Physico-chemical properties and biological activities of erythromycin nalidixate.

Erythromycin nalidixate was prepared by combining nalidixic acid with erythromycin base. Thin-layer chromatographic studies and infrared absorption spectrum confirmed homogeneity of the new salt. The salt is very soluble in nonpolar solvent and freely soluble in polar solvent. The salt is quite stable at room temperature (30 +/- 1 degrees C). The antimicrobially active dose of the salt was found to be 820 micrograms/mg. Serum protein binding amounted to 85% and was reversible. LD50 in mice was found to be 371.5 mg/kg when the intraperitoneal route was used.