Principles of Pharmacology Flashcards
Clearance
Definition
Volume of plasma from which the drug is eliminated per unit time
Oral bioavailability
Definition
The amount of drug that reaches the systemic circulation
Depends on absorption
Expressed as percentage of the IV dose
Partial Agonist
Definition
Binds and activates a receptor but cannot induce a maximal response even at full occupancy
NB. If given with a full agonist, it becomes antagonistic as it occupies some receptors which could otherwise be activated.
Partial agonists have decreased efficacy compared to full, but not necessarily decreased affinity
Zero Order Kinetics
A constant amount of drugs metabolised per unit time
(The rate of reaction is constant)
This means that metabolism can be saturated, after which any further addition of drug (even a tiny dose) can massively increase plasma concentration
Examples: alcohol, salicylates
First Order Kinetics
Rate of reaction is directly proportional to the concentration of one of the reactants
Therefore as the reactant is metabolised, concentrate drops and further metabolism slows
Reaction rate and drug concentration have a linear relationship
Second Order Kinetics
Rate of reaction is directly proportional to the square of the concentration of the reactant
Rate of reaction decreases faster than linearly as concentration goes down
Third Order Kinetics
Rate of reaction is proportional to the product of concentration of 3 of the reactants
Pharmacodynamics
What the drug does to the body
What receptors does it activate?
What other effects does it have?
Pharmacokinetics
What the body does to the drug
ADME
How does the drug get into the body? (Absorption)
Where does it go? (Distribution)
What does the body do to the drug? (Metabolism)
How does the body get rid of the drug? (Excretion)
Half life
Definition
The time it takes to remove half the current concentratiom of drug from the body
