You could also ask your pharmacist for advice on other ways to help you remember to take your medicine. You need to be sexually excited for it to work. If you are taking sildenafil to treat erectile dysfunction, follow your doctor’s directions and the guidelines in this paragraph. Shake the liquid well for 10 seconds before each use to mix the medication evenly. Most erectile dysfunction medications belong to the drug class known as PDE5 inhibitors , which help relax the muscles and increase blood flow to allow for a full erection. It’s available in 25 mg, 50 mg, and mg tablets and lasts up to 18 hours.Take it on an empty stomach, with no food at least 2 hours it with glass water to make sure it reaches your efficacy is life of viagra is . There is generic Viagra now. They have 20mg and mg tablets. It’s usually $/bottle depending on your pharmacy. 2. ClandestineUs. • 5 yr. ago. Wow! What’s the name? 2. Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. Sildenafil (Liqrev, Revatio) is used to improve the ability to exercise in adults (Liqrev, Revatio) and children 1 year of age and older (Revatio) with pulmonary arterial hypertension (PAH; high blood pressure in the vessels carrying blood to the .