Piritetrate (M-732), a new topical
antifungal agent belonging chemically to the
thiocarbamates, was demonstrated to possess a potent selective antidermatophytic activity. In terms of its MICs in susceptibility testing, mainly done by using Sabouraud
dextrose agar plates,
piritetrate exhibited several- to 10-fold-stronger antidermatophytic activity than
tolnaftate, a reference
thiocarbamate. Furthermore,
piritetrate was found to show a broader antifungal spectrum than
tolnaftate; relatively many species and strains of dematiaceous fungi, dimorphic fungi, and some other filamentous fungi as well as a few strains of Cryptococcus neoformans were fairly susceptible to
piritetrate, while almost all the tested species and strains were resistant to
tolnaftate. All the tested species of the genus Candida were, however, resistant to both compounds. Variables which can influence antimicrobial activity caused few changes in the MICs of either compound against Trichophyton mentagrophytes; however, an increase in the inoculum size resulted in a significant increase in the MICs. The antidermatophytic activities of
piritetrate and
tolnaftate were fungistatic but not fungicidal.
Piritetrate also exhibited a more potent in vitro
anti-T. mentagrophytes activity than
clotrimazole or
tolciclate.
Piritetrate and
tolnaftate had no antibacterial activity. The in vivo activity of topically administered
piritetrate against experimental dermal
infection of guinea pigs with T. mentagrophytes was more effective than that of
tolnaftate both mycologically and clinically.
Piritetrate manifested no acute toxicity in laboratory animals when administered even in large quantities by the oral, intraperitoneal, and topical routes.