Unlike fluconazole, voriconazole has potent activity against a broad variety of fungi, including the clinically important pathogens. Several publications have substantiated the use of voriconazole against some of the newer and rarer fungal pathogens. Voriconazole is more potent than itraconazole against Aspergillus spp. and is comparable to posaconazole,50 another azole that is in clinical trials, in its activity against C. albicans. In general, Candida spp. that are less susceptible to fluconazole possess higher MICs to voriconazole. The in vitro activity of posaconazole appears to be similar to that of voriconazole. Posaconazole is now in phase III clinical trials, and evidence of the efficacy of posaconazole against various fungal models, especially the rarer ones, continues to accumulate. Posaconazole exhibits high oral bioavailability, but its low water solubility makes its formulation into an intravenous solution impossible.
A search for potential prodrug forms of posaconazole has yielded a possible candidate, SCH 59884. The compound is inactive in vitro but is dephosphorylated in vivo to yield the active 4-hydroxybutyrate ester. This compound is hy-drolyzed to the parent compound in the serum. Posaconazole undergoes extensive enterohepatic recycling, and most of the dose is eliminated in the bile and feces.
Syn2869 is a novel broad-spectrum compound that contains the piperazine-phenyl-triazolone side chain common to itraconazole and posaconazole, and it displays potency and an antifungal spectrum similar to those of the latter. Syn2869 demonstrates better activity than itraconazole in animal models of c. albicans, C. glabrata, and c. neoformans. The oral bioavailability (F) is 60%, and higher
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