Sildenafil may cause side effects. Do not take a double dose to make up for a missed one. Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual stimulation. Do not mix the liquid with other medications or add anything to flavor the medication. However, if you take sildenafil with a high-fat meal, it will take longer for the medication to start to work. Talk to your doctor about eating grapefruit and drinking grapefruit juice while taking this medicine.The recommended dosage of Viagra for erectile dysfunction (ED) is 50 mg, taken as needed about 1 hour before sexual activity. You can take it 30 minutes to 4 hours before sexual activity. And you. Sildenafil price As with all medications, the cost of sildenafil can vary. Factors that may affect the price you’ll pay include your treatment plan, your insurance coverage, the form . According to price-comparison site test1.ru, generic Revatio will cost you as little as $ per pill, depending on where you fill your prescription. That’s compared with .