Your doctor may adjust your dose as needed and tolerated. If you experience a prolonged or painful erection for 4 hours or more, contact your doctor immediately. Shake the liquid well for 10 seconds before each use to mix the medication evenly. Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual stimulation. Often, these are prescribed for chest pain called angina. When oral medications might not be safe Check with your health care team before you take any medicine for erectile dysfunction. · The highest recommended Viagra dose for treating erectile dysfunction (ED) is mg per day, according to the drug’s manufacturer. Doses of mg or mg would be considered off-label g: mmc. 1. Avoid taking Viagra with a large meal or high-fat meal. Viagra blood levels peak an hour after you swallow the tablet on an empty stomach. According to Ramin, if you eat a large or high-fat. Viagra (sildenafil) is a brand-name oral tablet prescribed for erectile dysfunction. The cost of the drug with and without insurance can depend on several factors, such as whether Viagra has a Missing: mmc.