Side effects of Viagra include headache, heartburn, diarrhoea, nosebleeds, numbness, burning, tingling in the arms, hands, feet, or legs and muscle aches. More serious side effects include sudden loss of vision, blurred vision, sudden decrease or loss of hearing, erection that is painful or lasts longer than 4 hours, dizziness, fainting, chest pain, itching or burning during urination and genital rash. Seek urgent medical assistance if any of these symptoms are severe or do not go away.
Attribution: Straight Talk Foundation