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10 Cards in this Set
- Front
- Back
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What are the factors affecting distribution?
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Rate of distribution
Extent of distribution
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What is the equation that defines the amount of drug in tissue? |
Amount in tissue = VT . CT = VT . Kpb . CV Kpb refers to the tissue to blood distribution equilibrium ratio, i.e. CT ÷ CV |
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What is kT?
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kT is the fractional rate of leaving the tissue, also known as the distribution rate constant. kT = rate of leaving ÷ amount in tissue = (Q / VT) ÷ Kpb |
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What is the equation that defines the distribution half-life? |
t1/2 = ln2/k = ln 2 . (Kpb ÷ Q/VT) |
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The greater the partitioning of a drug into the tissue, ____. |
The longer it will take for the distribution equilibrium to be reached (i.e. distribution half-life will be longer). |
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The lower the blood flow into the tissue, ____. |
The longer it will take for the distribution equilibrium to be reached (i.e. distribution half-life will be longer. |
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What is the definition of apparent volume of distribution? |
The apparent volume of distribution (V) of a drug is the fluid volume in which a drug seems to be distributed to account for its plasma concentration. |
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How is V determined? |
V = Dose (mg) / C0 (mg/L) * C0 is extrapolated from a log Conc vs time graph. |
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How is V used to plan a dosage regimen?
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Loading dose = C.V / F
CSS = Dose.F / C.k.t where k is the elimination rate constant and t is the dosing interval |
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How is V used to relate the half-life of the drug to its clearance? |
CLtotal = V . k = V . (ln2 ÷ t1/2) |
