When a man is sexually stimulated, his body’s normal response is to increase blood flow to his penis to produce an erection. This leads to more blood flow to the penis, leading to stronger erections. Here are some key factors to consider when deciding: Pricing: Know how much your monthly supply will cost with shipping and tax. If you are taking sildenafil for erectile dysfunction, your doctor will probably start you on an average dose of sildenafil and increase or decrease your dose depending on your response to the medication. Sildenafil treats PAH by relaxing the blood vessels in the lungs to allow blood to flow easily.Generic Name(S): sildenafil. Uses; Side Effects; before sexual activity (1 hour before is the most effective). Do not take more than once daily. Does Viagra interact with other drugs you. Take sildenafil at least 30 minutes, but no more than 4 hours, before sexual activity (1 hour before is the most effective). Do not take more than once daily. A high- fat meal may delay how.  · Teva sildenafil is a generic version of Viagra used to treat erectile dysfunction (ED) and some heart conditions. Additionally, research shows Teva sildenafil may be effective in treating both.