Effects of Blood Levels of Tetracycline and Oxytetracycline on Hepatic and Renal Functions in Normal Subjects

Abstract

A study was conducted on 20 young healthy male patients to compare the antibiotic serum levels and urinary excretion of tetracycline and oxytetracycline after two 500-mg doses daily for 5 days. After a single dose of 500 mg, the serum antibiotic levels of tetracycline and oxytetracycline were almost similar for the next 12 h and were still significantly higher than the minimum inhibitory concentration (0.5 μg/ml). In contrast, 5 days study of serum antibiotics revealed very significantly elevated tetracycline levels compared to oxytetracycline. Tetracycline also showed a higher cumulative effect after stoppage of therapy for the next 36 h against 24 h in the case of oxytetracycline. Urinary excretion studies have shown that oxytetracycline is excreted more rapidly and in higher concentration than tetracycline and this may account for superiority of oxytetracycline for treatment of urinary tract infections.