This can happen if you are sick with fever, diarrhea, or vomiting; sweat a lot; or do not drink enough liquids. Sildenafil comes as a tablet and suspension liquid to take by mouth. This will increase the supply of blood to the lungs and reduce the workload of the heart. Tell your doctor if any of these symptoms are severe or do not go away: headache. This product is available in the following dosage forms: Tablet Suspension There is a problem with information submitted for this request.Sildenafil oral tablet is available as a brand-name drug and as a generic drug. Brand names: Viagra, Revatio. Sildenafil comes in three forms: an oral tablet, an . Sildenafil is in a class of medications called phosphodiesterase (PDE) inhibitors. Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual .  · Sildenafil is used to treat men who have erectile dysfunction (also called sexual impotence). Sildenafil belongs to a group of medicines called phosphodiesterase .