Premedication for IV Contrast Allergy Make an Appointment Ask a Question Refer Patient Your health care provider has scheduled you for a procedure at National Jewish Health that requires intravenous (IV) contrast. The contrast will be given as an injection in a vein using an IV. Since you are at risk for having an allergic response to the contrast, your health care provider has ordered the medications listed below. You need to take these before the procedure to reduce the risk of an allergic response. The prednisone tablets require a prescription. The diphenhydramine (Benadryl® common brand) is available over the counter. These medications are available as a convenient kit from the National Jewish Health pharmacy. If you do not want to use the National Jewish Health pharmacy, ask your health care provider to send a prescription for prednisone to a pharmacy of your choice. We suggest you write down the date and time of your procedure to remind yourself when you need to take the medications. 12 hours prior to your procedure take: Prednisone 32 mg. by mouth 2 hours prior to your test take: Prednisone 32 mg. by mouth 1 hour prior to your test take: Benadryl 50 mg. by mouth If you have questions, please contact your health care team via the patient portal or by calling 303.398.1355 Option 4 or 1.800.222.5864.