Pharmacokinetic data have rhythms: are they important?

Large literature is available to support the statement that both pharmacokinetics and the susceptibility of any biosystem to drugs depend on the body's biological rhythms as well in animals as in man. There are rhythmic alterations in the drug bioavailability, metabolic processes, excretion, receptor sensitivity and pharmacologic action with peaks separated by around 24 h (i.e. circadian rhythms). In medical practice majority of the orally applicable drugs are usually administered according to the scheme "3 times daily". The arguments to administer the drug in dosi refracta are weak and validity of this formula in modern-day medicine with respect to pharmacokinetics and chronobiology will be discussed.