To prepare the ointment of antibiotic negamycin (NGM), the release behavior from various ointment bases, antimicrobial activity, and chemical stability of NGM were investigated. In vitro release of NGM from gel base was greater than that from hydrophilic ointment JPX and white petrolatum containing 5 w/w% liquid paraffin. The release rate and the amount of NGM released from the gel base were found to increase in proportion to the content of Hiviswako No.104 in the ointment. NGM was much more stable in gel base than in hydrophilic ointment JPX, though it was decomposed under pseudo-first-order kinetics in both ointment bases. Antimicrobial activity of NGM ointment was evaluated by the cup-plate method, suggesting a sufficient efficacy of NGM for the treatment of infectious diseases caused by gram-positive or gram-negative bacterium. The present data suggest the possible utility of gel base in preparation of NGM ointment.
