ICPP Review Flashcards
Drug action/ligands are dependent on the
Concentration of drug molecules around receptors
What is a ligand
• A ligand is a substance that can interact with target protein- or receptor
• Ligands usually bind to a specific site on the signalling protein(s)
• Can be endogenous signalling molecules
What is an agonist
Substance that binds to a receptor and produces a measurable biological response
What is an antagonist
Ligands that have affinity for a receptor or target protein but do not produce a biological response
Blocks the effect of agonist
What is affinity
How tightly a molecule is bound to its receptor- strength or avidity
What is the measure to define affinity
Kd = dissociation constant
Conc of ligand at which 50% of all available receptors are bound
Lower Kd =
Greater affinity
Intrinsic efficacy is a term used to describe the ability of a ligand to
Generate the active form of the receptor R
What is ligand efficacy
Cause a measurable biological response
How do we define agonist potency
Conc of a drug that evokes 50% of its maximal response Emax = EC50
What is a partial agonist
Ligands that evoke responses that are lower than the mammal response of a full agonist (have a lower Emax)
Lower intrinsic activity
Compared to a full agonist, a partial agonist has
Lower intrinsic efficacy (full agonist generates confirmation of receptor which is really good at activating downstream signals, partial agonist is less good at this)
Which drug has the highest intrinsic activity in a graph
Which drug has highest potency and affinity in graph
Pharmacodynamic principles reflected in Kd and EC50
Signal amplification and spare receptors
Which pharmacodynamic principle explains a higher Kd than EC50
Spare receptors
3 types of drug antagonism
• Reversible competitive antagonism (the same binding site as the endogenous ligand, interaction is relatively weak)
• Irreversible competitive antagonism (the same binding site as the endogenous ligand, interaction is irreversible and reflects high affinity with very slow dissociation, maybe covalent binding)
• Non competitive antagonism (generally allosteric- can ever work post-receptor)
Which organs are most likely to be affected by the major adverse side effects of atenolol (beta blocker for hypertension)
brain, kidneys, GI tract
most severe side effects
efficacy definition
E Max = maximal response achievable from a drug within particular system or tissue in body
intrinsic efficacy definition
a measure of how effective a drug is in inducing the active conformation of the target protein
What is potency
the dose of drug required to produce a specific effect of given intensity (usually EC50)
greatest potency and highest affinity will have
lowest efficacy and Kd
what does a bioavailability of 0.2 tell you
not much of the oral medication is reaching the systemic circulation. Undergoes a large amount of first pass metabolism
what will be the Vd of a lipophilic drug that also binds to muscle proteins
high ask it can enter the fat and muscle compartments
