MCPHS PHARMACOKINETICS EXAM QUESTIONS AND ANSWERS WIT COMPLETE SOLUTIONS VERIFIED LATEST UPDATE
Describe drug absorption
Occurs when a drug is not injected directly into the vein(IV). The drug needs to pass through the body and get to the bloodstream. Factors that affect GI motility, surface ar...
Occurs when a drug is not injected directly into the vein(IV). The drug needs to pass through the body
and get to the bloodstream. Factors that affect GI motility, surface area, the dosage form
used(disintegrate, dissolve, absorb), and physicochemical properties(lipid solubility, size, matter...).
Describe absorption process
The drug is administered in one way or another Part A is the therapeutic action(drug) B is non-
therapeutic (moiety). A+B is the molecular form of the drug. To a count, for the inactive drug a salt factor
is in place(A/(A+B)). Once processed to GI tract absorption starts(Dgi=A+B). The amount that becomes
bioavailable (Db) relies on the product of the salt factor(S), the fraction of drug absorbed(F), and the
amount of drug in the GI tract(Dgi).
Zero order absorption
Carrier molecules get saturated, or fixed amounts released, aka modified release drug. Based on the data
collected. Absorption rate constant is k0.
First order absorption
,Most absorption, faster absorption. Absorption rate constant k. The rate of this absorption is equal to
the rate at which the drug is absorbed minus the rate of elimination. When t is large there is no
absorption.
Wagner-Nelson method
Determines fraction of un-absorbed drug k and ka in a single compartment.
Loo-Riegelman method
Determines fraction of un-absorbed drug k and ka, assumes a double compartment model. Drug needs
to be given by IV and by PO in order to determine all the parameters. Need to determine transfer
constants before use k12 k21.
Cmax, Tmax, AUC relationship
ka↑ k≡ CMAX↑ TMAX↓ AUC ≡
k↑ ka≡ CMAX↓ TMAX↓ AUC ↓
Flip flop Ka and K during pharmacokinetic data analysis
normally ka>k in this instance ka<k. Happens when estimated from oral absorption. Occurs with fast
elimination k>0.69 or short t 1/2 not good for PO. To ensure this doesn't happen also give by IV. can also
happen in modified doses.
Method of residuals
Plot of Cp used to determine ka. Can be determined using the feathering technique. Extrapolate the lines
and the difference from the two lines is the residual line-ka/2.3
distribution phase is more rappid than the elimination phase
Main routes of drug elimination 9
, l9-10 Primary route is kidneys, but it can also be through lungs, sweat, and breast milk. Bio-
transformation or removal of unchanged drug
Principle of Superposition
To lay something on top of another thing. Multiple doses on top of each other to increase the total dose.
More doses the higher the concentration, keeps rising until it reaches a steady state. Sum of all the drug
in the system at that time. Each individual has a max but multiple doses can sum up to a SS and higher
conc.
Drug Accumulation
Mutiple dosing that is intended to keep plasma levels within the thereputic window. Early doses have no
pharmocokinetic effect on the later doses. Only superimposed on those of the earlier doses. Entire single
dose administration is equal to any dosing interval at steady state in a multiple dosing case. Peak
concentration will continue to rise until SS is reached. Can predict from a single dose administration.
Even with slight alter in T prediction will still hold.
Drug accumulation half life
depends on t1/2 elimination NOT ꚍ NOT Dose
Plasma drug concentrations IV one compartment
Cmax, Cmin, Cav, Cp, Cp∞ Can be repeated to help better tolerate
Plasma drug concentrations non-compliance scenarios
Missed: tmiss, the more recent a tmiss the greater effect it will have on the current plasma conc. tmiss
greater than 5 t1/2 should be omitted(minimal impact).
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