Pharmacodynamics Flashcards
What is molarity?
Molar concentration, also called molarity, amount concentration or substance concentration, is a measure of the concentration of a solute in a solution, or of any chemical species, in terms of amount of substance in a given volume: Molarity (M) = g/L / MWt
What is a ligand?
molecules that binds specifically to a receptor. Have intrinsic efficacy (can active receptor) have efficacy (cause a measurable response)
Describe affinity
to bind a receptor a ligand must have affinity for receptor, measure of strength of binding – higher affinity = stronger binding, high affinity allows binding at low conc
What is efficacy/intrinsic activity?
ability of the ligand to cause a response – governed by intrinsic efficacy
What is the name given to something that binds and activates a receptor?
agonist
How is potency defined?
effective conc giving 50% maximal response, depends on affinity and intrinsic efficacy. Potency = affinity + intrinsic efficacy
Describe what a partial agonist is
all receptors occupied but insufficient intrinsic efficiency for maximal response = lower intrinsic activity as they have lower efficacy then full agonists. Allows more controlled response. Work in absence or low levels of ligand. E.g. buprenorphine – higher affinity = lower Kd, but lower efficacy (no full response) more morphine
What is intrinsic efficacy?
ability to change the receptors shape making it active
What binds but does not activate a receptor?
Antagonist = binds but doesn’t activate receptor = no conformation change = no interaction with effector. Drug blocks the binding of an endogenous agonist
What is functional antagonism?
act at a completely separate receptor, initiating effects that are functionally the opposite of the agonist
What is reversible competitive antagonism?
compete with agonists for binding – inhibition is surmountable
Commonest, greater [antagonist] = great inhibition, relies on dynamic equilibrium between ligand and receptors. Cause a parallel shift to the right of the agonist conc-response curve
Outline irreversible competitive antagonism
occurs when the antagonist dissociates slowly or not at all – binds with such high affinity or change shape of receptor that another agonist will never bind = non-surmountable
What is non-competitive antagonism?
binds orthosteric site (not active site)
How can we measure drug-receptor interaction?
binding a radioactively labelled ligand, measure amount present
What is Bmax and Kd?
Bmax = max binding capacity – information about receptor number.
Kd = 50% receptor occupancy = measure of affinity, LOWER VALUE = HIGHER AFFINITY
