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34 Cards in this Set
- Front
- Back
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Lipid-water partition coefficient
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Number means that it is X times more fat-soluble than water-soluble.
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A compound is ionized in...
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the opposite pH.
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In overdose, you sample for acidic drugs in...
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the blood.
and basic drugs in the stomach. (because they are charged in these compartments and can not get out of them) |
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Active transport
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Against [] gradient.
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Facilitated transport
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Similar to active transport but not energy-dependent. It is [] dependent.
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Ion-pair transport
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Highly ionized drugs get across membranes by finding a partner like a plasma protein.
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Benefits of sublingual or rectal/suppositories
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Avoid liver first pass metabolism.
Also with rectal, good for patients who are vomiting. |
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Stomach
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Only weak acids can be absorbed there, such as acetominophen.
Can get ion trapping of weak bases that are absorbed back from the blood into the stomach (changes from non-ionized to ionized and now it can't get out). |
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Where in Small intestine are most drugs absorbed?
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Most drugs absorbed in proximal jejunum.
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IM or SC
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Can do big volumes without the issue of IVs
But there is the issue of pain, local necrosis, etc. |
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IV
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Direct to blood. Great for drugs with narrow TI or poor absorption.
Easy to OD with this rt. Can't remove the drug or block or slow its absorption. |
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Only ___% is usually available as a free drug
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1-2%. So changing the binding to albumin or another protein by 1% will DOUBLE the amount of available drug!!!
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Charge on albumin
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- net, but can bind both + and - charged drugs.
Can bind hydrophobic drugs (high partition coeff) at lipophilic sites. |
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Lipophilic drugs can cross...
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BBB, BTestesB, placental barrier.
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First order kinetics
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A constant fraction of the drug is being eliminated.
(V. common) |
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0 order kinetics
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A constant AMOUNT of drug is removed over time.
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2-compartment model - what does alpha and beta represent?
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Alpha - Redistribution to the peripheral compartment (which is often larger)
Beta - Elimination after equilibrium is reached. |
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Alpha half life in a 2 compartment model
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DOES NOT REPRESENT CLEARANCE!!!
It is just the redistribution phase. The beta half-life tells you the actual elimination from the body. |
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Volume of distribution
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The volume of the compartment that contains the drug.
In a two compartment model, this is the central compartment (the plasma usually) It is a calculated value, and often does not correspond to actual physiological space. |
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Half-life is dependent on which factors?
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Volume of distribution and clearance.
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Clearance in a two compartment model
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It will initially look quite high, but that is just the redistribution.
It is relatively low once equilibrium is reached. |
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What does clearance really represent?
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Not the amount of drug removed, but the portion of the compartment (usually plasma) that has been cleared of drug per unit time.
So total systemic clear takes into account of the organs involved (e.g. kidney, liver, plasma, etc). |
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Shape of curves for drugs
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Usually identical, regardless of the dose.
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F (fractional dose)
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AUCoral/AUCiv
This allows for accurate dosing. |
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Steady state concentration (AKA Css) is dependent on...
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Infusion rate, Ko, and the clearance.
Usually takes 4 half-lives to achieve this. Or you can use a loading dose then switch to maintenance dose. But the downside of this is toxicity. |
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D* (AKA loading dose)
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To avoid the time to steady-state.
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Time to steady state is dependent on...
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Only the rate of elimination
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Dosing schedule should be equal to..
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the half-life. So there will be a 50% fluctuation in the peak concentration.
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Half life formula
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.693(volume of dist/clearance)
or .693/Kel |
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Volume of distribution formula
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loading dose / steady state concentration
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Clearance rate formula
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Elimination constant (Kel) * Vd
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F(oral) formula
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AUCoral/AUCiv
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Loading dose formula
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Steady state conc (Css) * Vd
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Maintenance dose formula
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Steady state conc (Css) * Vd * Kel
or Steady state conc (Css) * clearance |
