Sildenafil Viagra is used to treat erectile dysfunction impotence; inability to get or keep an erection in men. To use the oral liquid: Shake the bottle well for at least 10 seconds before each use. This medicine usually begins to work for erectile dysfunction within 30 minutes after taking it. If you experience chest pain, dizziness, or nausea during sexual activity, call your doctor immediately and avoid sexual activity until your doctor tells you otherwise. Do not take a double dose to make up for a missed one. When taken at the correct time and paired with sexual stimulation, the erection lasts long enough for successful intercourse.According to price-comparison site test1.ru, generic Revatio will cost you as little as $ per pill, depending on where you fill your prescription. That’s compared with more than $50 per. Get the best deals for Viagra at test1.ru We have a great online selection at the lowest prices with Fast & Free shipping on many items! Typical dosing for Sildenafil (Viagra) The typical dose is to take 50 mg of sildenafil (Viagra) by mouth, about 1 hour before sex, as needed. The maximum recommended dose is mg. Don’t take sildenafil (Viagra) more than once daily (at any dose). Written by Brian Leonard, PharmD, BCACP, BCGP.