[Circadian rhythm in the sensitivity of target systems to drugs: an underestimated phenomenon].

The chronokinetics of a drug corresponds to dosing time-dependent and predictable (rhythmic) changes in parameters used to characterize its pharmacokinetics e.g. Cmax, t(max), t1/2, AUC, etc.) The chronesthesy or chronopharmacodynamics corresponds to circadian changes in susceptibility of target biosystems to this drug. The target system can be an organ or a tissue (skin, bronchial tree, etc.) as well as a receptor, a membrane, an enzymatic process. Both theoretical and practical implications of chronesthesy have been underestimated and even ignored. It is usually assumed that the constant level over time of a drug in the plasma should result in constant effects. Much experimental evidence have shown that this hypothesis must be rejected.