Viagra is also informally known as “vitamin V”, “the blue pill”, or “blue diamond”, as well as various other nicknames. How should this medicine be used? Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient. Kidney disease, severe or Liver disease, severe—Use with caution. However, the dose is usually not more than 80 mg 3 times a day. This includes prescription or nonprescription over-the-counter [OTC] medicines and herbal or vitamin supplements.Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. Sildenafil (Liqrev, Revatio) is used to improve the ability to exercise in adults (Liqrev, Revatio) and children 1 year of age and older (Revatio) with pulmonary arterial hypertension (PAH; high blood pressure in the vessels carrying blood to the . AdEnjoy Greater Libido & Performance. Fast Express Shipping. Viagra (sildenafil) is a prescription drug that’s used to treat erectile dysfunction (ED). The drug comes as a tablet you’ll take by swallowing. It’s usually taken as needed about 1 hour.