On January 4, 2016 FDA cautioned that differences in dosing regimens between the two oral formulations of the antifungal Noxafil (active ingredient posaconazole) have resulted in dosing errors. To help prevent additional medication errors, the drug labels were revised to indicate that the two oral formulations cannot be directly substituted for each other but require a change in dose. Direct milligram for milligram substitution of the two formulations can result in drug levels that are lower or higher than needed to effectively treat certain fungal infections.
Source: FDA Drug Safety Podcasts