[Circadian rhythms in the urinary excretion of salicylate (chronopharmacokinetics) in healthy adults].

Six healthy adults volunteered to ingest a 1 g solution/24 h of sodium salicylate in a study consisting of 4 standardized tests. The difference between tests was the timing of drug absorption: 07(00), 11(00), 19(00) and 23(00) respectively. The 4 separate tests were performed at least 1 week apart. Subjects; synchronization : diurnal routine activity with light-on at 07(00) and light-off at 23(00) Urine was collected at four-hour intervals, for 48 hours following drug ingestion. By the mean cosinor summary of least squares fits of a 24-hour cosine curve, or by other testing, a within-day difference is established for several chronopharmacokinetic parameters characterizing urinary salicylate excretion. By criteria including the height of the peak excretion, the span necessary to reach the peak, etc., it is shown that, as compared to drug administration at other times, salicylate is excreted faster into the urine, reaches higher values sooner and falls off faster when the drug is ingested between 19(00) and 23(00).