Viagra, normally marketed under several trade names, is now being used to treat pulmonary hypertension because it boosts the levels of nitric oxide in the body. Nitric oxide is a vasodilator, which means it can lower blood pressure, especially when used alongside other similar blood pressure-lowering drugs such as nitrates — nitroglycerine and isosorbide.
However, I would reason that Viagra and other blood pressure-lowering drugs might act in an additive or synergistic way to influence the blood pressure. Thus, ensure that your physician is aware of other medications you’re on before you take Viagra.