Do NOT take if you: don't have any erection problem, take any nitrate medicine for chest pain or heart failure, take riociguat (or other guanylate cyclase stimulators) for high blood pressure in the lungs, take ritonavir for the treatment of HIV, have been advised by your doctor to avoid sexual activity because of a problem with your heart or blood vessels, have a severe heart or liver problem, have low blood pressure, have ever had severe vision loss or a rare inherited eye disorder, have a deformed penis, have an allergy to any of the ingredients in this product.