You may opt-out of email communications at any time by clicking on the unsubscribe link in the e-mail. You should only be treated with one of these products at a time. Sildenafil comes as a tablet and suspension liquid to take by mouth. Do not take more or less of it or take it more often than prescribed by your doctor. If you are taking sildenafil for PAH, take the missed dose as soon as you remember it.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 (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. 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 .