What are the two main types of plasma concentration versus effect curves?

What are the two main types of plasma concentration versus effect curves?

• A. Graded and quantal
• B. Linear and nonlinear
• C. Time-dependent and time-independent
• D. Immediate and delayed

Answer: (A)

In pharmacodynamics, there are two broad ways to represent how a drug’s effect relates to its concentration. One is a graded curve, which shows a continuous range of effects in a single individual as the plasma concentration rises. This curve increases (or decreases) smoothly and can be described by parameters like EC50 and Emax; it tells you exactly how strong the response is at each concentration. The other is a quantal curve, which looks at a population. It shows the fraction of individuals who achieve a defined effect at each concentration or dose, giving a sigmoidal plot of percent responders versus dose. From this, you can determine measures like ED50, the dose at which 50% of the population responds. So the two main types are graded curves (continuous, in a single subject) and quantal curves (all-or-none responses across a population). The other terms listed don’t capture this fundamental distinction.

In pharmacodynamics, there are two broad ways to represent how a drug’s effect relates to its concentration. One is a graded curve, which shows a continuous range of effects in a single individual as the plasma concentration rises. This curve increases (or decreases) smoothly and can be described by parameters like EC50 and Emax; it tells you exactly how strong the response is at each concentration.

The other is a quantal curve, which looks at a population. It shows the fraction of individuals who achieve a defined effect at each concentration or dose, giving a sigmoidal plot of percent responders versus dose. From this, you can determine measures like ED50, the dose at which 50% of the population responds.

So the two main types are graded curves (continuous, in a single subject) and quantal curves (all-or-none responses across a population). The other terms listed don’t capture this fundamental distinction.