<p>Posaconazole blocks the synthesis of ergosterol, a key component of the fungal cell membrane. It inhibits the cytochrome P-450 dependent enzyme Lanosterol 14-&alpha;-demethylase responsible for the conversion of lanosterol to ergosterol in the fungal cell membrane. This results in an accumulation of methylated sterol precursors and a depletion of ergosterol within the cell membrane, thus weakening the structure and function of the fungal cell membrane.</p>