Lecture 1 Pharmacodynamics Flashcards
Drug Receptor
Specific macromolecule that recognizes the drug
What is required for drug to affect a specific action?
Drug Receptor
Ability for drug to bind depends on which two factors?
- drug size
- shape relative to binding site
Degree of affinity
degree of attraction or binding power a given drug has for the receptors
Receptor
component on or within a cell that a substance can bind to
Receptors on the cell surface
- Receptor sites on exterior of cell
- Will not specifically allow substance to enter cell
- Receptors are “transmembrane” proteins: Relay information from binding site to intracellular mechanism to cause change
Proteins may have which two sites
- extracellular receptor site: binding domain
- intracellular enzymatic component: catalytic domain
Example of insulin
- Binds to extracellular component of protein
- Activates protein enzymatic activity on inner surface of cell membrane
- Leads to glucose uptake in muscle cells
Affinity
- Amount of attraction between the drug and the receptor
Selective
- a type of drug that affects only one type of cell or tissue and produces a specific physiological response
- no drug produces only one effect
- example: Cardioselectivve drugs vs. GI system
Dose Response
- Shape of curve is related to number of receptors bound by the drug
- Response is proportional to number of receptors occupied by the drug
What happens as dosage increases?
- more receptors become occupied
- Dose response increases
Agonist drug
- binds to a receptor and produces an action
- Affinity and efficacy
Antagonist drug
- binds to a receptor and does not produce an action
- Only affinity
- can be called a blocker
example: Benadryl
Partial Agonists
- do not evoke a maximal response
- often have high affinity for a receptor
- may not completely activate the receptor
Agonist-Antagonist
- can stimulate certain receptors while blocking effects of endogenous substances on other receptors
- example: SERMs
Inverse agonists
- bind to the same receptor as the agonist but have the opposite effect on cell function
- *opposite effect but same receptor
Receptor Regulation
- not static
- regulated by exogenous and endogenous factors
- can decrease and increase their sensitivity to stimulation
Overstimulation of postsynaptic receptors may lead to?
- functional decrease in appropriate receptor population
- endogenous: Neurotransmitters/ Hormones
- exogenous: Medications
Result of Receptor Desensitization
Cell becomes less responsive
Receptor Desensitization: “Down-Regulation”
- slower, more prolonged process in which the number of available receptors is diminished
Prolonged exposure of Receptor Desensitization can cause?
- Receptor removal
- Decreased receptor synthesis
- Combination of both
Receptor Desensitization or Decrease in receptor function can protect against?
- Acute CNS injury
- Cardiac diagnoses
- Viral infections
