Without physical action to the penis, such as that occurring during sexual intercourse, sildenafil will not work to cause an erection. Take sildenafil as needed before sexual activity. Kidney disease that needs to be treated with dialysis. Often, these are prescribed for chest pain called angina. Sildenafil usually should not be taken more than once every 24 hours. If you experience chest pain, dizziness, or nausea during sex, seek immediate medical help.The typical dose is to take 50 mg of sildenafil (Viagra) by mouth, about 1 hour before sex, as needed. The maximum recommended dose is mg. Don’t take sildenafil (Viagra) . He or she will tell you how much VIAGRA to take and when to take it. Get into the mood. You will not get an erection just by taking VIAGRA. You must be sexually stimulated for it to work. Take your time. VIAGRA usually starts to work within minutes. You may take it up to 4 hours before sexual activity. Brand-name Viagra is also available through Optum Store in , , mg pills starting at $80 per dose if purchased in bulk. Pros & cons Free online consultation and free shipping on medications.