This information is reviewed by a licensed practitioner who will assess your eligibility for the medication. Insurance: If you plan to use insurance, make sure the online provider accepts it. The combination can cause a dangerous fall in your blood pressure. Sildenafil may cause side effects. About sildenafil Viagra Sildenafil is a medicine used to treat erection problems erectile dysfunction.If you buy sildenafil for erectile dysfunction, it can also be known by the brand names Viagra, Aronix, Liberize and Nipatra. Sildenafil for pulmonary hypertension can also be known by the brand names Revatio and Grandipam. This medicine is available on prescription and you can also buy it from most pharmacies. Rarely reported side effects include: an erection that will not go away (priapism). If you have an erection that lasts more than 4 hours, get medical help right away. If it is not treated right away, priapism can permanently damage your penis. sudden vision loss in one or both eyes. Depending on your symptoms and needs, you may be prescribed Viagra, sildenafil, Cialis, tadalafil, Stendra, paroxetine, or a combination of tadalafil and sildenafil, available as mints or pills. Prices range from $3 to $ per dose or $82 to $ for a monthly supply, depending on the medication.