title: Study links viagra to infertility.
mesh_terms: D000328:Adult; D002243:Carbolines / Q000009:adverse effects / Q000627:therapeutic use; D007172:Erectile Dysfunction / Q000139:chemically induced* / Q000188:drug therapy; D005298:Fertility / Q000187:drug effects*; D006801:Humans; D008297:Male; D010879:Piperazines / Q000009:adverse effects* / Q000627:therapeutic use; D011687:Purines / Q000009:adverse effects* / Q000627:therapeutic use; D013084:Sperm-Ovum Interactions / Q000187:drug effects*; D013094:Spermatozoa / Q000187:drug effects*; D013450:Sulfones / Q000009:adverse effects* / Q000627:therapeutic use
chemical_list: D002243:Carbolines; D010879:Piperazines; D011687:Purines; D013450:Sulfones