The commonest Unwanted effects of VIAGRA: headache; flushing; upset abdomen; abnormal eyesight, like variations in colour eyesight (like having a blue color tinge) and blurred vision; stuffy or runny nose; back suffering; muscle discomfort; nausea; dizziness; rash.Hemic and Lymphatic: vaso-occlusive disaster: In a little, prematurely terminated stu