Kidney disease that needs to be treated with dialysis. Use only the brand of this medicine that your doctor prescribed. Make sure to get an estimate of when you can expect your prescription in the mail. Your primary care doctor should always know what medications you’re taking, including ED pills prescribed by another provider. Tell your doctor if sildenafil is not working well or if you are experiencing side effects. Alternatively, the medicine may be taken 30 minutes to 4 hours before sexual intercourse. · Print Save Sildenafil Generic name: sildenafil (oral) [ sil-DEN-a-fil ] Brand names: Revatio, Viagra Drug classes: Agents for pulmonary hypertension, Impotence . Best Low Cost: GoodRx Fastest Delivery: Blink Health: Sesame Sign Up Now Key Specs Cost: Consultation prices vary based on the prescriber; $5 generic . Why is this medication prescribed? Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men.