Increase of thiopental concentration in tissues of the rat due to an anesthesia with halothane.
In rats anesthetized with halothane (CAS 151-67-7) (1.5 vol%) and rats without any further treatment (control) the early distribution phase of thiopental (CAS 76-75-5) (i.v. 30 mg/kg) was studied. In serum and 8 tissues thiopental concentration (T) was determined using ultraviolet detection at 305 nm after extraction and TLC. In rats anesthetized with halothane, T in serum was significantly higher during the 30 min following the thiopental injection (at least +27% and maximally +51%) as compared to the control (same dose), and several pharmacokinetic parameters (e.g. central volume of distribution) were found to be changed thereby; furthermore, at 3, 10 and 30 min T was significantly increased in liver, brain, heart, lung and spleen; in kidney and skeletal muscle a rise of T was also seen, however, it occurred later (after 10 and 30 min). T in fat tissue increased time-dependently; a T-difference in adipose tissue between both groups was not observed. Thiopental was "trapped" during the early distribution phase to a considerable extent in the vessel-rich tissues of rats simultaneously anesthetized with halothane; this pharmacokinetic interaction might be explained hemodynamically: in many tissues regional blood flow is reduced by halothane; thereby a delayed "washout" of thiopental from the vessel-rich tissues could take place and redistribution would be delayed; additional factors as e.g. an increased binding of thiopental at tissue proteins could also play a role. An unusually high T was found at least temporarily in myocardial tissue due to this interaction between the two anesthetics.
Clinic of Anesthesiology and Intensive Care Medicine, University of the Saarland, Homburg, Fed. Rep. of Germany.
U
U
Büch
P
P
Altmayer
J C
JC
Isenberg
H P
HP
Büch
D000758:Anesthesia; D000818:Animals; D002855:Chromatography, Thin Layer; D004347:Drug Interactions; D005045:Etomidate; D005260:Female; D006221:Halothane / Q000494:pharmacology*; D009609:Nitrous Oxide; D051381:Rats; D011919:Rats, Inbred Strains; D013056:Spectrophotometry, Ultraviolet; D013874:Thiopental / Q000493:pharmacokinetics*; D014018:Tissue Distribution; D014673:Vecuronium Bromide
D014673:Vecuronium Bromide; D013874:Thiopental; D009609:Nitrous Oxide; D006221:Halothane; D005045:Etomidate