Viagra is a PDE-5 inhibitor approved by the FDA to treat erectile dysfunction (ED). It's the brand name of the specific drug made by Pfizer, who's active chemical in the medicine is sildenafil citrate. Viagra was initially created in 1989 by Pfizer and used to treat high blood pressure. Though not found to be helpful for the treatment of high blood pressure, this medication became available as an ED treatment in 1998 and has been commonly prescribed ever since. In 2017, generic sildenafil became available at a much lower cost than the brand-name medication.