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29 Cards in this Set
- Front
- Back
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What is drug disposition? |
How humans respond to drugs |
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What are the 4 parameters determining drug disposition (how humans respond to drugs)? |
1. Clearance 2. VD 3. Elimination half life 4. Bioavailability |
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Why is plasma a good site to measure drug concentrations? |
1. it is non-invasive 2. there is a good correlation between plasma concentration and therapeutic and toxic effects of drugs |
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Do we measure free drug concentration, protein bound drug concentration, or both? |
both. we measure both, it's easiest. |
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What does Cmax on the concentration time curve for oral administration represent? |
time point when rate of drug absorption = rate of drug elimination |
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Define the MEC |
MEC is the minimum effective concentration. It is the minimum concentration required for the drug to have a therapeutic effect. |
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Define duration |
Length of time the drug is above the MEC |
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Define toxic concentration |
concentrations which induce toxic side effects of the drug |
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define therapeutic range/window |
drug concentrations above the MEC but below the toxic concentration. the goal of pharmacotherapy is to attain plasma concentrations in the therapeutic range |
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What precautions are taken with drugs that have small therapeutic windows? |
Therapeutic monitoring. Trough blood samples must be taken, that is, a blood samples taken prior to the next dose of the drug. |
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What is lag time? |
Time it takes for drug to reach MEC |
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Rate of absorption determines _______ Amount of absorption determines ________ |
drug onset of action intensity of drug action |
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In intravenous injections, what rate is used against time, instead of absorption rate? |
infusion rate |
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what is steady state concentration? |
When infusion rate = elimination rate. The plasma concentration does not change over time. |
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Injection of IV Bolus follows what order kinetics? |
First. Rate of drug metabolism/elimination is dependent on drug concentration |
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How is steady state concentration achieved in repeated dosing? |
Steady state concentrations are achieved when the peak and trough concentrations are (relative to each other) the same between doses. |
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With regards to repeated dosing, what is the goal of pharmacotherapy. |
The goal of pharmacotherapy is for fluctuations at steady state to be within the therapeutic range |
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name and describe the 3 ways to reduce plasma concentration fluctuations |
1. use continuous IV infusions - allows constant drug levels (no peaks and troughs) 2. use depot preparations - allows drug to be absorbed slowly over time, minimizing peaks and troughs 3. Change dosing interval - smaller but more frequent doses minimize peaks and troughs better than larger but more spaced out doses |
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Define Clearance |
efficiency of irreversible drug elimination from the body. Volume of blood cleared per unit time (mL/min) |
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What is total clearance |
Sum of clearance by all routes of elimination (i.e. hepatic clearance + renal clearance, etc.) |
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What is the dosing rate equation |
Dosing rate = target plasma concentration x clearance |
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Define half life, and the half life equation. |
Time it takes for plasma concentrations to decrease to 50%
T1/2 = 0.693Vd / Clearance |
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What are the two reasons knowing a drug's half life is important |
1. It determines time it takes for the drug to reach steady state 2. It determines time it takes for drug levels to decline once administration has ceased |
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when the ______ dose of a drug is administered _________, it takes ____ half lives to reach steady state |
when the same dose of a drug is administered repeatedly, it takes 5 half lives to reach steady state concentration |
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time to steady state concentration is dependent/independent of the dose size, but actual steady state concentration is dependent/independent of the dose size |
time to steady state concentration is independent of the dose size, but actual steady state concentration is dependent of the dose size |
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if a drug has a particularily long half life, what can be done to reach steady state concentrations faster? |
A loading dose can be given. |
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What is the calculation for a loading dose? |
Loading dose = target plasma concentration * Vd |
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how many half lives does it take to remove most of a drug from the body? |
5 |
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How many half lives does it take to remove all the molecules of a drug from the body? Why is this important? |
9. This is important for those with allergies, as allergic reactions still occur when there are a couple of molecules in the system |
