intro Flashcards
define a drug
a substance that alters chemical reactions in the body
it has two properties: exerts a selective physiological effect (something we can measure)
a compound with a defined medical structure (not a mix)
what is the EFFECT of drugs
interaction with a molecular target on cells, most often a protein
4 major classes of protein targets
enzymes
transporters
ion channels
receptors
receptors in detail
-although there is over 2000 receptors in the human body they have some common characteristics which is useful in pharmacology
common characteristics:
-selective binding sites for hormones or transmitters
-Receptors function like switches, turning on (active state) and sending a signal inside the cell when the right key (ligand) binds to them, while remaining off (inactive state) and sending no signal in the absence of the key
-signals are amplified 1000s of signalling molecules eg.
ions flowing through a channel triggering further downstream signaling events
Second messengers/enzymes amplify the signal within the cell and can affect many cellular processes.
mRNA molecules for new proteins: The signaling cascade activated by the receptor can ultimately lead to the expression of genes, resulting in the production of new mRNA molecules. These mRNA molecules are then translated into proteins that mediate cellular responses.
the two types of receptor drugs
- one that mimics the messenger so
AGONISTS reproduce the effects of endogenous messenger
-one that opposes the messenger
ANTAGONISTS block the effects of endogenous messenger
ENZYMES
TRANSPORTERS
ION CHANNELS
how does drug effect
Predominantly one type of drug – inhibitors
the extent to which the drug binds depends on the…
local concentration at the target sight
two processes that influence the dose of drug required
PHARMACODYNAMICS: Effect of drug on target cell / tissue
PHARMACOKINETICS
How body controls drug
concentration at site of action
Pharmacokinetic parameter
Pharmacokinetic parameters describe the movement of a drug through the body over time.
can be abbreviated to ADME
Absorption
Distribution
Metabolism
Excretion
Toxicity
what does a drug being selective mean
If drug is selective – it’s targeting the “right” cell / tissue for a biological response.
Another idea of drug selectivity is that - it interacts with the binding site of the “correct” molecular target.
on-target - means effect produced by intended interaction with the correct molecular target
off-target – means effects produced by unintended interaction with a different molecular target
example Treating bronchoconstriction in asthma
Mimic airway effects of adrenaline
Avoid other effects (e.g. on heart)
adrenoceptor agonist, which means it activates adrenoceptors found in the smooth muscles of the lungs (doesnt activate receptors in the heart )
Pharmacokinetics also important – Targeted airway delivery by inhaler – avoids systemic exposure.
what does interaction between drug and protein depend on
-depends on how well the drug molecule fits into the protienactive site, the better the fit the higher the affinity the drug has for its target producing more effects at a lower concentration
side effects
All drugs interact with additional binding sites at higher concentration, which can lead to unwanted side effects
All drugs therefore have both clinical benefits and risks
-requires evidence-based judgements e.g. for market approval
