Pharmacokinetics 3 Flashcards
How can the steady state concentration be determined?
(BioavailabilityDose)/(Dosage Interval Clearance)
This is an average steady state concentration as in reality the concentration will fluctuate inbetween doses
What factors can be changed to change the steady state concentration achieved in the patient?
Dose and dosage interval
What is the effect of giving a lower dose of drug more frequently?
Causes a more stable steady state concentration (lower peak:trough ratio)
What is the effect of giving a dose of a drug once every halflife?
The peak to trough ratio will not go much greater than 2
What is the difference between the one and two compartment models?
Both models follow first order kinetics, however two compartment models assume there is a compartment aside from the central compartment…???
What are the effects of drugs that follow zero order kinetics?
The half life is dependent on concentration with a constant amount being eliminated per unit time until the eliminating mechanisms are saturated in which case there is an enormous increase in steady state concentration with increasing dose
What is a drug that follows zero order kinetics?
Ethanol, Phenytoin, Salicylate
What equation is used to describe the relationship between half-life and concentration for drugs that follow zero-order kinetics?
The Michaelis-Menten Equation
Elim Rate= Vmax *C/ (Km+C)
What equation can be used to determine the steady state concentration for drugs that follow zero order kinetics?
Steady State concentration= Km *Rate In/ (Vmax - Rate In)
Why might drug effect follow a different time-course from plasma concentration?
Relationship between concentration and effect is typically non-linear
The observed pharmacological effect may be indirect and take time to develop
Drug at the site of action may not be in equilibrium with drug in plasma
