Its effects might last longer if you have mild to moderate ED. Take sildenafil at around the same times every day. Shake the liquid well for 10 seconds before each use to mix the medication evenly. These small differences affect the way each medication works, such as how quickly it takes effect and wears off, and the possible side effects. As with sildenafil, a high-fat meal or alcohol keep the body from absorbing it as quickly. Talk to your doctor about eating grapefruit and drinking grapefruit juice while taking this medicine.Sildenafil, sold under the brand name Viagra, among others, is a medication used to treat erectile dysfunction and pulmonary arterial hypertension. [4] [8] It is also sometimes used . Drug Images What is Viagra? If you have erectile dysfunction (ED), your doctor may recommend that you take Viagra. It’s a prescription drug that’s used in adult males* with . Sildenafil (Viagra). This medicine works best when you take it on an empty stomach an hour before sex. The body takes longer to absorb it after a high-fat meal or alcohol. Its effects .