Vardenafil usually works for 4 to 5 hours. Sildenafil Viagra is used to treat erectile dysfunction impotence; inability to get or keep an erection in men. If you are taking sildenafil for PAH, take the missed dose as soon as you remember it. Shake the liquid well for 10 seconds before each use to mix the medication evenly. 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. As with sildenafil, a high-fat meal or alcohol keep the body from absorbing it as quickly.Best subscription service for Viagra and generic Viagra: Rex MD Viagra Although erectile dysfunction (ED) may be an upsetting diagnosis for some, many people find their . According to price-comparison site , 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. Teva’s version of sildenafil debuted at an average cash price of around $30 per pill, roughly 50% cheaper than brand-name Viagra. Since then, more manufacturers have brought .