Pharmacology: Pharmacokinetics + Drug Deposition Flashcards
What is pharmacodynamics?
What a drug does to the body
What is pharmacokinetics?
What the body does to the drug
What is efficacy?
Ability of an agonist to provoke a response
Greater the efficacy, the greater the response
What is affinity?
The strength of association between agonist + receptor
What is pka?
The pH at which 50% of a drug is ionised and 50% is unionised
What is EC50?
Concentration of agonist that results in half maximal response
Do acidic drugs become more or less ionised in acidic environments?
Less ionised
What facilitates the absorption of weak acids?
The stomach lumen
Why must benzylpenicllin be given IV?
It is unstable in the acidic environment of the stomach
What is the pH of the duodenum?
neutral
What is the pH in the jejunum/ilieum?
Slightly alkaline
What is the volume of distribution (Vd)?
Volume in which a drug is dissolved
What does a Vd of
The drug is contained in the vascular compartment
What does a Vd of
Drug is contained in extracellular water
What does a Vd of >15L indicate?
The drug is in total body water
What is the minimum effective concentration (MEC)?
The concentration a drug must reach to have an effect
What is the maximum tolerated concentration (MTC)?
The drug concentration that must not be exceeded to prevent toxic effects
What is the therapeutic window?
Range of concentrations that can be used
What value of therapeutic window is classed as safe?
> 10
What is 1st order kinetics?
The rate of elimination (Kel) is directly proportional to drug concentration
What is 0 order kinetics?
Rate of elimination is constant and not determined by drug concentration
Which drugs exhibit 0 order kinetics?
Anti-epileptic drugs
What is Kel’s relationship with half life?
It is inversely proportional to half life
How does an increase in Vd affect Kel?
Decreases Kel
What does Css stand for?
Steady state concentration
What determines Css?
Half life
