Sildenafil Viagra. Tadalafil Cialis. Talk to your doctor about eating grapefruit and drinking grapefruit juice while taking this medicine. What should I do if I forget a dose? How oral medicines differ Each oral medicine for ED has a slightly different chemical makeup. Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient.This is a generic drug. The average cost for 30 Tablet(s), mg each of the generic (sildenafil citrate) is $ You can buy sildenafil citrate at the discounted price of . 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. 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.