mechanisms of drug action Flashcards
types of drug antagonism
receptor blockade, physiological antagonist, chemical antagonism and pharmacokinetic antagonism
explain receptor blockade
competitive or irreversible
explain physiological antagonism with example
drugs act on different receptors in the same tissue to have opposite effects
NA and histamine constrict vs dilate vascular tissue
explain chemical antagonism with example
one drug mixes with another in solution to negate it
dimercaprol is a chelator to form heavy metal complexes
explain pharmacokinetic antagonism, ways in which its done and example
a drug that reduces conc of active drug at site of interaction
done by less absorption, more metabolism or more excretion
barbiturates
what is drug tolerance
decrease in responsivenesss with repeated administration
causes of drug tolerance with examples
pharmacokinetic factors (increased metabolism eg barbiturates and alcohol)
loss of receptors (cells downregulate receptors by endocytosis eg B adrenoreceptors)
change in receptors (become desensitised by undergoeing conformational change eg nAChR
exhaustion of mediator stores eg amphetamine causes NA release by inhibiting transporter to give euphoria
physiological adaptation (homeostatic response eg to antihypertensive drugs- can also be good as gives tolerance to drug site effects)
types of receptor families: speed and examples
type 1 ion channel linked (fast in ms eg ACH), type 2 G protein coupled (slow in secs eg B1 adreno), type 3 (kinase-linked eg insulin/growth: mins) and type 4 (intracellular steroid receptors eg steroids and thyroid hormones- regulate DNA) hrs
explain coupling of receptor families
type 1 and 3 are direct, type 2 is G protein, type 4 is via DNA
explain effectors of receptor families
type 1 channel, type 2 enzyme/channel, type 3 enzyme, type 4 gene transcription
