Receptor binding
Frequency distribution curves and quantal concentration-effect and dose-effect curves.
A. Frequency Distribution Curves. An experiment was performed on 100 subjects, and the effective plasma concentration that produced a quantal reponse was determined for each individual. The number of subjects who required each dose is plotted, giving a lognormal frequency distribution (colored bars). The gray bars demonstrate that the normal frequency distribution, when summated, yields the cumulative frequency distribution - a sigmoidal curve that is a quantal concentration-effect curve. B. Quantal Dose-Effect Curves. Animals were injected with varying doses of sedative-hypnotic, and the responses determined and plotted. The calculation of the therapeutic index, the ratio of the LD50 to the ED50, is an indication of how selective a drug is in producing its desired effects relative to its toxicity.