Circadian pharmacodynamics of anticancer therapies.

Circadian variation in drug metabolism and tissue sensitivity to drugs affects their activity and toxicity. A growing body of data suggests that therapy may be improved and toxicity reduced by administering antineoplastic agents at carefully selected times of the day. Here I briefly review molecular, cellular, and organismic time-keeping mechanisms as well as cytokinetic, pharmacokinetic, and pharmacodynamic data, which support the predictable and exploitable nonlinear dynamic relation between dose and effect that occurs each day.