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Systemic absorption of water-soluble and water-insoluble drugs through human burn wounds was compared. Serum levels of sulphadiazine were estimated after application of silver sulphadiazine (water-insoluble) cream, sulphadiazine (water-insoluble) cream and sodium sulphadiazine (water-soluble) cream. It was found that the absorption of sodium sulphadiazine was greater than that of sulphadiazine or silver sulphadiazine.

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.

Although silver sulfadiazine has been used extensively as an effective topical antimicrobial agent in thermal injury patients, little is known about the cutaneous absorption of the silver moiety in these patients. Therefore, we longitudinally evaluated both serum silver concentration and 24-hour urinary excretion of silver in 23 patients with second- and third-degree thermal burns. Mean serum silver concentrations were modestly elevated throughout the patients' hospital course. Urinary excretion of silver was markedly elevated, especially in those patients with more severe burns. Indeed, in patients who had burns covering more than 60% of the total body surface area mean peak silver excretion was 1100 micrograms/24 hr (normal, less than 1 micrograms/24 hr). Thus, silver ion is absorbed across the burn wound in thermal injury patients treated with silver sulfadiazine. The 24-hour urinary excretion of silver appears to be a very sensitive indicator of cutaneous absorption in these patients. Possible implications of this cutaneous silver absorption warrant further evaluation.

The effect of topical application of silver sulfadiazine cream on the natural killer (NK) cell cytotoxicity was studied in a rat model of thermal injury. The rats were given a 30% total body surface area scald injury and the NK cell cytotoxicity was studied in rats at different days postinjury with or without treatment with silver sulfadiazine. The NK cell activity was observed to be significantly (P less than .0025) suppressed at day 7 postinjury in nontreated burned rats compared with control sham burned animals. Interestingly, in rats treated with silver sulfadiazine twice daily, no suppression in NK cell activity was observed. The application of base cream (without silver sulfadiazine) did not have any significant effect on the NK cell activity in burned rats. The data show that the effect of silver sulfadiazine on NK cell activity may be due to the sulfadiazine component, since the serum levels of sulfadiazine (33.7 +/- 1.9 micrograms/dL) were observed to be maximal at day 7 postinjury.

This report demonstrates prolonged effective release of silver sulfadiazine (AgSD) to experimental burns in rats from a solid dressing by mixtures of polyethylene glycol-400 and poly-2-hydroxyethyl methacrylate. The synthetic dressing, incorporating the antimicrobial drug, may be formed either directly on the burn wound or prepared as a preformed sheet and applied to the wound after it was contaminated with bacteria. The level of silver in the blood following treatment of the burn wound with topical AgSD (Silvadene, Marion Labs) is significantly less when the drug is presented in the dressing than when the drug is applied in a cream base; the concentration of the sulfadiazine moiety in the blood is similar for the two drug preparations. Improved survival of the burned and contaminated rats and reduced nursing care were observed in the burned animals when the synthetic dressing was used to deliver the drug relative to the results when the AgSD was applied in a cream base by standard procedures.