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Terms in this set (23)
What is pharmacokinetics?
It is a branch of pharmacology dedicated to the determination of the fate of substances administered externally to a living organism.
What is the F value?
It is the bioavailability
How do you calculate the %bioavailability?
F x 100
How do you calculate the actual drug amount absorbed?
Dose x F
The presence of what can significantly change bioavailability?
The presence of food
How do you calulcated bioavailability?
F=AUC PO (any route)/ AUC IV
AUC=area under the curve
What is Vd?
Amount of drug in body (D x F)/ Cp0
D is dose
(Cp0 is plasma conc. @ time 0, determined from drug elimination curve)
*Volume of distribution is always in liters
How do you calculate the volume of distribution?
Vd=Loading dose (LD) / Therapeutic Cp
How do you calculate the loading dose?
LD=Vd x Cp (IV administration); for PO adm must divide by F value
In first order reactions, how is the pharmacokinetic rate related to the dosage?
Change in pharmacokinetic rate reaction proportional to dosage
Drugs have a fixed T1/2 (most drugs)
In zero order reactions, how it the pharmacokinetic rate related to the dosage?
Change in pharmacokinetic rate reactions not proportional to dosage
Drugs have no fixed T1/2.
These drugs in overdose accumulate significantly faster.
Which order of reaction has a half-life?
What is the half-life and how is it determined?
It is the time required to change the amount of drug in the body by one-half during elimination, not the duration of action.
What is the one-compartment model?
It is where the body is viewed as a single compartment.
For drugs that are water soluble.
Drug conc in different tissues not equal, but at equilibrium and proportional to Cp.
Drug conc in different tissues varies proportionately as Cp changes.
What is the two-compartment model?
Body viewed as 2 compartments based on distribution, blood flow, lipid solubility
Drugs always enter \ exit central compartment.
What are the two compartments described in the two-compartment model?
Central compartment - high blood flow, blood, brain, lungs, heart, liver, kidney
Peripheral compartment - low blood flow, tissues with inc % fat (skin, muscle, adipose); destination of lipid soluble drugs with large Vd .
What is drug clearance?
Rate at which drug is cleared from body, defined as volume of fluid (plasma) from which drug is removed in given time eg. mls / min or liters/hr
What is the equation for clearance?
CL=Vd x 0.7 / t1/2
CL has an inverse relationship with t1/2
Vd and T1/2 have a proportional relationship
Why is normal creatine clearance important?
Applies to drugs whose elimination depends on renal clearance
Corrected dose=normal dose x ratio (patients creatinine clearance/1—ml/min)
Plateau principle only applies to what order reactions?
Applies only to drugs following first order
Dosage and dosage interval must remain constant when determining Cpss.
Plateau is a function of what other principle?
How do you calculate the maintenance dose?
Maintenance dose = Cpss x CL x T/F (T: dosing)
How do you calculate the plasma serum concentration?
Cpss= Dose x F / (CL x T)
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