If you experience a prolonged or painful erection for 4 hours or more, contact your doctor immediately. Check with your doctor immediately if any of the following side effects occur: Less common burning feeling in the chest or stomach burning, crawling, itching, numbness, prickling, “pins and needles”, or tingling feelings cloudy or bloody urine. Slowly pull back the plunger until the required dose. This condition may require prompt medical treatment to prevent serious and permanent damage to your penis. Adults 65 years of age and older—25 mg as a single dose no more than once a day, 1 hour before sexual intercourse. Some illegal “street” drugs called “poppers” such as amyl nitrate, butyl nitrate, or nitrite. If you take too much Taking too much sildenafil can cause unpleasant side effects.The usual dose is 50mg, when you need it. Do not take it more than once a day. The dose can be increased to mg or decreased to 25mg depending on its effect. Take . Viagra is available in three strengths: 25 milligrams (mg), 50 mg, and mg. There is also a generic version of Viagra available, under the name sildenafil, in 25mg, 50mg, and mg strengths. 3. Downsides If you are between the ages of 18 and 60, .