Pharmacodynamics

Question 1

Pharmacodynamics

Answer 1

How the drug affects the body:

Efficiency / Potency

Efficacy

Receptor occupancy

Question 2

Drug efficiency/potency

Answer 2

Drug efficiency = receptor binding efficiency

Drug potency determines dosage

e. g. Benzos
* differ in potency, therapeutic effect is the same
* high potency isn’t “better”– simply a different dosage

Question 3

Drug Efficacy

Answer 3

The drug’s maximum possible effects

*NOT the amount needed to produce those effects

E.g.
Drug X reduces depression 50%
Drug Y reduces it 30%.

Drug X is more efficacious, but higher dosage does not result in greater efficacy
(D-R Curve Asymptote)

Question 4

Dose-Response Curve

Answer 4

Minimum: detectable response

Maximum: greatest degree of response that can be achieved with that drug.

Effects of drugs are always influenced by dosage

Different DR Functions
*Same drug at different dosages can target different symptoms

*There is no typical DR function.

Question 5

Therapeutic Index / Window

Answer 5

Ratio ED 50 - LD50

When the maximum therapeutic effect is very close to the margin for adverse effect, you have a higher chance of toxicity

Therefore the greater the separation of curves, the greater the margin of safety, and lower chances of toxicity.

Half-life of drug must be considered in order to manage the therapeutic window and prevent toxicity

Question 6

Agonist

Answer 6

Substance that facilitates post-synaptic effects

3 main ways:

1. Increase production of the NT
   * e.g. destroy degrading enzymes
2. Increase release of NT
   * e.g. bind to autoreceptor, block inhibitory effect
3. Activate receptors on post-synaptic cleft
   Or increase efficiency receptors to NT

Question 7

Antagonist

Answer 7

Substance that inhibits or blocks the post-synaptic effects

3 main ways:

1. Interfere with the release of NT
   * e.g. activate autoreceptor
2. Occupy the postsynaptic receptor, blocking the NT
3. Cause the NT to leak from the synaptic vesicle

Question 8

Metabolic tolerance

Answer 8

Faster metabolism of the drug–a pharmacokinetic mechanism

e.g., alcohol metabolization by hepatic enzymes

Question 9

Cellular-adaptive tolerance

Answer 9

Down-regulation of receptors–a pharmacodynamic mechanism

Question 10

Factors that determine the effect of a drug on an individual

Answer 10

Age

Weight

Setting in which the drug is used

History of use (tolerance)

Level of proteins in blood

Time of day drug is consumed

Question 11

Sensitization

Answer 11

Increase in effect of drug over time

OPPOSITE of tolerance

e.g. marijuana

Question 12

Dependence

Answer 12

Physiological or psychological need to keep taking the drug

Physical Dependence results in withdrawal syndrome
e.g. alcohol, antidepressants, opiates

Question 13

Antidepressant discontinuation syndrome

Answer 13

Anxiety, sleeplessness, flu symptoms and more

More likely to occur with SSRI’s with shorter half lives
*metabolized more quickly, can jolt the system