What are the concerns regarding use of viagra (sildenafil)?

Priapism/cardiovasc. Main concerns are priapism, which is n erection lasting >4hours. Needs to be treated promptly to avoid permanent erectile dysfunction. Of concern if subject has significant arteriosclerosis putting him at risk for stroke + stroke-like symptoms of loss of vision, hearing and severe headaches. Severe allergic can also occur after repeated usage. Fortunately severe side-effects or problems are rare.
Concerns. The main side effects with any pde-5 inhibitor (viagra, levitra, (vardenafil) cialis) include possible sudden drops in blood pressure, sinus congestion and/or headaches from vasodilation, and prolonged erection (priapism). Also, you need to review your entire medication list with the doctor, some medications make it dangerous to take along with a pde-5 inhibitor.
Cardiac history. If you take medicine like nitro for chest pain viagra (sildenafil) can cause an unsafe drop in blood pressure or even death. I encourage pts with a cardiac history to be cleared by their cardiologist before using viagra (sildenafil). Also so other medications can't be used with viagra (sildenafil), so a good drug interaction check is important.