In the context of dose-response relationship of a drug, at some low dose, the lowest dose at which an effect on the response system being monitored is observed is called the threshold dose.
The threshold dose is the lowest dose of a drug or chemical that produces a measurable effect on the response system being monitored. It is the point at which the response to the drug or chemical begins to deviate from the baseline response, which is the response in the absence of the drug or chemical.
The threshold dose is an important concept in toxicology and pharmacology, as it helps determine the safety and efficacy of drugs and chemicals. The threshold dose is used to establish safe exposure limits for chemicals, such as air pollutants or food additives, and to determine the effective dose range for drugs.
Below the threshold dose, there is no observable effect on the response system being monitored. Above the threshold dose, the response to the drug or chemical increases in a dose-dependent manner, until a maximum effect is reached at the maximum response dose. The dose-response relationship between the threshold dose and the maximum response dose is typically represented by a dose-response curve, which is used to determine the pharmacological or toxicological properties of the drug or chemical.
In summary, the threshold dose is the lowest dose of a drug or chemical that produces a measurable effect on the response system being monitored. It is an important concept in toxicology and pharmacology, as it helps determine the safety and efficacy of drugs and chemicals and is used to establish safe exposurelimits and effective dose ranges.