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Flashcards in Equations (1) Deck (9):
1

What is the equation for Volume of Distribution?

where C = concentration of drug in blood/plasma

Amount of drug in body = Dose administered

2

What is the equation for Clearance?  What is the unit most commonly used for Clearance?

where C = concentration of drug in blood/plasma

Units for Clearance: mL/min

Clearance is the amount of plasma cleared of the drug per unit time.

3

What is the equation for Rate of Elimination?

where CL = Clearance and C = concentration of drug in blood/plasma

4

What is the equation for Half-life?

where V = volume of distibution and CL = clearance

5

What is the equation for Hepatic Extraction Ratio?

where ER = extraction ratio, Q = hepatic blood flow

6

Keeping in mind the equation for the rate of Elimination, what is the equation for the Maintenance Dose in an IV infusion?

where ss = steady state, CL = clearance, TC = target concentration

7

If you switched from an IV infusion to an oral dosing regimen, how would you alter the "dosing rate" that you would use in your equations?

where Dosing Rate = the rate used for IV infusions, F = bioavailability

8

If a patient is on an IV infusion, and you halved the target concentration, how would this affect the infusion rate?

This would simply halve the infusion rate.  Re-arranging the equation, it is:

Target Concentration = "Rate in" / Clearance

9

Patients A and B are both receiving an IV infusion of lidocaine, and both require the same target concentration at steady state.  However, Patient B has renal disease, and so the clearance is half that of Patient A.  How should these two patients' infusion rates differ?

Remember the equation:

Target Concentration = "Rate in" / Clearance

So Patient B's infusion rate should be half that of Patient A.

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