Rhythmic Variations of Pharmacokinetic Processes of Cyproterone Acetate in Rabbits

• Published in: Biological rhythm research 2001-10, Vol.32 (4), p.401-411
• Main Authors: Boggio, J.C., Encinas, T., Rodríguez, C., Valtorta, S.E., Ros Rodríguez, J.M., San Andrés, M.I.
• Format: Article
• Language: English
• ISSN: 0929-1016; 1744-4179
• DOI: 10.1076/brhm.32.4.401.1334

A study about the influence of administration time on pharmacokinetics of Cyproterone acetate in rabbits was performed. Thirty animals were distributed in six groups, each corresponding to a different time: 2, 6, 10, 14, 18 and 22 hours after light onset (HALO). Rabbits received a single intravenous administration of 4 mg kg -1 Cyproterone acetate. Blood samples were taken and processed by high performance liquid chromatography. Plasmatic data were fitted to a biexponential equation. Concentration at zero time (Co), concentration at zero time extrapolated from the distribution phase (A), hybrid constant for distribution phase and its half life, volume of the central compartment (V c ), volume of distribution at steady state (V ss ), constants for transferring the drug from the central compartment to the exterior (K 10 ) and from the central to the peripheral compartment presented chronobiological variations (p < 0.05) and were fitted to a cosine equation. The following parameters adjusted to circadian rhythms: Co (Acrophase: 1.72 HALO); A (Acrophase: 4.09 HALO); V c (Acrophase: 11.92 HALO); V ss (Acrophase: 10.12 HALO) and K 10 (Acrophase: 3.59 HALO). It was concluded that pharmacokinetics of intravenously injected CPA in rabbits would behave in a different, though predictable, manner according to the animal's biological clock.