Exam 1 - Pharmacokinetics Flashcards
Steady State Concentration
Constant serum concentration that is achieved when rate of drug administration = rate of drug metabolism/excretion
What is steady state concentration used for?
Assess patient response, make new decisions
Linear pharmacokinetics
Steady state concentrations increase/decrease proportionally according to dose. Example: Vancomycin, procainamide
Linear pharmacokinetics - not applicable when?
Patient has renal failure, organ failure, etc.
Non-linear pharmacokinetics
Steady state concentrations change in disproportionate fashion after dose is changed
Valproic acid, carbamazepine, phenytoin have what type of pharmacokinetics?
Non-linear
Saturable or Michaelis-Menten Pharmacokinetics
Steady state concentration increases more than expected after dose increase. Number of drug molecules overwhelms enzymes ability to metabolize drug
Half life
Time required for serum concentrations to decrease 50% during elimination phase after absorption/distribution are complete
How long does it take to reach steady-state concentrations during continuous dosing?
3-5 half lives
A faster clearance will cause a _____ half life
Shorter (if kidney function picks up, half life will be shorter)
Larger volume of distribution will result in ____ half life
Longer (amiodarone) or shorter (propofol)
Bioavailability
Fraction of administered drug that is delivered to systemic circulation
Bioavailability of IV drugs
100%
Central compartment
Plasma
Peripheral compartment
Tissues
Multi compartment model
Body is central compartment where drug is administered, peripheral compartment is where drug is distributed - curvature will be non linear.
Back end kinetics
Describes how plasma drug concentrations decrease once a continuous infusion is terminated
Decrement time
Predicts the time required to reach a certain plasma concentration once infusion is terminated
If decrement time is 50%, what is another name?
Context sensitive half time
Longer infusion will result in ______ decrement time
Prolonged — due to increased accumulation
Effect site
Biophase - drugs exert their biological effect at this site
Biophase
Body compartment in which receptor sites reside
Pharmacokinetics
Relationship between the drug administration and drug concentration at the site of action. Movement of drug throughout the body
Pharmacokinetics principles
ADME - Absorption, distribution metabolism, excretion/elimination
Magnitude of drug effect and duration of action is affected by?
Absorption
Percent of drug that reaches systemic circulation
Bioavailability
Volume of distribution equation
Dose divided by concentration
A larger person will have a _______ volume of distribution
Larger
A smaller person will have a _______ volume of distribution
Smaller
When does volume of distribution increase?
When drugs move from blood to tissues
As volume of distribution increases due to drugs moving from blood to tissues, what will happen to blood concentration?
Decreases