Sexual activity may be a strain on your heart, especially if you have heart disease. When hypertension occurs in the lungs, the heart must work harder to pump enough blood through the lungs. Proper Use Use sildenafil exactly as directed by your doctor. The following information includes only the average doses of this medicine. If you ever need emergency medical treatment for a heart problem, the healthcare providers who treat you will need to know when you last took sildenafil.For daily use, Goldstein said, the generic form, sildenafil, comes in mg tablets. “We prescribe one mg tablet a night, a classic dose,” he said. “Should they wish to have sex, they. Cut a higher-dosage pill in half to save 50% or more. How much does Sildenafil cost? expand_more. The lowest GoodRx price for the most common version of Sildenafil is around $, 95% off the average retail price of $ Read more about Sildenafil. See more about Erectile Dysfunction.  · Adults up to 65 years of age—50 milligrams (mg) as a single dose no more than once a day, 1 hour before sexual intercourse. Alternatively, the medicine may be taken 30 minutes to 4 hours before sexual intercourse. (Cialis®) or vardenafil (Levitra®). Viagra® also contains sildenafil. If you take too much sildenafil or take it together.