Pharmacokinetics and Pharmacodynamics Flashcards
Mathematical description of plasma concentration-time course
Pharmacokinetics
What are components of the dosage regimen?
Dosage
Route of administration
Frequency
Duration of administration
What is an optimum dosage regimen?
Effective and Nontoxic (within the therapeutic window)
Without prolonged drug residues in tissue of food animals
Time to peak plasma concentration
Rate of absorption (tmax)
_______________ is the fraction of the dose which reaches the systemic circulation intact
Systemic bioavailability
How is systemic bioavailability calculated?
Systemic bioavailability (F%)= (AUC extravascular x100) / (AUC IV)
AUC= area under the plasma concentration-time curve
What is the one-compartment model?
All tissues and organs that the drug penetrates (good enough reason to use penetrate???) behave as if they were in ready equilibrium with the blood
What is the two-compartment model?
Peripheral and central compartments behave differently
Initial decent (distribution phase): distribution from central compartment to peripheral compartment
Second decent (elimination phase): metabolism and excretion of the drug
_________________ is estimated by the distribution phase half-time(t1/2a) in the two compartment model
Rate of distribution
_______________ is measured by the apparent volume of distribution
Extent of distribution (Vd)
what is the volume of fluid which would be required to contain the amount of the drug in the body if it were uniformly distributed, and the concentration in that fluid was equal to the concentration of the plasma
Apparent volume of distribution (Vd)
How is apparent volume of distribution calculated?
IV: Vd (L/kg)= amount of drug in body (Dose)/ plasma drug concentration (cp)
Extravascular: Vd= dose x F% / Cp
Vd < 1L/kg means?
Drug has limited distribution (tends to stay in plasma)
Vd = 1L/kg means?
Drug has a wide distribution (concentration of drug in tissue is the same as the plasma)
Vd > 1L/kg means?
Drug has a very wide distribution (concentration is greater in the tissue than plasma)
___________ is the time required for the body to eliminate one-half of the drug it contains
Half life
Elimination in first order kinetics means?
Rate of removal of drug from the plasma is proportional to concentration present at a given time (a constant percent of drug is eliminated per unit time)
What is elimination by zero-order kinetics?
Rate of elimination remains constant regardless of the amount of body in the drug (a constant amount of drug is eliminated per unit time)
Aspirin in cats follows (first/zero) order kinetics of elimination ?
Zero
What determines the rate at which plasma concentration of a drug rises during constant IV infusion to attain a steady state concentration ?
Half life
Plasma concentration when the maintenance rate of drug administration is equal to the rate of elimination
Steady state plasma concentration / plateau
How many half life’s does it take for a drug to reach 90% of the steady-state concentration
3.3
What percent of the steady state concentration is achieved after 4 half lives ?
93.75%
T/F: A faster rate of infusion will change the time needed to achieve steady state concentration
False
The drug will have a higher steady state concentration if the rate of infusion is faster
Rate of drug elimination from the body, by all routes, relative to the concentration of drug in the plasma
Total body clearance
CL(B) = CL (r) + CL (nr)
What is plasma clearance?
Volume of plasma cleared of the drug per unit time
How is plasma clearance calculated?
CL (p)= rate of elimination(mg/min)/ plasma drug concentration (mg/mL)
How is rate of elimination calculated?
Rate of elimination (mg/min) = urine flow (mL/min) x concentration of drug in urine (mg/mL)