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One percent silver sulfadiazine has been commonly used as a topical antimicrobial agent after a burn injury. Incidence of burn wound colonization by Staphylococcus aureus in patients treated with silver sulfadiazine has spurred research for other agents. A topical preparation that contains zinc and sulfadiazine (Zad-G) was evaluated for in vitro antibacterial spectrum and in vivo efficacy. Muscle biopsy specimens of rats treated with Zad-G appear to have fewer colonies of S. aureus than groups treated with silver sulfadiazine. Topical therapy with Zad-G for patients with burns was comfortable, reduced wound infection, and was comparable to therapy with silver sulfadiazine. A topical Zad-G preparation that contains zinc sulfadiazine appears to be an effective alternative to silver sulfadiazine in the treatment of burn wounds.

The apparent efficacy of zinc and cerium sulfadiazine and the metabolic role of other trace metals suggested that sulfonamide salts of these might be of therapeutic value. There is also a possibility that metal salts of other sulfonamides might be useful. Accordingly other sulfonamide salts of zinc were prepared and studied in vitro and in vivo. Only zinc sulfathiazole and zinc methoxazole were as effective as zinc sulfadiazine in animal studies. The sulfadiazines of aluminum, chromium, cobalt, copper and iron were prepared and compared in vitro and in vivo. Only cobalt sulfadiazine appeared comparable to zinc and cerium sulfadiazine in healing burn wounds in rats. Studies on the molecular structure of silver sulfonamides disclosed the polymeric structure peculiar to silver sulfadiazine which appears to account for its unique properties. It is not yet known whether other metal sulfadiazines have this attribute.

Silver sulfadiazine (Silvadene, U.S.; Flamazine, U.K.; Flammazine, N.; Sulplata, S.A.) is the newest topical antimicrobial agent available following worldwide clinical trials. Good control of infection is achieved without pain or other demonstrable side effects, using either dressings or the exposure technic. Many burned areas kept free of infection heal without grafting. Where necessary, early preparation for and good take of grafts has been attained by utilizing this new therapeutic agent. Markedly reduced mortality from burn wound sepsis has generally been observed.

Silver sulfadiazine (Silvadene(R), US; Flamazine UK; Flamazine, Netherlands; Sulplata South America) is proving to be a highly successful topical antimicrobial agent for control of burn wound infections. The advantages of wide spectrum of activity, painless application, negligible toxicity and ease of application contribute to the usefulness of this compound. These advantages have led to its use for wound infections other than burns, for skin ulceration and for certain dermatologic lesions; also for the prevention and treatment of various vaginal infections. Described also are zinc sulfadiazine which can provide zinc for wound healing and cerous sulfadiazine which contains the rare earth metal cerium. Their unique effects on cell biology may determine their specific roles in topical therapy.

Silver sulfadiazine-resistant organisms are arising at an irregular rate and may eventually interfere with wound management. To counter this problem several new antibacterial agents were tested in combination with silver sulfadiazine. Only sodium piperacillin (Pipracil, Lederle) exhibited synergism with silver sulfadiazine both in vitro (against various species of organisms) and in burned animals. The MIC of AgSD and Pipracil was 50 nmole/ml and 250 nmole/ml, respectively, but a combination of 6 nmole/ml of AgSD and 7.5 nmole/ml of Pipracil inhibited the growth of Pseudomonas aeruginosa. In burned mice infected with either AgSD-resistant or sensitive strains, the mortality in groups receiving combinations of topical Pipracil and silver sulfadiazine was 0-10%; in contrast, treatment with Pipracil or silver sulfadiazine alone resulted in much higher mortality. Thus it would appear that a combination of silver sulfadiazine and Pipracil, each of which have long been used in patients topically and parenterally, may prove valuable in patients with burn wound infections related to or caused by organisms resistant to silver sulfadiazine.

Sulfadiazine silver-resistant strains of Pseudomonas aeruginosa isolated from burned patients from several countries are sensitive to sulfadiazine silver in vitro, but in burned mice and rats resist topical therapy with sulfadiazine silver. In searching for an effective topical agent against these resistant organisms, we found that FPQC (1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7[1-piperazinyl]-quinoline-carboxylic acid) and its silver salt are effective both in vitro and in vivo. In vitro, their minimal inhibitory concentrations are ten to 20 times lower than that of sulfadiazine silver. In burned mice infected with resistant Pseudomonas strains, mortality in groups receiving topical therapy with FPQC or FPQC silver is 0%, but 80% to 100% with sulfadiazine silver and 100% without treatment. Similar results were obtained in burned rats. The efficacy of FPQC and FPQC silver in vivo may represent discovery of new agents of known low toxicity that are useful in topical burn therapy.