logdose

Logdose is a term used in pharmacology and toxicology to denote the logarithm of a dose, typically used as the independent variable in dose-response analyses. Although not always formal, logdose commonly refers to the log-transformed dose value extracted from administration data, often on a base-10 or natural logarithm scale.

Calculation and units: logdose = log10(dose) or log(dose), where dose is the amount delivered (for example, mg, μg, Gy) and must be positive. Zero doses require a small positive floor or be excluded from logarithmic transformation. Values are unit-dependent; when using log-dose, the axis represents orders of magnitude of dose.

Usage in modeling: Transforming dose data to a log scale linearizes many sigmoidal dose-response relationships, facilitating linear or probit/logit modeling and the estimation of parameters such as EC50 or LD50 on the log-dose axis. In Hill-type models, the dose argument is often converted to logdose before fitting.

Applications: Logdose is widely used in pharmacology, toxicology, radiobiology, and ecotoxicology where doses span multiple orders of magnitude and are more interpretable on a log scale. Researchers may report results as logdose values or transform them for model fitting, then back-transform for interpretation.

Considerations: The base of the logarithm affects numerical values but not the underlying relationships; back-transformation is needed to report original doses. Care is needed with zero or negative doses and with inconsistent units across studies.

See also: log-dose, EC50, LD50, probit analysis, logit analysis, Hill equation.