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Pharmacology
37 cards·by samiaa.e
What is a drug
A substance that affects the body and elicits a change in physiology
How do drugs work?
Binding to targets and inducing a response
What are agonists
Agents that elicit a positive response
What are antangonists
Agents that act as inhibitors, preventing activity of endogenous
hormones/neurotransmitters or inhibiting enzymes
What are partial agonists
Agents that elicit a positive response but not to the complete extent possible, often used
clinically as inhibitors
What are inverse agonists
Agents that elicit the opposite response to the endogenous ligands
Name some different types of drugs
Very small -lithium ions, very large - therapeutic antibodies, lipits, peptides, proteins,
nucleic acids, carbohydrates
What is the law of mass action
The rate of a chemical reaction is directly proportional to the product of the activities or
concentrations of the reactions
What do a drug and receptor form
Drug-receptor complex
What is the dissociation constant
The concentration of a drug which, at equilibrium occupies 50% of the available receptors
What does Kd measure
The likelihood the drug receptor complex will dissociate
What does a high Kd show
Lower binding
What does the affinity constant KA show
The propensity of the drug to bind to the receptor
What does a high KA show
Greater binding
What is efficacy
The maximum effect achievable, Emax
What is potency
The dose of drug necessary to have an effect, lower does requed=greater potency
What is EC50
half maximal response (measure of potency)
How does increasing potency affect EC50
Decreases it
What is the receptor occupancy theory
A maximal response can be achieved with less than maximal receptor occupancy - spare
receptors
What is the therapeutic window
The gap between therapeutic and toxic effects
What is the therapeutic index
Conc of toxic drug/conc of therapeutic drug
What do agonists have
Affinity for the receptor and efficacy
What do partial agonists have
Affinity for the receptor but lower efficacy than full agonists
What do antagonists have
Affinity for receptor but no efficacy
Different types of antagonisms
Chemical, receptor, non-competitive, pharmacokinetic, physiology
Three major types of receptor antagonism
Reversible, competitive ; irreversible, competitive ; allosteric
What is reversible, competitive antagonism
High affinity, no efficacy ; Emax not depressed ; parallel shift to the right in the dose
response curve
What is irreversible, competitive antagonism
Bind covalently to receptor;decrease in total number of available receptors & max
response;non-parallel shift Emax; need new receptors
What is allosteric antagonism
Binds to a separate site on the receptor from the ligand;alters conformation of the
receptorto limit agonist binding or to prevent a respons
What features does allosteric antagonism have
No change in EC50 ; reduced Emax ; can be reversible or irreversible depending on type of
binding to allosteric sit
How can different antagonists be compared
Repeated dose-response curves are generated +_ different doses of antagonists, changes in
EC50 are recorded and dose-ratio made
What is dose-ratio
EC50 with antagonist/EC50 of agonist alone
What is pA2
pA2 is the neg log of the concentration of antagonist which reduces the response of a tissue to a
double dose of agonist to a single dose
What is pA2 affected by
pH and temperature
What is pA2 not affected by
Agonist used or tissue expressing a receptor
What is pharamcokinetic antagonist
Agents that enhance drug metabolism or limit drug access through sequestration
What is physiological antagonism
Two drugs can have opposing actions through different receptors on the same tissue,
cancelling out each others effect