W3- Lecture 14.1- Pharmacodynamics Flashcards
What three just properties does drug efficacy and safety depend on ?
Selectivity/ Specificity
Potency
Efficacy
What is the difference from selectivity and specificity ?
Selectivity- the ability of a drug to produce an effect and relates to structure that determines receptor specificity
Receptor specificity- determined by precise interactions between drug and receptor protein (aka affinity )
What makes a drug promiscuous?
A receptor that can be activated by multiple drugs
Or a drug that can couple will multiple partners
Describe the action of propranolol – a β-adrenoceptor blocker (antagonist) in lowering blood pressure
+ unwanted effects
propranolol – a β-adrenoceptor blocker binds to β1 and β2 adrenoceptors
Blockade of the β1 receptors in the heart decrease Heart rate hence lowering blood pressure
Unwanted effects blockade of the β2 adrenoceptors inhibits bronchial smooth muscle and can cause bronchial spasms in people with asthma and COPD
Define drug potency
The dosage of a drug needed to induce an effect
Graph y axis % response
X axis log [Dose ]
Two identical curves one more translocated to the right which is more potent ?
The one to the left
Lower the dose to produce the same effect
Why do we determine potency at the 50% max response ?
Easier the measure and compare for a log graph
How would we measure agonist concentration + response
simple systems
Measure tissue response e.g force off contraction
Compared to dosage of a drug until an maximal response (Emax)
How would your expect a % Response graph look plotted against concentration
% vs log conc
Hyperbola- increase then plateaus
Sigmoid- s shape slow increase fast then slow again
How would you determine potency and efficacy in a % action vs conc graph
Potency - 50% maximal response
Efficacy - maximal response (height)
Define efficacy
The ability of a drug to induce an effect
What is a full and partial agonist
Full agonist – at specific doses can induce a full physiological response, i.e. a full and maximal muscle contraction.
Partial agonist – describes a drug that cannot induce a full physiological response regardless of the dose.
Why might we use a partial agonist instead of a full agonist
Therapeutic effect without risk of overdose
E.g methadone vs heroin
What is an agonist ?
Substance that binds to a receptor to produce a response
What is the constant for the agonist binding and dissociating with the receptor ?
Binding - k+1
Dissociating k-1
