F1 What is a drug? Flashcards
what is a drug?
a substance that alters chemical reactions in the body to give a physiological result
what 2 properties do drugs have?
- exerts a physiological effect
- a compound with a defined chemical structure
what are the 4 major classes of protein targets?
- enzymes
- transporters
- ion channels
- receptors
most drugs work at protein drug targets of various classes. give a drug that is an exception to this
Rennie
- contains bicarbonates that neutralise excess stomach acid
what are receptors?
proteins in the body which respond to an endogenous messenger by initiating a signal
give examples of endogenous messengers
hormones
neurotransmitters
what are common characteristics of receptors?
- selective binding site for native hormone/transmitter
- act as molecular switches (have inactive and active states)
- signal is amplified
what are the 2 types of receptor drug?
agonists and antagonists
what do agonists do generally?
mimic/reproduce the effects of endogenous messengers
what do antagonists do generally?
block the effects of endogenous messengers
what type of drug targets enzymes, transporters and ion channels?
predominantly inhibitors
what types of drug target receptors?
- at least 2 types of drug with opposing actions at the same target
- agonists and antagonists
what factor determines the extent to which a drug binds to its target?
its local concentration
what are the 2 branches of pharmacology?
- pharmacokinetics
- pharmacodynamics
what are pharmacokinetics?
- how the body controls drug concentration at the site of action
what are pharmacodynamics?
- the effect of the drug on the target cell/tissue
what are is ADMETox and what does it stand for?
- Absorption, Distribution, Metabolism, Excretion, Toxicity
- the parameters for pharmacokinetics
what do we mean by selectivity?
- drug targets the correct cell/tissue for a biological response
- drug interacts with the binding site of the correct molecular target
what are on-target and off-target effects?
- on-target: an effect produced by intended interaction with the correct molecular target
- off-target: an effect produced by unintended interaction with a different molecular target
what is the related neurotransmitter to adrenaline?
noradrenaline
what are the receptors for adrenaline?
adrenoceptors
what does adrenaline do when it binds to adrenoceptors in the airway?
- opens airways
- more gas into lungs for gas exchange
- enhances gas exchange (more oxygen and carbon dioxide transferred)
what does adrenaline do when it binds to adrenoceptors in the heart?
- increased heart rate
- increased circulation of blood to muscles
what must be considered when treating asthma in terms of the effect of adrenaline?
- mimic airway effects of adrenaline
- avoid other effects eg. on the heart
why do the effects of adrenaline on the heart need to be avoided when treating asthma?
may cause palpitations
how does salbutamol demonstrate selectivity generally?
- selective adrenoceptor agonist
- mimics the effect of adrenaline on airways but not the heart
- activates adrenoceptors in the lungs better than the heart
how is the administration of salbutamol in an inhaler important for pharmacokinetics?
- targets the delivery to the airways and limits the systemic exposure of salbutamol
- this means it is less likely to reach other adrenoceptors (eg. in the heart) and cause side effects
what does the strength of interaction between a drug and its protein target depend on?
- depends on the drug ‘fitting’ into the 3D protein binding site
- the better the ‘fit’ the higher affinity the drug has for its target
what does a higher affinity between a drug and its target mean?
the drug will produce its effects at a lower concentration
is drug selectivity concentration-dependent?
- yes
- all drugs will interact with additional binding sites at higher concentrations which can lead to unwanted side effects
