Multiple dose pharmacokinetic study of oxolinic acid in cod, Gadus morhua L.

The plasma, muscle and liver distribution and elimination of the antibacterial agent oxolinic acid were studied after multiple oral (p.o.) administration of 10 or 20 mg kg⁻¹ day⁻¹ to cod (Gadus morhua) for 6 days. The fish, held in seawater at 6 and 12°C and weighing 150–250 g were sampled 24 h following last medication. The concentrations in plasma and tissues were clearly dosage and temperature dependent. The distribution from plasma to muscle (muscle/plasma ratio) was higher than that from a single dose study and independent of temperature and dosage. The distribution from plasma to liver (liver/plasma ratio) was lower than the muscle/plasma ratio and according to this study dependent of the administered dosage but independent of temperature. The elimination of oxolinic acid from plasma, muscle and liver was considerably faster following multiple administration compared to a single administration.