The Effective Duration of Antimicrobial Activity of Mafenide Acetate After Reconstitution

Mafenide acetate is an effective but costly antimicrobial solution used for burn wounds. The package insert instructs the user to discard unused solution within 48 hours of opening. The purpose of this study is to evaluate the antimicrobial activity of mafenide acetate beyond 48 hours after reconstitution, to possibly reduce cost by eliminating product waste. Staphylococcus aureus and Pseudomonas aeruginosa isolates were used to seed Mueller-Hinton agar plates. Filter paper disks were then saturated with 5% mafenide acetate at 0, 2, 7, 14, 30, and 60 days after reconstitution. Disks were then placed on the seeded agar plates and incubated. After incubation, the zone of inhibition around each plate was measured. A zone of inhibition of 2 mm or greater was indicative of susceptibility. Mafenide acetate remained efficacious, with a zone of inhibition of >2 mm to both organisms at 0, 2, 7, 14, 30, and 60 days after mafenide acetate reconstitution. This in vitro study demonstrates that the antimicrobial activity of mafenide acetate remains present for at least 60 days after reconstitution. Unused mafenide may not need to be discarded at 48 hours after opening. Reducing wasted product has the potential to translate into cost savings.