Concerning the arousal response, decreased testosterone blood levels can influence the efficacy of sildenafil Viagra. What you can do Take these steps to prepare for your appointment: Ask what you need to do ahead of time. British Journal of Ophthalmology, 90 2 , — Some of the symptoms of an allergic reaction may include skin rash, itching, or difficulty breathing. Swallow one tablet with a glass of water. Some of Levitra’s most common side effects include: Flushing.Viagra and Levitra take about 30 minutes to work, and the effects last for about 4 hours after you take the pill. You should take Cialis at least 2 hours before you plan to have sex. The effects. Levitra may interact with nitrate drugs for chest pain or heart problems, other medications for erectile dysfunction, conivaptan, diclofenac, imatinib, isoniazid, antidepressants, antibiotics, antifungals, drugs to treat high blood pressure or a prostate disorder, heart or blood pressure medications, heart rhythm medicine, or HIV/AIDS . Vardenafil 4 tablets Blister 20 mg. Vardenafil, sold under the brand name Levitra among others, is a medication that is used for treating erectile dysfunction. [1] [2] It is a PDE5 inhibitor. [1] It is taken by mouth.