The ___________________ is the length of time that a medication concentration is sufficient in the blood to produce a therapeutic response

a. Half-life
b. Duration of action
c. Efficacy
d. Affinity

b
Rationale: a. Half-life is the time required for one-half of the dose of a medication to be removed from the body.
b. Correct.
c. Efficacy is the ability of a drug to produce the expected response.
d. Affinity is the force of attraction between a drug and its receptor site.