Cialis Tadalafil is a tablet that does the same job but works for up to 36 hours, Stendra Avanafil has a faster average response time of 15 minutes, and Levitra Vardenafil is a more potent drug and is thought to be less likely to cause side effects. Answer: Viagra is generally thought to be low risk. 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. The products discussed in this site may have different product labeling in different countries. Some men are okay with these side effects, and find signs like facial flushing reassuring because it helps them to know the drug is working. So make sure you read the leaflet. Can women take Viagra? · a light-headed feeling, like you might pass out. Common sildenafil side effects may include: flushing (warmth, redness, or tingly feeling); headache, dizziness; . Viagra (sildenafil) is a brand-name oral tablet prescribed for erectile dysfunction. The cost of the drug with and without insurance can depend on several . Sildenafil Prices, Coupons and Patient Assistance Programs. Sildenafil is a member of the agents for pulmonary hypertension drug class and is commonly used for Erectile Missing: usa.