Every medicine has some or the other side effect and so does Viagra. It depends on individual to individual and is usually mild to moderate and don’t last longer than a few hours. Mostly these side effects are evident with high intakes of Viagra. The most common side effects of Viagra are headache, nausea, flushing of the face, and upset stomach. Also there can be some temporary changes in color vision (such as trouble telling the difference between blue and green objects or having a blue color tinge to them), eyes becoming sensitive to light, or blurred vision.
But if you become dizzy or nauseated, or have pain, numbness, or tingling in your chest, arms, neck, or jaw during sexual activity, stop and call your doctor right away. You could be having a serious side effect of Viagra, or if you have sudden vision loss or have any of these signs of allergic reactions like hives; difficulty breathing; swelling of your face, lips, tongue, or throat seek emergency medical help immediately. It is also advisable to stop using Viagra and call your doctor immediately if you have any of these serious problems like - chest pain or heavy feeling, pain spreading to the arm or shoulder, nausea, sweating, general ill feeling; irregular heartbeat; swelling in your hands, ankles, or feet; shortness of breath and vision changes.
In rare instances, men have reported an erection that lasts many hours. But if this is the case then you should call a doctor immediately if an erection lasts more than 4 hours. If not treated right away, permanent damage to your penis could occur. Heart attack, stroke, irregular heartbeats, and death have been reported rarely in men taking Viagra. Most, but not all, of these men had heart problems before taking this medicine. It is not possible to determine whether these events were directly related to Viagra.