For a Type I dose–response curve, which statement is true?

For a Type I dose–response curve, which statement is true?

• A. X-axis is drug dosage; Y-axis is response; curve can be hyperbolic or sigmoidal.
• B. X-axis is receptor occupancy; Y-axis is response; curve can be sigmoidal.
• C. X-axis is time; Y-axis is dose; curve is exponential.
• D. X-axis is dose; Y-axis is receptor occupancy; curve is linear.

Answer: (A)

The main idea being tested is how the pharmacodynamic effect relates to the drug dose in a Type I dose–response curve. In this type of plot, the dose is placed on the x-axis and the observed response on the y-axis. As the dose increases, the response rises toward a maximum; depending on the binding dynamics, the curve can be hyperbolic (simple, non-cooperative binding) or sigmoidal (cooperative binding or amplification). This makes the statement accurate because it describes the standard dose–response relationship with those two possible shapes. Plotting receptor occupancy on the x-axis or switching axes (time versus dose, occupancy versus dose) describes different relationships and is not the classic Type I dose–response depiction.

The main idea being tested is how the pharmacodynamic effect relates to the drug dose in a Type I dose–response curve. In this type of plot, the dose is placed on the x-axis and the observed response on the y-axis. As the dose increases, the response rises toward a maximum; depending on the binding dynamics, the curve can be hyperbolic (simple, non-cooperative binding) or sigmoidal (cooperative binding or amplification).

This makes the statement accurate because it describes the standard dose–response relationship with those two possible shapes. Plotting receptor occupancy on the x-axis or switching axes (time versus dose, occupancy versus dose) describes different relationships and is not the classic Type I dose–response depiction.