Pharmacodynamics-3: Drug-Receptor Interaction

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20 Questions

What is the drug concentration which achieves 50% of the maximum effect called?

EC50

Which drug has the highest affinity according to the given text?

Fentanyl

What type of drug binds to the receptor but does not cause a cellular response?

Antagonist

What happens to the efficacy of a full agonist when combined with a noncompetitive antagonist?

It decreases

According to the given text, what is the factor affecting affinity?

Receptor density

What is the mathematical relationship that defines the dissociation constant (Kd)?

Kd = Koff / Kon

What determines the concentration of a drug around the receptor needed to form a certain number of drug-receptor complexes?

Drug affinity

What follows the law of mass action in drug-receptor interaction?

Effect

What is the capacity to activate a receptor called in drug-receptor interaction?

Drug efficacy

What determines the fraction of receptors at each state during equilibrium in drug-receptor interaction?

Dissociation constant

What determines the fraction of receptors at each state during equilibrium in drug-receptor interaction?

Dissociation constant

What is the mathematical relationship that defines the dissociation constant (Kd)?

Kd = [R] [D] / [DR]

Which factor affects the drug affinity in drug-receptor interaction?

Kon rate of association

What happens to the efficacy of a full agonist when combined with a competitive antagonist?

Decreases

What type of drug binds to the receptor but does not cause a cellular response?

Antagonist

What is the effect of a competitive antagonist on the dose-response curve of a full agonist?

Parallel right shift

Which drug is an example of a partial agonist acting as an antagonist in the presence of an agonist?

Aripiprazole

What determines the maximal efficacy of a partial agonist?

Maximal efficacy of the full agonist

What is the main difference between a competitive and a noncompetitive antagonist?

Competitive antagonist competes for the agonist-binding site

What is the effect of a noncompetitive antagonist on the efficacy of a full agonist?

Vertical shift downwards

Study Notes

Drug-Receptor Interaction

  • The drug concentration that achieves 50% of the maximum effect is called EC50.

Types of Drugs

  • A drug that binds to the receptor but does not cause a cellular response is called an antagonist.
  • A partial agonist is a drug that binds to the receptor and causes a cellular response, but with lower efficacy than a full agonist.
  • An example of a partial agonist acting as an antagonist in the presence of an agonist is the drug buspirone.

Affinity and Dissociation Constant

  • The factor affecting affinity is the strength of binding between the drug and the receptor.
  • The mathematical relationship that defines the dissociation constant (Kd) is Kd = [R] [D] / [RD], where [R] is the concentration of receptors, [D] is the concentration of drug, and [RD] is the concentration of drug-receptor complexes.

Receptor Binding

  • The concentration of a drug around the receptor needed to form a certain number of drug-receptor complexes is determined by the law of mass action.
  • The law of mass action states that the rate of a reaction is proportional to the concentrations of the reactants.

Receptor Activation

  • The capacity to activate a receptor is called efficacy.
  • The fraction of receptors at each state during equilibrium is determined by the affinity and efficacy of the drug.

Antagonists

  • A competitive antagonist increases the EC50 of a full agonist, shifting the dose-response curve to the right.
  • A noncompetitive antagonist decreases the efficacy of a full agonist, without changing the EC50.
  • The main difference between a competitive and a noncompetitive antagonist is that competitive antagonists bind to the same receptor as the agonist, while noncompetitive antagonists bind to an allosteric site.

Test your understanding of drug-receptor interaction in pharmacodynamics with this quiz. Explore concepts such as drug-receptor complex formation, the law of mass action, drug affinity, and drug efficacy.

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