intro to pharmacology Flashcards
what is pharmacology?
the study of substances that interact with living systems through chemical processes
define drug
any substance that interacts with a molecule or protein that plays a regulatory role in living systems
define endogenous drugs
drugs originating inside the body, including hormones
define poisons
drugs that almost exclusively have harmful effects
why are all drugs poisons?
because all drugs have adverse effects
what are toxins?
poisons of biological origin, usually synthesised by plants or animals
define receptor
a specific molecule (usually a protein) that interacts with a specific chemical, causing a change in the receptor that produces a regulated function
name the types of receptors
ion channels
g-protein coupled receptor
RTKs
intracellular hormone receptors (nuclear receptor)
what is the largest category of receptor?
GCPRs
what is an agonist
any drug that binds to a receptor and activates it
name the types of ion channels
ligand gated
voltage gated
2nd messenger regulated
how does an agonist work?
mimics the natural ligand of the receptor. when the agonist leaves the receptor is usually deactivated and the effect stop
give some examples of agonists that cause a covalent change in the receptor
aspirin - makes a covalent change in the receptor that keeps anti-platelet action on for the life of the platelet
what is a partial agonist?
an agonist that binds to a receptor at the active site but is unable to cause maximal response even if all the receptors are occupied
why are partial agonists useful?
its hard to give an overdose with them
why do partial agonists have a smaller effect than full agonists?
they bind with a lower affinity for the receptor so they dont bind as strongly
why does a partial agonist block the full agonist?
because they both bind to the same active site
what is an inverse agonist?
an agonist that produces a response below the baseline response. it has an opposite effect to an agonist
give an example of an inverse agonist and how it works
antihistamine - binds to a histamine receptor and stabilises it so it stops mast cells and basophils from releasing histamine granules and causing an immune response
what is an antagonist?
any drug that binds to the receptor and prevents activation of the receptor
define competitive antagonist
a drug that competes with the endogenous ligand for the the binding site. fits into active site and prevents activation of the receptor
define non-competitive antagonist
a drug that binds to the receptor at a point that isn’t the binding site
what is a chemical antagonist?
a chemical that binds directly to an agonist and prevents it from binding to a receptor
what is a physiological antagonist?
when 2 substances have exactly opposite actions via different pathways
what does ADME stand for?
absorption
delivery
metabolism
elimination
what is a strong acid?
an acid that dissociates completely into a negative ion and a proton
what is a weak acid?
an acid that only partially dissociates
which form of a drug is lipid soluble?
undissociated form
uncharged and protonated
which form a drug is water soluble?
dissociated form
what is the advantage of a drug being a weak acid/base?
it can switch between the dissociated and undissociated form so it can travel through different parts of the body
in acidic solution, what form is a weak acid drug going to be in and why?
in the uncharged and undissociated form because the H+ ions in solution push the equilibrium to the left
in alkali solution, what form is a weak acid drug going to be in and why?
charged and dissociated form because fewer H+ ions so equilibrium moves to the right
when does pKa = pH?
when there is complete balance between the uncharged and charged form of the drug
what is the range of pH of the body?
7.35-7.45
what form is a weak acid drug generally going to be in the body and why?
charged and dissociated form because body pH is slightly alkaline so equilibrium shifts to the right to make more H+
where is most of the protonated form of a drug found?
in the stomach
what are drugs filtered by?
the glomerulus of the kidney
what form of a drug will be reabsorbed back into the blood in a kidney?
a protonated, undissociated drug
in what pH blood is a weak acid drug excreted fastest and why?
alkaline urine because more will be in the unprotonated form
in what form will a drug be excreted?
dissociated form
in what pH blood is a weak alkali drug excreted fastest?
acidic
what is specificity?
which organ(s) a drug works on
what is selectivity?
what receptor a drug binds to to produce an effect?
define affinity
how tightly the drug binds to the receptor
what bonds can a drug bind to a receptor with?
covalent ionic electrostatic lipophilic van der waals
define pharmacokinetics
actions of the body on the drug
define pharmacodynamics
actions of the drug on the body
why is a logarithmic scale used?
easier to get dose reading on a logarithmic scale
what is the maximal response?
the point where there is no further increase in response
what does EC mean?
concentration
what does ED mean?
dose
what does EC50 mean?
the drug concentration at half the maximal response
how can you tell a drug is a competitive antagonist from a graph of response against concentration?
need to add more of the drug to get a response. with enough of the agonist added, a maximal response can be achieved
how can you tell a drug is a non-competitive antagonist from a graph of response against concentration?
maximal effect is reduced
no matter how much agonist you bind, it cannot activate receptor at the same level bc the receptors its binded to cannot be used anymore.
do all receptors have to be occupied to produce a response?
no
how do spare receptors impact a tissue’s response to a ligand?
increase sensitivity and speed of the response
define efficacy
the maximal effect that a drug can produce regardless of dose
define potency
the amount of drug that is needed to produce a given effect
what determines potency?
affinity of a drug for a receptor and the number of receptors available
which axis does the curve move in to show potency
horizontally
which axis does the curve move to show efficacy?
vertical
if a drug is more potent, which direction does the curve move in?
the right
if a drug has a lower efficacy, which way does the curve move in?
down
define intrinsic activity
the ability of a ligand to bind to receptors and activate them
