The quantification of the neutralization of the action of antibiotics by cationic iron.

This paper describes the reversal of antibiotic action by iron. Crude measurements of the molar ratio of iron to various antibiotics at reversal indicated that ampicillin, carbenicillin and lincomycin had low ratios of 0.2 to 2.4. With the remainder the ratios lay between 13 and 105; they averaged 46 for the tetracyclines, and 70 for the aminoglycosides. Precise measurement with Fe+++ and tetracycline revealed that the molar ratio for neutralization increased with increasing concentrations of tetracycline; from 1 to 625 mg/l the ratio increased over three-fold from 35 to 118. At the tetracycline concentration of 5 mg/l--usually achieved in plasma during effective therapy--the ratio is of the order of 45.