Pharmacodynamics Flashcards
How do drugs act?
By combination with specific receptors
By alteration of enzyme processes
Pharmacodynamics
How a drug reacts to the body
Where do drugs act?
Receptors DNA Ion channels Hormones Enzymes
Agonists
Bind to receptor
Activates it
Partial agonist
Bind to receptor
Can elicit same magnitude of response as full agonist
Antagonist
Only bind to receptor
Inhibit stimulation
Antidotes to agonists
What are the 2 types of antagonism?
Competitive
Non-competitive
What are the 4 properties of drug action?
Specificity (for a receptor)
Selectivity (how good drug is at subtype of rec rather than another)
Potency (refers to CONC that is required to produce effect)
Efficacy (max effect)
Emax
Max effect a drug can have (measure if efficacy)
EC50
Effect of drug, at half given conc (measure of potency)
When efficacy is at 50%
Efficacy
Max effect of drug
Potency
A comparative measure
Refers to different doses if 2 drugs needed to produce the same effect
40g furosemide & 2mg bumetamide produce the same effect. Which is most potent?
Bumetamide
What drug must you never give to an asthmatic?
B blockers!
Give an example of a coumarin antagonist and what it blocks
Warfarin
Blocks epoxide reductase
What’s the antidote to warfarin?
Vitamin K
Competes with warfarin, so clotting factors can then be produced
Tolerance
Loss of response to a drug
Eg morphine - have to keep inc dose to get same benefits (get side effects, eg constipation)
Tachyphylaxis
Rapid loss of response
Desensitisation
Loss of response
Associated with receptors
Resistance
Loss of response
To chemotherepeutic agents
How may tolerance occur?
⬇️ no.of rec
⬇️ in response prod by rec
⬇️ in conc of drug @ rec
What is pharmacokinetic tolerance?
⬇️ in conc of drug @ rec
Drug speeds up its own metabolism
Do elderly patients require more or less warfarin than a younger patient to produce the same effect?
Less warfarin
What 5 factors influence QOL?
Mobility Self care Anxiety/depression Pain/discomfort ?
In what conditions is warfarin sensitivity increased?
Liver disease
Heart failure
Elderly
(If overdose= bleed)
Sources of vitamin K
Brussels sprouts Broccoli Spinach Cauliflower (Don't eat loads of these/ take vitamins if you are on warfarin)
What drugs have withdrawal effects?
Corticosteroids
B blockers
Antidepressants
Anticonvulsants
