Viagra comes as a tablet containing sildenafil citrate, to take by mouth. For most men, the recommended dose is 50 mg. taken, as needed, approximately 1 hour before sexual activity. However, sildenafil citrate may be taken anywhere from 4 hours to 0.5 hour before sexual activity. Based on effectiveness and toleration, the dose may be increased to a maximum recommended dose of 100 mg or decreased to 25 mg. The maximum re