Pharmacodynamics, principles of drug action Flashcards
(19 cards)
What is receptor (R) theory?
2 step process:
1. Drug binding (affinity)
2. signal activation (efficacy) DR complex must signal to an effector to have an effect
Drug (D) + Receptor (R) <–[Affinity]–> DR complex –[Efficacy]–> Effector —> Response
What is the law of mass action?
calc Ke and KD
the rate of chemical reaction is proportional to the product of the reactants.
Ke = KF/KR
KD, (dissociation constant) = KR/KF
What is a drug.
A chemical applied to a physiological system that affects its function by increasing/decreasing physiological response.
What are different types of antagonism?
**Pharmacological level: **
- 2 drugs competing for the same receptor: surmountable or insurmountable (allosteric or active site)
Tissue/organism level
- 2 drugs with opposing effects mediated by different mechanisms
Chemical level
- 2 unbound drugs combining in solution/binding to drug target in solution
True or False
KD is a measure of affinity
True
Factors affecting affinity
- concentration
- stability of complex formation
- molecular size
- shape
- electrical charge
True or Fasle
EC50 is a measure of potency.
True
Potency is related to the dose required to produce a give degree of response.
EC50 is the concentration of drug required to produce therapeutic effects in 50% of the population.
True of False
Emax is a measure of efficacy.
True
They are proportional
What is efficacy?
- The ability of bound ligand to activate the receptor.
- Agonists elicit a direct response
- Antagonists has no efficacy at the receptor thus produce no direct response (no signalling mechanism)
Full agonists have an efficacy of 1
Partial agonists 0<efficacy<1
Antagonists efficacy = 0
Inverse agonists efficacy < 0
(Intrinsic) pharmacological efficacy vs clinical efficacy of antagonists.
- Phamacological efficacy = 0 (no diresct response)
- Clincal efficacy is not 0 (because it is defined by the drug’s ability to achieve therapeutic outcomes)
What is a graded drug response.
Response varies in magnitude in dose-dependent manner.
Normal dose-response curve
What is quantal drug response.
Quantification of the # of subjects responding to the drug that varies in a dose-dependent manner.
Different drug concentration shows different # of indivs responding
In the receptor theory, what does receptor refer to?
- CSM receptors
- ion channels
- enzymes
- transporters
- nucleic acids
How do receptors affect selectivity of drug action?
Receptors are very specific, affecting:
1. Drug size
2. DR interactions (H2ID)
3. Drug shapes
Its effects and how does it work
Mannitol
Mannitol is an osmotic diuretic.
- it is a large polar molecule
- creates osmotic gradient in tubular lumen, favoring water movement into tubular lumen for excretion
Its effects and how does it work
Antacids: aluminium/magnesium hydroxide
neutralises stomach acids because they are alkaline
Its effects and how does it work
Activated charcoal
- adsorption and detox binding to toxins
- non-specific binding to non-polar compounds with high molecular weight
Its effects and how does it work
Chelating agents
-used for detox
- have multiple electron-donating groups to form dative bonds with metal ions (mercury), and forms a chemically stable shelate-complex
Define PD
Pharmacodynamics refers to the relationship between drug concentration at the site of action and the resulting effect, including the time course and intensity of therapeutic and adverse effects.
