Plotting and analyzing drug-receptor RESPONSES

Question 1

Why does the equation for drug EFFECTS follow the same relationship to drug concentration as for binding?

Answer 1

Because it is drug-receptor BINDING that mediates drug EFFECTS

Question 2

Equation for drug effects:

Answer 2

Effect at given concentration divided by maximal effect possible (E/Emax) is PROPORTIONAL to ([D]/EC50+[D])

Question 3

EC50 is ______.

Answer 3

• the concentration of drug that gives half-maximal effect

- takes the place of Kd from the binding equation

Question 4

Drug effects are _____ to receptor occupancy.

Answer 4

Proportional

Question 5

Potency ____.

Answer 5

• the amount of drug required to generate a given fractional response

Question 6

Define potency in regards to EC50, the concentration for 50% of maximal effect.

Answer 6

• low EC50 value indicates a more potent drug (effects at lower concentrations)
• high EC50 indicates a less potent drug (higher concentrations required for same effect)

Question 7

Potentcy applies to both agonists and antagonists. How?

Answer 7

It induces effects in both:
Agonists: INCREASING receptor action
Antagonists: DECREASING receptor action

Question 8

On a receptor EFFECTS/ACTIONS plot, what kind of scale is used?

Answer 8

X-axis: drug concentration on a logarithmic scale

Y axis: percent of maximal effect or response

Question 9

What does a logarithmic scale mean?

Answer 9

distance from 1-1- is same as distance from 10-100, and 100-1000.

Question 10

What kind of curve is generate by logarithmic scale? What are characteristics?

Answer 10

• Sigmoid (S-shaped) curve.
• curve approached 0 and 100% ASYMPTOTICALLY and SYMMETRICALLY
• EC50 is centered on the X-axis in the plot.

Question 11

Why would we use a logarithmic scale?

Answer 11

• a wider range of drug concentrations can be plotted as logs
• convenient for comparing curves for multiple drugs with different Kd and EC50 values
• Most widely used format for dose-response curves

Question 12

Curve further left =

Answer 12

lower EC50 and higher potency

Question 13

Curve further right =

Answer 13

higher EC50 and lower potency

Question 14

Drug concentration conversions:

Answer 14

10-9 = 1, 10-8 = 10, 10-7 = 100, 10-6 = 1000, 10-5 = 10000

Question 15

1 pico (pM) =

Answer 15

-12 log M, [A]

Question 16

1 nano (nM) =

Answer 16

-9 log M, [A]

Question 17

1 micro (uM) =

Answer 17

-6 log M, [A]

Question 18

1 milli (mM) =

Answer 18

-3 log M, [A]