Flashcards in Pharmacodynamics Deck (12)
1
Define 'affinity'
Mathetmatically represented as 1/Kd (dissociation constant). If the receptors have a high affinity for the ligand, the Kd will be low (takes a low concentration of ligand to bind to half of the receptors)
2
Define 'selectivity'
a drug’s ability to preferentially bind to certain receptors
3
Define 'specificity'
The number of different mechanisms involved; a high specificity involves binding to a small subset of receptors and not eliciting a large host of reactions
4
Define 'inverse agonist'
An agent which binds to the same receptor as an agonist, but induces a pharmacological response which opposes the agonist
5
Give an example of a drug which is a positive allosteric modifier
Benzodiazepines
6
Define 'physiologic antagonism'
Occurs when two drugs acting on different receptors and pathways exert opposing actions on the same system, leading to no net response
7
Define 'efficacy'
the maximum effect of a drug
8
Define 'potency'
The concentration/dose of a drug required to produce 50% of the drug’s maximal effect (EC50). It is used as a comparative measure between drugs where different doses are needed to produce the same effect.
9
Define 'median inhibitory concentration'
The concentration of an antagonist that reduces a specified response to 50% of the maximal possible effect.
10
Define 'hysteresis'
Where the value of a physical property lags behind changes in the effect causing it i.e. the relationship between drug concentration and its effect is not direct
11
Define 'counter-clockwise hysteresis'
The effect can increase with time for a given drug: Sensitisation (up-regulation of receptors), distribution delay to the site of the effect, an agonistic metabolite may be formed, slow receptor kinetics, and time-dependent protein binding
12