Pharmacodynamics Flashcards Preview

Year 3: CSP & PH > Pharmacodynamics > Flashcards

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

Define 'clockwise hysteresis'

The measured effect decreases with time for a given drug concentration e.g. tolerance (down-regulation of receptors), disequilibrium between arterial and venous circulation, generation of an antagonistic metabolite, feedback regulation, time-dependent protein binding