Effect of pH and of Urea on Nitrofurantoin Activity

Abstract

Summary and conclusions

1. The apparent antibacterial activity of nitrofurantoin (pKa 7.2) against E. coli, S. aureus, and Pr. vulgaris is increased as the pH of the medium is lowered. 2. P. aeruginosa becomes susceptible to nitrofurantoin in the presence of 1% or more urea and in an acidic medium (pH 6). 3. Incorporation of 2% NH₄Cl as a urinary acidifier in the diet of rats did not have a major effect on the nitrofurantoin concentrations attained in the urine or on the total amount of nitrofurantoin excreted. 4. The ingestion of a high protein diet by albino rats to increase urea excretion did not adversely affect the urinary concentration nor the total amount of nitrofurantoin excreted. S. Albino rats receiving 0.1% nitrofurantoin (about 10 × calculated human dose) and 2% NH₄Cl in the diet for a 2-week period showed no evidence of crystalluria or kidney pathology.