Some medications should not be taken with sildenafil. Oral ED medicines might not work or might be dangerous if you also take any of the following: Nitrate medicines. Do not mix the liquid with other medications or add anything to flavor the medication. Especially tell your healthcare provider if you take any of the following: medicines called nitrates medicines called guanylate cyclase stimulators such as Adempas riociguat medicines called alpha-blockers, such as Hytrin terazosin HCl , Flomax tamsulosin HCl , Cardura doxazosin mesylate , Minipress prazosin HCl , Uroxatral alfuzosin HCl , Jalyn dutasteride and tamsulosin HCl , or Rapaflo silodosin. This development was credited largely “due to the introduction of generic products. The following nonprescription or herbal products may interact with sildenafil: cimetidine Tagamet HB , St. Tell your doctor if any of these symptoms are severe or do not go away: headache.Sildenafil (Viagra, Revatio) is a moderately priced drug used to treat erection problems in men. It is also used to treat pulmonary arterial hypertension, a serious heart and lung drug is more popular than comparable drugs. It is available in generic and brand versions. Generic sildenafil is covered by most Medicare and insurance plans, but . Why is this medication prescribed? Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. Viagra is an effective drug for treating male erectile dysfunction, but it targets sexual performance, not sexual arousal. There is limited evidence that Viagra may be beneficial for women with sexual dysfunction, but the .