[The effect of age on pharmacokinetic parameters of oxytetracycline and rolitetracycline in rabbits].

The effect of rabbit age in the Californian White breed was investigated on oxytetracycline and rolitetracycline concentrations in the blood serum and soft tissues, and on the biological half-life of the given antibiotics. The animals were at the age shortly before sexual maturity or they had reached sexual maturity. Oxytetracycline was administered in form of the preparation Oxymykoin inj. a. u. v. Spofa and roliteracycline nitrate in form of the preparation Rolitetracycline inj. Spofa. These tetracyclines were administered intramuscularly at a single dose of 20 mg per kg liveweight. In comparison with adult animals, in young rabbits the starting concentrations of the two tetracyclines in the blood (first hour) were statistically insignificantly higher; they were resorbed in the systemic circulation in a shorter time and were excreted faster from the blood (mainly oxytetracycline). The significantly lower serum concentrations were recorded in the 6th, 12th and 24th hour after oxytetracycline administration, and in the 12th and 24th hour after rolitetracycline administration. At the same time a decrease was observed in the concentrations of the two oxytetracyclines in the organs and muscles of young animals.