Abstract
1. The biliary excretion of demethylchlortetracycline (DMCT) was investigated in rats with ligated renal pedicles. Thin-layer chromatography of bile from rats injected with [14C]DMCT showed the presence of only unchanged compound. After a dose of 10 mg/kg, the bile-to-plasma concentration ratio of DMCT was 29, and 10% of the dose was excreted in 90 min.
2. Probenecid, in a dose 5 times that of DMCT, lowered the biliary concentration of the antibiotic, but did not alter the excretion rate. Tetracycline, in a dose 100 times that of DMCT, markedly depressed the excretion rate of DMCT.
3. DMCT appears to be excreted by a process of active transport.