Instructions for Viagra, Cialis, etc. say not to take w/ BP meds. I'm thinking there are a cpl possibilities. Diovan (Valsartan) is available in different doses (20 mg, 40 mg, etc.), so maybe you could take a lower dose on the day you'll be using Viagra. Or possibly just skip your usual dose that day, then resume the next. However, your Dr. may not agree. I think the best strategy is to ask your Dr. about using these 2 drugs at the same time.