd can be substituted in for ClT |
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How much should the loading dose be?
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about 2x that of the maintenance dose
X* = Css * Vd |
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In drugs that undergo a first order process Css related to dose rate in what way?
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Css is directly proportional to the dose rate up to a point in which the enzymes are completely saturated.
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