Treatment of Experimental Murine Cryptococcosis: a Comparison of Miconazole and Amphotericin B

Miconazole was compared with amphotericin B in the treatment of murine cryptococcosis. Both subcutaneous and intraperitoneal administration of miconazole produced serum levels higher than the minimum inhibitory concentration for the challenge strain. However, maximal tolerable doses of miconazole gave no increase in survival. When combined with amphotericin B, miconazole demonstrated neither additive nor antagonistic effects on survival. Spleen and brain counts of cryptococci were not lowered by miconazole; also, miconazole did not alter the effect of amphotericin B on reducing tissue counts. In vitro studies confirmed that the strain of Cryptococcus neoformans was quite susceptible to both miconazole and amphotericin B. However, miconazole had a delayed onset of antifungal activity. This was apparent even at miconazole levels 20 times greater than the minimum inhibitory concentration. Also, the antifungal activity of miconazole was markedly inhibited by serum. Delayed antifungal activity and serum inhibition may limit the in vivo effectiveness of miconazole in murine cryptococcosis.