Test 3 - Pharmacology - I and II Flashcards
What is pharmacokinetics?
The actions of the BODY on drugs
What is pharmacodynamics?
The actions of DRUGS on the BODY
*Act on receptors
What is an agonist?
Drug or natural ligand -Activates Rc (receptor) -can be selective or not -Examples —Neurotransmitter —Hormone —Drug that mimics a ligand
What is an antagonist?
Something that binds the receptor, but does not activate it
—Interferes with agonist
—Shifts dose-response to the right
—Most drugs are these, except antibiotics
*If enough agonist is present, then the agonist will start to bind and activate the receptor
What is a competitive inhibitor?
An antagonist that binds the active site on a receptor and competes with the agonist at that site
What is an allosteric activator?
Binds the receptor at a site separate from the agonist site
—Potentiates effects
What is an allosteric inhibitor?
Binds the receptor at a site separate from agonist site
—Noncompetitive
—Actions often reversible
—This changes the active site and decreases the Rc’s affinity for the agonist
Ra = ?
Ri = ?
In the absence of drugs, the two isoforms are in Eq and what is favored?
Active receptor
Inactive receptor
**Ri
What is a full agonist?
High affinity for the Ra conformation, and Ra-D = much larger effect
What do partial agonists do?
Produce lower response than full agonists
—Don’t get to same plateau as full agonists do
—Doesn’t stabilize Ra-D as well as full agonists
What is an inverse agonist?
Not the same as an antagonist
—Greater affinity for Ri
—Acts like a sponge, less Ra available, so less activity occurs
What is a conventional agonist?
Equal affinity for the Ra and Ri, no change in constitutive activity
What is Kd?
Infinity constant
—Conc of drug to get 50% of receptors bound
What is EC50?
Effective conc for 50% of drug’s max effect
What is IC50?
Inhibitory conc
—Antagonist conc
On graphs of inhibition, compare and contrast competitive inhibition with non competitive inhibition.
Comp inhib
—EC50 shift to right (higher dose of agonist necessary for desired effect)
Noncomp inhib
—Plateau of desired effect is greatly diminished, but EC50 does not move
T/F - When mixed, a full agonist can be displaced by a partial agonist, and the total response is decreased.
TRUE
Name and describe the 3 types of drug receptor interactions.
Additive (Summative)
—1+1=2
—Net effect is the sum
—Example: ibuprofen + acetaminophen
Synergistic (Supra-additive)
—1+1=5
—Net effect is greater than the sum
—Example: alcohol + sleeping pill
Antagonistic (Infra-additive)
—1+1=0.5
—Net effect is less than the sum
—Example: Antidotes
What is a chemical antagonist?
Does NOT involve a receptor
—(+)protein counteracting effects of a drug that is (-) charged
What is a physiological antagonist?
Involves endogenous regulatory pathways mediated by different receptors
Define efficacy.
Greatest effect that can be had
—Low efficacy - 12%
—High efficacy - 100%
Define potency.
Relative concentrations of 2 or more drugs that produced the same effect.
Potency = position on graph. More left on the graph, more potent.
—Higher potency drug will require low amount of drug to get to EC50
What is desired, a less steep or more steep drug curve?
LESS steep
The curve most left on the graph is what?
Most potent
The highest achieving drug curve on the graph is what?
Most efficacious
*Look in pics for the graph that will probably be on the test
What 2 factors govern drug action?
Affinity
—Measure of the tightness that a drug binds to the receptor
Intrinsic activity
—Ability of a drug, once bound, to generate an effect
T/F - A drug with a high therapeutic index is desired.
TRUE
TI = TD50/ED50
TD50 = Toxic dose in 50% of population
ED50 = Efficacious dose in 50% of population
*So a high therapeutic index is desired because if 100 pills of drug X are toxic to 50% of population, and the efficacious dose for 50% of the population is 1 pill, then that drug is good. However, if 2 pills of drug X are toxic to 50% of population, and the efficacious dose for 50% of population is 1 pill, then that is not desired because the room for error is too much
What is the loading dose?
An initial large amount of drug given to increase concentration of that drug in the blood.
*Next would be keeping the drug in a safe range of conc in the blood to have its effects
Safe drugs have a ________ margin of safety.
WIDE
*True definition is the amount of drug lethal to 1% of animals divided by amount of drug that causes beneficial effect in 99% of animals
What does parenteral mean?
Not by way of intestine or GI tract
What are the most common modes of parenteral drug administration? (3)
IV - Most rapid, easy to titrate and can enter direct circulation immediately
Intramuscular - Rapid, sometimes painful
Subcutaneous (SubQ) - Not rapid, smaller volumes req’d compared to intramuscular, sometimes painful