Renal excretion of nitrofurantoin (Furadantin)

¹ Section of Biology, Eaton Laboratories, Division of the Norwich Pharmacal Company, Norwich, New York

Renal clearance of nitrofurantoin at various plasma levels was determined in the white rat. The clearance ratios (nitrofurantoin/inulin) exhibited a curvilinear relationship with the plasma level of the drug. The excretion of nitrofurantoin was found to be dependent upon the three following factors: glomerular filtration, tubular secretion and tubular reabsorption. The clearance of nitrofurantoin was not affected by urine flow nor by concurrent PAH administration. It was increased by acetazolamide and decreased slightly by probenecid. Thirty to forty per cent of the dose was recovered in the urine of rats or dogs after either per oral or intravenous administration. Rapid distribution of the drug was indicated by low plasma concentrations following intravenous administration.