PHARMACOLOGY Flashcards
what are the 4 drug targets ?
receptors, ion channels, enzymes, transport proteins
what is a drug
a chemical that affects physiological function in a specific way
what is affinity
the tendency of a ligand to bind to its receptor
what is an agonist
A ligand that binds to a receptor results in a biological response- evokes activation
what is an antagonist
A drug that reduces the action of another drug ( usually the agonist)
what is a partial agonist
An agonist that cannot produce as large an effect as can another agonist even with 100% receptor occupancy acting through the same receptors
what is efficacy
tendency for the agonist to activate the receptor to evoke a response
what is drug potency
conc . / amt of drug needed to produce a response
eg: EC50
explains drug activity, depends on receptor and tissue
what is dose
a specified quantity of drug administered
what causes adverse drug reactions?
High doses (leading to higher blood-plasma concentrations) can lead to the drug binding to ‘off targets’ and/or the appearance of adverse drug reactions.
This is because no drug is completely specific to a particular recpetor
disassociation equilibrium constan KA is
concentration of ligand required to occupy 50% of the receptors
Lower the Ka ___ the affinity for the receptor
Greater
when [A] = KA, pAR = ?
0.5
what is the Hill-Langmuir equation?
pAR = [A]/ KA + [A]
relationship between ligand concentration and receptor occupancy
what is chemical antagonism?
Chemical antagonism – the antagonist combines in solution directly with the chemical being antagonised
(e.g., chelating agents, used to treat lead poisoning, bind to heavy metals and form a less toxic chelate).
what is pharmacokinetic antagonism?
Pharmacokinetic antagonism – one drug reduces the effect of another drug by accelerating its metabolism or elimination
e.g., phenobarbitone increases hepatic metabolism of the anticoagulant drug warfarin)
what is physiological antagonism?
Physiological antagonism – Two agonists that produce opposing physiological actions and cancel each other out.
Each drug acts through its own receptors
(e.g., adrenaline relaxes bronchial smooth muscle reducing the bronchoconstriction of histamine)
what does Pindolol do?
drug
it is a partial agonist at beta1 and beta2 adrenoreceptors