Biological activity of polynoxylin--an insoluble urea-formaldehyde condensation product.

The antimicrobial activity of polynoxylin, an alkali urea-formaldehyde condensation product, has been examined. The minimum inhibitory concentration (MIC) for 1000 clinical isolates of bacteria and yeasts was in the range 1024-16,384 mg/l. Cidal concentrations of the drug were within one dilution of the corresponding values for MIC, the results suggest a cumulative mode of antimicrobial activity. Formaldehyde, the putative active component of polynoxylin, was released into water from 10% (w/w) cream preparation which gave a maximum yield of 1.56 mg within 6 h. The limited water solubility of polynoxylin, cumulative mode of antimicrobial action and presence of pre-formed formaldehyde in the pharmaceutical preparation, suggest the possibility of sustained activity when applied to skin. The slow solubilization of particulate polynoxylin and gradual liberation of inhibitory degradation products may further enhance the inherent antimicrobial activity afforded by the presence of pre-formed formaldehyde.