Adult-Gerontology Clinical Nurse Specialist (CNS) Practice Exam

The measure of the body's ability to eliminate a drug is called what?

1. Afinity

2. Clearance

3. Potency

4. Excretion

The correct answer is: Clearance

Clearance refers specifically to the measure of the body's ability to eliminate a drug from the system. It is a pharmacokinetic parameter that indicates how efficiently a drug is removed from the bloodstream and can be expressed in terms of volume per unit of time (e.g., mL/min). Clearance takes into account factors like renal function, liver function, and blood flow to the organs responsible for drug metabolism and excretion. In the context of drug therapy, understanding clearance is vital for determining appropriate dosing regimens to maintain therapeutic levels without causing toxicity. For instance, a drug with a high clearance rate may require more frequent dosing compared to a drug with a low clearance rate. The other options such as affinity, potency, and excretion are related concepts in pharmacology but do not specifically measure the body's ability to eliminate drugs. Affinity describes the strength of the interaction between a drug and its receptor. Potency indicates the amount of drug needed to elicit a maximal effect. Excretion is the process of removing the drug from the body, which contributes to clearance but does not quantify this capability directly.