Which type of response is proportional to concentration and usually reversible?

Which type of response is proportional to concentration and usually reversible?

• A. Graded
• B. Quantal
• C. Threshold-based
• D. All-or-none

Answer: (A)

The main idea is the dose–response relationship in pharmacodynamics, focusing on how a response can be graded within an individual. A graded response increases smoothly with higher drug concentration, producing a continuous range of effect rather than a simple yes/no. This type of response is typically reversible because as the drug is cleared and concentrations fall, the effect diminishes accordingly. In contrast, a quantal response looks at the fraction of a population that responds at a given dose (an all-or-none outcome at the group level), a threshold-based view implies no response below a certain dose with increasing response after that threshold, and an all-or-none pattern describes a binary response within an individual. Therefore, the response that is proportional to concentration and usually reversible is the graded dose–response.

The main idea is the dose–response relationship in pharmacodynamics, focusing on how a response can be graded within an individual. A graded response increases smoothly with higher drug concentration, producing a continuous range of effect rather than a simple yes/no. This type of response is typically reversible because as the drug is cleared and concentrations fall, the effect diminishes accordingly. In contrast, a quantal response looks at the fraction of a population that responds at a given dose (an all-or-none outcome at the group level), a threshold-based view implies no response below a certain dose with increasing response after that threshold, and an all-or-none pattern describes a binary response within an individual. Therefore, the response that is proportional to concentration and usually reversible is the graded dose–response.