title: Generic versions launched as  Viagra® goes off-patent.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Sklan
mesh_terms: D016568:Drugs, Generic; D007172:Erectile Dysfunction / Q000188:drug therapy; D005060:Europe; D006801:Humans; D008297:Male; D010879:Piperazines; D011687:Purines; D000068677:Sildenafil Citrate; D013450:Sulfones
chemical_list: D016568:Drugs, Generic; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D000068677:Sildenafil Citrate