title: Chronobiological variations of indomethacin pharmacokinetic parameters in sheep.
abstract: A two-phase study to investigate the influence of administration time on pharmacokinetics of indomethacin in sheep was performed. In phase I, 12 animals were allocated to four groups, each corresponding to a different time: 08:00, 14:00, 20:00, 02:00 h. Sheep received an intravenous administration of 1 mg/kg indomethacin. In phase II, each group was administered indomethacin with a 12-h difference compared to Phase I. The trial was performed in autumn, and animals were subjected to a natural light:dark cycle of 10:14 h. Blood samples were taken and processed by high performance liquid chromatography (HPLC) with ultraviolet detection. For each pharmacokinetic parameter, an analysis of variance was performed to outline the existence of chronobiological variations. Concentration at zero time (C0), hybrid constant for distribution and its half life, hybrid constant for elimination and its half-life, volume of distribution (V(d)), area under the curve (AUC(infinity)) and clearance rate (Cl), presented chronobiological variations (P < 0.05) and were fitted to a cosine equation. The following parameters adjusted to circadian rhythms: C(0) (acrophase: 13.9788 h); AUC(infinity) (acrophase: 13.4377 h); V(d) (acrophase: 0.8245 h) and Cl (acrophase: 1.4965 h). It was concluded that pharmacokinetic parameters of intravenously injected indomethacin in sheep would behave in a different, though predictable, manner according to the animal's biological clock.
authors.affiliation: Cátedra de Farmacología, Facultad de Ciencias Veterinarias, Universidad Nacional del Litoral, R.P. Kreder 2805 (3080) Esperanza, Santa Fe, Argentina. jcboggio@fcv.unl.edu.ar
authors.forename: J C
authors.initials: JC
authors.lastname: Boggio
authors.forename: S E
authors.initials: SE
authors.lastname: Valtorta
authors.forename: S
authors.initials: S
authors.lastname: Sánchez
authors.forename: Q
authors.initials: Q
authors.lastname: McKellar
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D019540:Area Under Curve; D002851:Chromatography, High Pressure Liquid; D002909:Chronobiology Phenomena; D002940:Circadian Rhythm; D018592:Cross-Over Studies; D007213:Indomethacin / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D007275:Injections, Intravenous; D008297:Male; D011897:Random Allocation; D012756:Sheep / Q000378:metabolism*
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D007213:Indomethacin