LAUSR

Abstract S-(+)-linalool is a phytochemical with proven sedative and anesthetic effects in silver catfish (Rhamdia quelen); however, the pharmacokinetic profile of this compound in fish remains unknown. Therefore, this study describes the pharmacokinetics of S-(+)-linalool in silver catfish anesthetized by immersion bath. Fish were exposed to 153 mg/L S-(+)-linalool for a maximum of 30 min. Blood and brain samples were collected at several time-points up to 4.0 h (0.5 h of anesthesia and 3.5 h of recovery) after the onset of exposure. Before each tissue/blood sampling, the anesthesia stage of each animal was recorded. Following S-(+)-linalool quantification in plasma and brain tissue by gas chromatography with flame ionization, concentration curves were constructed for determination of the pharmacokinetic parameters. S-(+)-linalool in the plasma and brain was detected within the first 2 min (0.03 h) of exposure, with maximum times (Tmax) of 0.50 and 0.33 h and maximum concentrations (Cmax) of 129.33 μg/mL and 113.92 μg/g, respectively. Other parameters estimated for the plasma and brain were terminal half-lives (T1/2β) of 1.36 and 57.27 h, elimination constants (Kel) of 0.50 and 0.01/h, areas under the curve from zero to 4.0 h (AUC0–t) of 120.98 μg/mL/h and 250.57 μg/g/h, and AUCs from zero to infinity (ASC0–∞) of 132.15 μg/mL/h and 4946.13 μg/g/h, respectively. After 10 min (equivalent to a collection time of 0.66 h) in a drug-free bath, all animals recovered from anesthesia. These results suggest that S-(+)-linalool is promptly absorbed into the bloodstream and widely distributed to the brain. Elimination is efficient in plasma but slower in the brain, yet this factor does not impair the recovery of animals, which occurs quickly. Therefore, S-(+)-linalool holds a pharmacokinetic profile suitable for its application as an anesthetic in aquaculture.