If you see air bubbles in the syringe, repeat the steps. Sildenafil does not prevent pregnancy or the spread of sexually transmitted diseases such as human immunodeficiency virus HIV. How should this medicine be used? Storage Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine. Brand names Why is this medication prescribed? Your doctor may need to change the doses of your medications or monitor you carefully for side effects.Brand: Viagra. Form: oral tablet; Strengths: 25 mg, 50 mg, mg; Adult dosage (ages 18–64 years) Typical dosage: 50 mg, taken as needed about 1 hour before sexual activity. It can be taken Viagra can decrease blood flow to the optic nerve of the eye, causing sudden vision loss. This has occurred in a small number of people taking sildenafil, most of whom also had heart disease, diabetes, high blood pressure, high cholesterol, or certain pre-existing eye problems, and in those who smoked or were over 50 years old. Sildenafil Citrate Coupons, Prices, and Savings Card. Brand Names: Revatio, Viagra. Sildenafil is used to treat male sexual function problems (impotence or erectile .