Some people may also have ringing in their ears tinnitus or dizziness. The most common side effects of VIAGRA: headache; flushing; upset stomach; abnormal vision, such as changes in color vision such as having a blue color tinge and blurred vision; stuffy or runny nose; back pain; muscle pain; nausea; dizziness; rash. Proper Use Use sildenafil exactly as directed by your doctor. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to take it. PDE5Is reduce systemic and pulmonary arterial pressures and cardiac output thereby having vasodilator effects to increase blood flow to the penis to help a man get and keep an erection.Sildenafil is a medication used in the management and treatment of erectile dysfunction and pulmonary arterial hypertension. It is in the phosphodiesterase-5 inhibitor (PDE5-I) class of medications. This activity describes the indications, actions, adverse effects, and contraindications of sildenafil as an agent in the clinical setting. Knowledge . Sildenafil is used to treat erectile dysfunction (ED) and to reduce blood pressure in pulmonary arterial hypertension (PAH). It is taken when needed for ED and daily for PAH. A headache, stomach upsets, and flushing are the main side effects, and it should not be taken within 24 hours of a nitrate. 5. Tips. The Savings Offer and Program expire on 12/31/ For further information, call , visit test1.ru, or write: Viatris Inc., P.O. Box , Mission, KS See risks & benefits. Learn more about what VIAGRA® (sildenafil citrate), a prescription treatment for ED.