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80 Cards in this Set
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- Back
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What relates drug concentration to rate of drug elimination?
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Clearance.
Rate of Elimination= Cl x C |
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Methods of Elimination
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excretion
metabolism |
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Which method of elimination is most prevalent for drugs?
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metabolism
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Name routes of excretion. (5)
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bile
urine sweat breast milk breath |
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_________ can be described as the loss of drug across an organ of elimination.
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Clearance.
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_______ is determined from the total exposure(AUC) following an IV dose.
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Total Clearance
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__________ can be determined from the fraction excreted unchanged and total clearance.
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Renal Clearance.
Cl (renal)= Fe x Cl |
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True or False.
Rate and extent of metabolism can be measured directly. |
False. It can rarely be measured directly.
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How can hepatic clearance be estimated?
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Cl t = Cl r + Cl h
Cl h = (1-Fe) x Cl |
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What is the main organ for metabolism?
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Liver
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_______ excretes drugs into the bile, and then are removed
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Liver
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True or False
A drug with a high extraction ratio will be mostly eliminated. |
True
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Whats does an extraction ration indicate?
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effectiveness of elimination
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What number value(s) indicates a high ratio of extraction?
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0.7-1.0
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A drug has an extraction ration 0.86, what is this drugs limiting factor?
What does its rate of elimination depend on? |
perusion bc this drug has a high extraction rate.
r.o.e.depends on concentration. |
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True or False.
A drug has a high Extraction ratio . Clearance depends on plasma protein binding. |
False.
A drug with a low E.R. is dependent of plasma protein binding. |
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What number value(s) indicate a low extraction ratio?
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0- <0.7
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For a drug with a low extraction ration, clearance depends on___________.
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plasma protein binding and the drugs affinity for hepatocytes.
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________ can be described when the unbound concentration of a drug is the same as entering and leaving an organ
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Low extraction rate.
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True or False.
A drug with a low extraction ratio is perfusion limited. |
False. It is not perfusion limited.
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What portion of drug can be eliminated by the liver?
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unbound portion
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When a drug is perfusion limited, increasing the flow rate will___________ clearance.
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increase
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When a drug is not perfusion limited, increasing the flow rate will__________ clearance.
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have no effect
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What allows predictions in which clearance or e.r. is affected, and the expected change of direction?
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The Well-stirred model of hepatic clearance.
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T/F
Permeability can affect clearance. |
True.
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________ molecules have low permeability across membranes.
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Large and/or polar.
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T/F
Location of transporters can affect clearance |
True.
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Enterohepatic cycling is a component of __________.
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distribution.
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Describe enterohepatic cycling.
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drug--> bile--> bile duct--> SI--> possible reabsorbtion
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What is biliary clearance dependent on?
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B. C = ( bile flow)( conc. in bile)/ conc in plasma
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What is the functional unit of the kidneys?
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nephrons
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A drug present in the urine is dependent on these three processes.
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1. filtration
2. secretion 3. reabsorption |
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Which process(es) transfer the drug from lumen to bloodstream?
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reabsorption
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Which process(es) transfer the drug from bloodstream to the lumen?
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filtration
secretion |
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What is glomerular filtration?
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Passive diffusion of drug across the glomerulus.
(max 130ml/min) |
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What is tubular secretion?
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active secretion of drugs from blood to lumen ( urine excretion)
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What is tubular reabsorption?
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reabsorption of drugs from urine back into the blood.
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___________ is an endogenously produced compound that is neither bound to plasma proteins nor secreted and the entire filtered load is excreted into the urine.
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creatinine
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Why is creatinine clearance important?
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1. helps to id any renal complications
2. measures GFR 3. determines dosing of drugs |
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What is the most common measure of renal clearance?
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creatinine clearance ( CrCl)
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What is a normal creatinine clearance?
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120-130 ml/min
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What does the Cockcroft-Gault equation indicate?
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The CrCl---- the extent of GFR, and renal function.
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Which renal clearance process is being observed
Renal Clearance > Fraction of drug unbound x GFR |
Tubular Secretion
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Which renal clearance process is being observed
Renal Clearance <Fraction of drug unbound x GFR |
Tubular Reabsorption
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What is typically a pH of urine?
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7- neutral
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If the pH of urine rises, a drug that is a weak acid will be reabsorbed_______, and eliminated_______.
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less; more
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A basic drug that is polar will most likey be__________.
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eliminated. Only way it can be reabsorbed is if it is actively transported.
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A basic nonpolar drug that has a pka </= 7 will most likey be____________.
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Reabsorbed.
( renal clearance is low bc almost 100% is unionized, making it prone to reabsorption) |
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Drugs in the urine that are ionized will be ____________, while drugs that are unionized will be__________.
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eliminated; reabsorbed.
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Which route of administration typically has a higher c-max?
Oral or IV |
IV
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When looking at a CT curve for an oral drug, which two processes are equal at the peak?
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aborption and elimination
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_______occurs when the drug is absorbed by a saturable process
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Zero-order process
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_______occurs when a zero-order controlled release delivery system is used
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Zero-order process
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What is the limiting factor when absorption half-life is much shorter than elimination half-life
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Disposition rate
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What is the limitin factor when absorption half-life is much longer than elimination half-life?
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Absorption rate
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True or False.
When absorption rate is your limiting factor, than drug X could possibly be therapeuticly ineffective. |
True
(Why? -- think of CT curve. drug might not reach MEC) |
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True or False
Oral drug is rarely 100% bioavailable |
True
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What is T-max dependent on?
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Ka and K
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How would you define lag time?
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delay of absorption
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True or False.
K is typically less than Ka. |
True
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Which order process will you see a lag time?
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first order
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What things contribute to lag time?
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Slow tablet disintegration
Slow and/or poor drug dissolution from the dosage form Incomplete wetting of drug particles Poor formulation A delayed release formulation |
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What is the significance of an absoption rate constant?
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Designing multiple-dosage regimens
Prediction of peak and trough plasma drug concentrations Bioequivalence studies—comparing rates of absorption from chemically equivalent products |
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What is the significance of T-max?
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Determine the comparative bioavailability and/or bioequivalence
Determine the preferred route of drug administration and the desired dosage form for the patient Assess the onset of action |
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What is the significance of C-Max?
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Determine the comparative bioavailability and/or bioequivalence
Correlate with the pharmacological effect |
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What is an advantage of using an IV infusion?
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drug input can be stopped instantly if adverse effects occur
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What is a disadvantage of using an IV infusion?
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usually restricted to institutional settings
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This R.O.A should be used when the intent is to achieve and maintain a stable plasma concentration or amount in the body
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IV infusion
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With an IV infusion, duration of a constant-rate infusion is usually much ______ than the half-life of the drug
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longer
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___________provides precise and controlled systemic drug input
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IV infusion
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When looking at a CT curve, what does a plateau represent?
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steady state concentration.
( rate of infusion = rate of elimination |
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How is IV infusion different from IV bolus in terms of Co.
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IV infusion Co = 0. The concentration increases.
IV bolus Co = C-Max. The concentration decreases. |
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"rate in = rate out" represents
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steady state
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What are the only factors governing steady state concentration?
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the rate of infusion
the elimination rate |
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What factor controls the time it takes to get to the steady state concentration?
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half-life
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The ______the half-life the sooner the steady-state is reached.
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shorter
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The ______the half-life the more time it takes for the steady-state to be reached.
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longer
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Steady-state may be considered to be reached in ______half-lives
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3.3 ( 90% of plateau)
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T/F
The rate of infusion of a drug is sometimes changed during therapy because of excessive toxicity or an inadequate therapeutic response. |
True
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If you increase the infusion rate, you can increase _________, but __________ will not change.
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The amt of steady-state concentration; time it takes to get the steady state ( as it is dependent only on half-lfe)
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