Your doctor or other health care professional can recommend one for you based on these factors, other health conditions you have and any other medicines you take. This patent was published in and expired in Vardenafil usually works for 4 to 5 hours. However, if you take sildenafil with a high-fat meal, it will take longer for the medication to start to work. A newer form of the medicine that dissolves on the tongue might work faster than the pill that you swallow. When oral medications might not be safe Check with your health care team before you take any medicine for erectile dysfunction. These small differences affect the way each medication works, such as how quickly it takes effect and wears off, and the possible side effects.The active drug in Viagra is sildenafil. It belongs to a group of drugs called phosphodiesterase-5 inhibitors. If you’ve had an allergic reaction to Viagra or any of . Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes . 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 .