Kidney disease that needs to be treated with dialysis. Dosing is as follows: As needed for ED: 5 to 20 mg by mouth as a one-time dose, with a maximum of one dose in 24 hours. Pfizer Canada Inc. Effects may last up to 36 hours. Viagra vs. Oral medicine for ED also might not be safe or work well if you have: Very low blood pressure, called hypotension, or uncontrolled high blood pressure, called hypertension.Cialis is Food and Drug Administration (FDA) approved to treat erectile dysfunction (ED) and benign prostatic hyperplasia (BHP). Generic tadalafil became more widely available after We have good news for you: generic Cialis, used to treat erectile dysfunction (ED)and enlarged prostates, just hit pharmacies. Prices for the generic, known as tadalafil, are more than 50% less than those of brand-name Cialis. As more men are able to afford tadalafil and treat their ED, it’s likely that many will have questions. Sildenafil, sold under the brand name Viagra, among others, is a medication used to treat erectile dysfunction and pulmonary arterial hypertension. [4] [8] It is also sometimes used off-label for the treatment of certain symptoms in secondary Raynaud’s phenomenon. [9] It is unclear if it is effective for treating sexual dysfunction in females. [8].