Pharmacology Flashcards
(23 cards)
Pros and cons of IV drug administration.
Pros
Rapid immediate onset
Permits titration
Cons
Infection
Pain
Risk of adverse effects
Pros and cons of IM drug administration.
Pros
Rapid onset
Shorter duration
Cons
Neurovascular damage
Pain
Infection
Pros and cons of subcut drug administration.
Pros
Prolonged effect
Constant slow absorption
Cons
Pain
Infection
Delayed absorption in shock
Pros and cons of enteral (oral/rectal) drug administration.
Pros
Convenient
Safe
Cheap
Cons
Absorption influenced by stomach contents
Gastric acid interferes with absorption
Uncooperative patients may not take
Define bioavailability. What symbol expresses bioavailability?
Fraction of the administered drug which reaches systemic circulation.
Expressed as letter F
F=1 for IV drugs
Describe factors affecting bioavailability
Molecular weight
Gastric pH
Grapefruit juice may increase bioavailability
Define volume of distribution.
The apparent volume into which a known amount of drug must be dispersed to give the measured plasma volume
What factors does the volume of distribution depend on?
Plasma protein and tissue binding
Molecular weight
Lipid solubility
What is the volume of distribution used to determine?
Loading dose amount
Elimination half life, dosage interval
Define clearance
Theoretical volume of plasma (blood etc) cleared of drug per unit time (mlmin-1)
What is the half-life of a drug?
Time taken for serum plasma concentration to decrease by half
What determines half-life?
Clearance and volume of distribution
VofD/clearance
How many half lives does it usually take to clear a drug?
4-5
What is the maintenance dose?
When rate in=rate out
What is steady state?
The amount of drug administered is equal to the amount of drug eliminated within one dosing interval.
How are half life and steady state related?
Drugs with a short half life reach steady state rapidly
Drugs with a long half life can take days to reach steady state.
Name the 4 common signal transduction methods of action with regards to drugs.
Enzyme linked
G protein linked
Ion channel
Nuclear
Define affinity.
Measure of propensity of a drug to bind to the receptor.
Define potency.
Amount required to produce an effect of given intensity
Relative position of the dose-effect curve along the dose axis
Define efficacy
Ability of a bound drug to change the receptor in a way that has an effect.
Describe an agonist.
Drug which bind to a receptor and activated the receptor to produce a biological response
Has affinity and intrinsic action
Describe an antagonist.
A drug which blocks a biological response by binding to a receptor.
Has affinity but no intrinsic activity
Describe therapeutic index.
A comparison of the amount of a drug that causes a therapeutic effect to the amount that is toxic.
