Sildenafil treats PAH by relaxing the blood vessels in the lungs to allow blood to flow easily. You should only be treated with one of these products at a time. All PDE5 inhibitors, including Viagra and Cialis, require a valid prescription regardless of the pharmacy or provider. An inherited eye disease that affects the retina. If you are taking sildenafil to treat erectile dysfunction, follow your doctor’s directions and the guidelines in this paragraph. Those with pre-existing conditions should always consult a healthcare provider before taking new medications or supplements.Roman’s consultations and follow-ups are free. Medication prices vary based on what your prescriber recommends, whether it’s a generic version, and how many pills you order per shipment. Generic Viagra (sildenafil): $4 per 25 mg pill, $6 per 50 mg pill, $10 per mg pill; Branded Viagra: $90 per 25 mg, 50 mg, or mg pill. Oral medicines for ED usually work well and cause few side effects. The four main medicines taken by mouth for erectile dysfunction are: Avanafil (Stendra). Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. 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 oral suspension (liquid), and an.