Using fexofenadine with other drugs that make you drowsy can worsen this effect. Ask your doctor before using opioid medication, a sleeping pill, a muscle relaxer, or medicine for anxiety or seizures.
Ask a doctor or pharmacist before using fexofenadine with any other medications, especially:
ketoconazole; or
erythromycin.
This list is not complete. Other drugs may affect fexofenadine, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.
 Fexofenadine drug interactions (more detail)
