Drug action Flashcards
What is a drug
“external substance that acts on living tissue to produce a measurable change in the function of that tissue”
What is the difference between effects and side effects
effects - effects you want
side effects - effects you don’t want
what do local anaestheics do
prevent pain
what do antimicrobials do
treat and prevent infections
what do anxiolytics do
reduce anxiety
what do analgesics do
reduce postoperative pain
What can drugs do?
- simulate normal body communications
- interrupt normal body communications
- act on non-host organisms to aid body defences
where do hormone messages affect
all tissues
where do neural messages affect
specific tissues
name 4 types of hormones
thyroid hormones
insulin
cortisol
sex hormones
what do thyroid hormones do
balance body’s metabolism
too much thyroid hormone?
hyperthyroidism
too little thyroid hormone?
hypothyroidism
effects of inbalance of thyroid hormone?
cold intolerant
slow mentation
hair loss
slow pulse and low bp
what does the thyroxine tablet do
replaces missing T3 and T4
where does the thyroxine table act on
directly on tissues - no direct effect on thyroid gland
What is the nerve control of the heart rate
Sympathetic - adrenergic stimulation
Speeds up the heart via Beta-receptors
Parasympathetic - cholinergic stimulation
Slows the heart via cholinergic receptors
What are the ‘autonomic’ drugs and what do they do
epinephrine - beta agonist
atenolol - beta blocker
pilocarpine - cholinergic agonist
atropine - cholinergic blocker
how do drugs interact with tissues
receptors
enzymes
ion channels
why are receptors by themselves not enough to cause a change by a drug
because they are coupled to ion channels/ G proteins/ enzymes/ gene transcription ?
What are the two components to drug-receptor interactions
drug-receptor interaction (affinity and occupancy)
drug reduced response (efficacy)
What does affinity mean?
how keen drug and receptor are to be together
What does occupancy mean?
time they are together
What does efficacy mean?
the effect output of affinity and occupancy. E.g. high affinity and high occupancy gives high efficacy
what is the law of mass action?
the principle that the rate of a chemical reaction is proportional to the concentrations of the reacting substances
What is an agonist
fits to receptor and causes the effect you want the drug to cause
what is an antagonist
fits to the receptor but doesn’t cause an effect - blocks receptor
whats a partial agonist
binds and causes a bit of change
what effects can you get with partial agonists
more difficult to produce the drug/receptor effect than with an agonist. Increase partial agonist conc will improve efficacy for some but not for others
What are the different types of antagonist
competitive and non-competitive
what are the different types of responses you can get with antagonists
reversible
Antagonist effect reduced by increasing the
concentration of the agonist
Example: atenolol (β1 blocker)
irreversibe
Binds and reduces available receptors for the agonist
Example: phenoxybenzamine (α1 blocker)
why can partial agonists be particularly helpful
by changing the conc you can change the response
Enzymes
What is substrate antagonism
?
Enzymes
What is reversible enzyme modification
(?)The other method of control is called reversible covalent modification. This involves the addition or removal of some type of group, most commonly the phosphoryl group, onto or from the enzyme. The addition of phosphoryl groups involves the use of ATP (energy source) and requires a protein called protein kinase
Enzymes
What is irreversible modification
(?) Probably do to with the protein being changed permanently
2 examples of drugs where enzymes have an effect
aspirin and simvastatin
How do ions affect D/R interactions?
2 examples?
electrical activity
ion influx
LAs and anti-diabetic drugs
can both agonists and antagonists be competitiative?
yes - occupancy and affinity affect efficacy
how do drugs act
through:
receptors on cells
influencing enzyme action
disruption of ion conduction channels
