Unit 1 - Basic Principles of Pharmacology Flashcards
(45 cards)
drug action VS drug effect
molecular action is invisible
pharmacologic effect shoes visible response
define selectivity
selectivity: property of drug to cause a specific effect
- few drugs produce a single effect
primary VS secondary effects
primary: desired
secondary: “side effects” that may or may not be desired
pharmokinetics VS pharmodynamics
kinetics: time course of drug absorption, actions, and elimination
dynamics: types of drug actions
what are the types of pharmodynamics?
physiochemical actions - simple chemical interactions
-ex: antacids, antiseptics not very specific
receptor interactions - interaction of drug with physiologic receptors (most drugs are macromolecules)
drug-receptor interactions
cause molecular events to occur in each cell
-enough of events cause change in cell function resulting in change in tissue function
information on drug receptors
- macromolecules, particularly proteins, on or in a cell, or free in plasma or extracellular fluid
- specific and present as part of normal biochemical and physiologic mech, and usually interact with endogenous compounds
- function as both ligand binder and effector
- each cell in a tissue contains a large population of receptors that are easily accessible to drugs
when is a maximal response achieved?
related to number of drug receptor interactions and physiologic capacity of tissue (healthy VS diseased)
what are 5 types of receptors and examples?
membrane-bound: neural synapse, ion channels
enzymes: intracellular or extracellular
structural macromolecules: microtubules
intracellular macromolecules: steroid receptors, RNA
cell membrane: change electrical potential, fluidity
receptor amplification and transduction
drug-receptor interactions last fractions of seconds and activate G protein activity that lasts for seconds
information on G proteins
GTP binding proteins regulate activity of distinct effector proteins in cell
- there can be multiple GPRO in a single cell
- act as switches that are turned on by receptor and turn themselves off in a few seconds
- several drugs can stimulate different receptors but ultimately influence same effector PRO through mediation of GPRO that is shared by different receptors so stimulus averaging/modulation is achieved
receptor theory
structure-activity relationships
- structure of drug determines how it will fit into the receptor
- better fit has better stimulation
- subtle changes in structure among a class of drugs can greatly influence drug’s effects
log dose response curve characteristics
- threshold
- slope
- maximal asymptote
threshold: beginning of the curve
- dose of agonist at which response starts
- may relate to affinity of agonist for receptor
slope: rate of rise of response on steep portion of a curve
- log of EC50 also relates to affinity
maximal asymptote: top of the curve, represents E max for that particular agonist
receptor occupancy
intensity of response is proportional to fraction of receptors occupied
- effect = Emax * [D] / KD + [D]
- where Kd = EC50
intrinsic activity
ability to stimulate receptor once bound
- relates to structure and influences efficacy and potency
- greater intrinsic activity = greater efficacy (brings to Emax)
spare receptors
not all receptors need to be occupied to achieve Emax
-less efficacious agonists need to occupy more receptors than highly efficacious agonists
secondary receptors
outside of target tissue(s), may mediate other effects (side effects)
receptor regulation
a cell can up or downregulate a population of receptors by changing the total number of receptors or their sensitivity
difference between binding site and effector portion
effector portion needs to be bound in order to exert effect, but if binding site not bound, then weaker agonist
-if only binding site bound, then it’s an antagonist
what are the two ways of quantifying agonism?
efficacy and potency
what is efficacy? what does it depend on?
ability of drug to activate effector portion of receptor once drug is bound to receptor
-depends on structure of the drug
what is potency? what does it depend on?
relates to amount of drug that is needed for an effect
-depends on biologic system (receptor density, efficacy of stimulus-response mechanisms of tissue) and interaction of drug with receptor (affinity and efficacy)
types of noncompetitive antagonism
I - changes effector, does not change binding of drug to ligand site OR alters effector site so even if ligand binds to the receptor, it cannot initiate effect
II - changes binding site for agonist by directly binding to it or by attaching to a different portion of receptor and altering agonist binding site
filtration
passive process that’s driven by hydrostatic pressure
- drugs dissolved in moving fluid is transported through pores in a membrane or channels betweenc ells
- drug molecule size will be limiting