Time-Concentration Curve

The graphical representation of the relationship - for a given drug and a given biological system - between concentration (or dose) and latency or latent period: the period of time elapsing between the time the dose is administered and the time a given effect is produced. Time-concentration curves tend to be hyperbolic
in form: as dose increases latency decreases and vice versa. Latency is an inverse function of concentration. But the hyperbolic relationship never approaches the axes as asymptotes; there is always a concentration below which the drug is ineffective, regardless of the duration of exposure of the tissue to the drug, and there is always a finite interval between the time of exposure to
the drug and the time the response occurs. The time-concentration curve is analogous to the strength-duration curve which the physiologist uses to determine rheobase and chronaxie. It is characteristic of true drug effects that a generally hyperbolic relationship exists between dose and latency. If, with increasing doses of material, a time-concentration curve and a dose-effect curve cannot be demonstrated, one cannot conclude that the material is responsible for the effects observed.

Cf. Dose-Effect Curve, CT Index, Latent Period