Flashcards in Pharmacology Definitions Deck (38):
how the body handles and process drugs
how drugs act on the body via drug receptor interactions
what is a drug
its a substance that changes physiology through its chemical actions
what is a toxicant
its a poison or poisonous agent that has almost exclusively harmful effects
what is a toxin?
its a toxicant of biological origin (eg endotoxin, venom, poison ivy toxin, ricin)
what is a dose?
is the difference between a drug and a poison, or a foodstuff and a poison
All drugs have 3 types of names. what are those subcategories?
chemical name, generic name, commercial/trade/brand names.
how do cells comminicate in the body?
they use intercellular signalling molecules, which interact with proteins and receptors in the plasma membrane to regulate biochemical pathways in the cytoplasm
what is the signal transduction pathway?
its the receptor, its cellular target and any intermediary molecules involved in a chemical message.
in order for drugs to interact with receptors, they need to possess adequate what?
size, charge and shape/atomic composition
what is the range of size of drug molecules?
lower limit ~100MW: minimyum size needed to impart specificity of action
upper limit ~1000MW: size limit allowing reasonable movement in the body to site of action
Very large drugs must be administered directly to site
what makes a drug receptor selective?
its when the chemical bind/force is weak between the drug and the receptor. they require more precise fits if the interaction were to occur.
how could a drug interact with the receptors that dont have optimal fits?
if the D-R bond is strong enough.
what are the 3 kinds of bonds that exist ?
1. covalent (rare/strong/irreversible)
2. Electrostatic/hydrogen/van der waals (weaker/many D-R interactions)
3. hydrophobic (very weak/most important with lipid interactions and highly lipid-soluble drugs/many D-R interactions)
what is an enantiomer?
its a chiral centers, drugs that act this way may be more potent because the reflect better fits with receptors.
in what two ways do drugs modify signal transduction after binding to receptors?
1. they can initiate or enhance
2. they can diminish or terminate (block)
how can a drug be effective immediately vs. delayed?
depending on the signal transduction pathway being modulated. the effect is genereally proportional to the percentage of receptors occupied by the drugs.
what is a second messenger?
its a cytoplasmic molecule that translates D-R interactions into a change in cellular activity. They are acted on by effortor molecules
what is a well-established second messenger?
they entail reversible phosphorylation of key target (enzyme). its allows for amplification of signal, and allows for flexible regulation of signalling
most drugs act on receptors that have what kind of lingand, (provide examples)
neurotransmitters and hormones
why are drugs given therapeutically?
1. to stimulate receptors in hypofunctional states
2. block receptors in hyperfunctional states.
what is an agonist?
it activates receptors and initiates cellular responses
what is a partial agonist?
an agonist that is not able to fully activate the receptor
what is an antagonist?
binds but does not activate the receptor (simply prevents agonists from stimulating the receptor)
what is an inverse agonist?
it reduces constitutive activity of receptor.
waht is the dose-response curve?
DRC is a depiction of the observed drug effect with (% maximal response) as a function of drug concentration.
its the concentration of a drug required to produce a given effect; measure of a drug's affinity for and activity at the receptor. Normally defined by the half-maximal effective concentration (EC50)
how do you measure realtive potency?
comparison of EC50 values between drugs acting at the same receptor
is the most potent drug the most efficacious?
when would low potency be a concern?
if the volume of the required does is too large to be convenient
what is efficacy?
the magnitude of the cellular response produced when all receptors of a given type are occupied by the ligand
(its defined by the maximal response (Emax) of the drug.
how do you measure the relative efficacy?
comparing the maximal responses of drugs acting upon the same receptors.
what is a non-competitive antagonism?
antagonist that binds irreversibly to receptor or only very slowly dissorciates. higher agonist concentrations cannot overcome the effects of a fixed dose of antagonist.
whatr is a competitive antagonism?
antagonist has affinity for receptor by no efficaty, completes with agolnist at site. Higher agonist concentration can overcome the effects of a fixed dose of antagonist
antagonist produces parallel rightward shift in dose-responses curve.
What is tolerance?
its the gradual decrease in responsiveness to chronic drug administration. (desensitization/down-regulation)
what are some possible mechanisms for development tolerance?
1. temporary inaccessibility of receptors (phosphorylation)
2. sequestration of receptors in cell (internalization)
3. Reduced synthesis of new receptors
what is tachyphylaxis
refers to rapid (acute) form of tolerance