No, you usually do not need to stop taking your blood pressure medicines when taking Viagra. It is generally safe to take Viagra with most blood pressure medicines. To be sure, talk to your doctor before you take Viagra with blood pressure medicines.

Some people’s blood pressure will go even lower when taking Viagra with some blood pressure medicines like amlodipine or alpha blockers, like doxazosin. Combining these medicines with Viagra may cause your blood pressure to go down more. However, this additional decrease is usually not dangerous.

You should not take Viagra with medicines called nitrates. Nitrates are usually not used for treating high blood pressure alone. They are used to treat heart failure or chest pain in people with heart disease. Combining Viagra with nitrates may cause dangerously low blood pressure. Before taking Viagra, check to be sure you are not taking a nitrate medicine. Common names of nitrate medicines include Nitrostat, NitroMist, Imdur, and Nitro-Bid.

Be careful if you're on nitrates, because you just might faint!