Apodoses

Apodoses is a term used in pharmacology and toxicology to denote the dose of a substance that is sufficient to produce a predefined effect. The apodose is defined with respect to a specified level of response on a dose–response curve, such as the dose that yields 50% of the maximal effect (the ED50) or other percentiles like ED90 or TD50. The plural apodoses refers to the corresponding doses for different effects, substances, species, or study conditions.

The term is encountered in older or more traditional pharmacology literature, and in contemporary practice it is more common to refer to specific measures such as EDx, TDx, or LDx to indicate the dose associated with a chosen effect or toxicity. Nevertheless, apodoses remain a conceptual way to discuss the relationship between dose and effect as represented on dose–response curves.

Determination of apodoses involves dose–response experiments, often in animals or humans, with data fitted to a sigmoidal or Hill-type model. The resulting apodose is the dose that achieves the target response, acknowledging that estimates carry uncertainty. Apodoses depend on factors such as route of administration, timing, and population characteristics, and they can vary between individuals due to pharmacokinetic and pharmacodynamic variability.

Applications include comparing potencies between compounds, guiding dose selection in regimen design, and interpreting toxicology data. Limitations include interindividual variability, extrapolation from non-human data, and the dependence of the apodose on study conditions. See also ED50, LD50, TD50, and dose–response curve.