Viagra generally refers to sildenafil citrate, topical sildenafil has not been reported, but there is a medication that can be used externally to treat erectile dysfunction as prostaglandin E1 cream, which is used as directed by your doctor. Prostaglandin E1 cream is suitable for men with erectile dysfunction and is usually used 5-20 minutes before sexual intercourse. Before using the medication, urinate and wash your hands and genitals with soapy water. Remove the administration tube and take off the small cap. Gently press the glans with the index and thumb of the left hand to open the urethral opening. Gently insert the nozzle of the administration tube into the front of the urethral opening and squeeze the cream from the tube into the urethra, holding the penis upward in your hand for about 30 seconds so that the cream disappears in the urethral opening. Some patients with occasional local redness, swelling, glans, urethra pain when using the drug, stopping the drug after the natural disappearance. The above drugs are used in accordance with medical advice, if impotence and so on, it is recommended to go to the hospital as soon as possible, do not blindly use drugs to avoid adverse symptoms.