<unk>  in pharmacokinetics is the ratio of<unk>  (Cmax) and<unk>  (Cmin) levels of a drug over its dosing interval (τ) at steady state.<unk>  (PTR), also known as<unk> -to-trough variation or<unk> -to-trough fluctuation, is a parameter in pharmacokinetics which is defined as the ratio of Cmax <unk>  concentration and Cmin<unk>  concentration over a dosing interval for a given drug. A drug with an elimination half-life of 24 hours taken once per day will have a<unk>  of approximately 2.<unk>  is proportional to half-life and to dosing interval, with longer half-lives and shorter dosing intervals giving smaller ratios.
Peak-to-trough ratio
Minimum alveolar concentration
Dose area product
Equivalent dose
Trough level
Extraction ratio
Standardized uptake value
Biological half-life