Medication Monitor



Generic Name (Trade Name—Company)
Notes
January 4, 2016

Posaconazole

(Noxafil—Merck)
Dosing errors may occur when switching between different oral formulations of antifungal med

FDA is cautioning that differences in dosing regimens between the two oral formulations—an oral suspension and a delayed-release tablet—of the antifungal 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 mg for mg substitution of the two formulations can result in drug levels that are lower or higher than needed to effectively treat certain fungal infections.

Posaconazole is used to help prevent certain invasive fungal infections caused by Aspergillus and Candida. It is used in patients who have an increased chance of getting these infections because of weakened immune systems. The oral suspension formulation is also used to treat thrush caused by Candida in the mouth or throat area.

Prescribers should specify the dosage form, strength, and frequency on all prescriptions they write for posaconazole. Pharmacists should request clarification from prescribers when the dosage form, strength, or frequency is not specified. Patients should talk to their health professional before they switch from one oral formulation to the other.

Posaconazole was approved in 2006 as an oral suspension formulation. Since the approval of posaconazole delayed-release tablets in November 2013, FDA received 11 reports of the wrong oral formulations being prescribed and/or dispensed to patients. One case resulted in death, and an additional case resulted in hospitalization. According to the reports, these outcomes were a result of health professionals not knowing that the two oral formulations cannot be substituted for each other without adjusting the dose due to differences in how the medicine is absorbed and handled by the body. Posaconazole is also approved as an I.V. solution for injection. 

In addition to changes to the outer carton of posaconazole (see photos), its manufacturer revised the prescribing information and the patient information in the drug label to alert patients and their health professionals that the two oral formulations cannot be substituted for each other.