L.9 Pharmacodynamics

Question 1

Potency

Answer 1

( EC 50 ) of a drug is the concentration at which the drug elicits 50% of its maximal response .

Question 2

Efficacy

Answer 2

• Emax
• the maximal response produced by the drug .

Question 3

Quantal Dose–Response

Answer 3

• The quantal dose–response relationship plots the fraction of the population that responds to a given dose of drug as a function of the drug dose.
• describe the concentrations of a drug that produce a given effect in a population

Question 4

Graded dose–response curves

Answer 4

demonstrate the e ect o a drug as a function of its concentration

Question 5

Agonists

Answer 5

An agonist is a molecule that binds to a receptor and stabilizes the receptor in a particular conformation (usually, the active conformation).

Question 6

Antagonists

Answer 6

• An antagonist is a molecule that inhibits the action of an agonist but has no effect in the absence of the agonist.

Question 7

A receptor antagonist

Answer 7

• binds to either the active site (agonist binding site) or an allosteric site on a receptor.
• Binding of an antagonist to the active site prevents the binding of the agonist to the receptor
• Binding of an antagonist to an allosteric site either alters the Kd or agonist binding or prevents the conformational change required for receptor activation.

Question 8

nonreceptor antagonist

Answer 8

does not bind to the same receptor as an agonist, but it nonetheless inhibits the ability of an agonist to initiate a response.

Question 9

Chemical antagonists

Answer 9

inactivate an agonist before it has the opportunity to act (e.g., by chemical neutralization)

Question 10

physiologic antagonists

Answer 10

cause a physiologic effect opposite to that induced by the agonist.

Question 11

Competitive antagonist

Answer 11

• binds reversibly to the active site of a receptor.
• does not stabilize the conformation required or receptor activation ⇒ the antagonist blocks an agonist from binding to its receptor, while maintaining the receptor in the inactive conformation.

Question 12

Noncompetitive Receptor Antagonists

Answer 12

• bind to either the active site or an allosteric site of a receptor.
• A noncompetitive antagonist that binds to the active site of a receptor can bind either covalently or with very high affinity; in either case, the binding is effectively irreversible.

Question 13

Partial Agonists

Answer 13

is a molecule that binds to a receptor at its active site but produces only a partial response, even when all of the receptors are occupied (bound) by the agonist.

Question 14

Inverse Agonists

Answer 14

acts by abrogating this intrinsic (constitutive) activity of the free (unoccupied) receptor .

Question 15

Spare Receptors

Question 16

Therapeutic Index

Answer 16

the range of doses (concentrations) of a drug that elicits a therapeutic response, without unacceptable adverse effects (toxicity), in a population of patients.