title: Internet-ordered viagra (sildenafil citrate) is rarely genuine.
abstract: BACKGROUND
  Counterfeit medication is a growing problem. This study assessed the requirement for prescription, cost, origin, and content of medications sold via the Internet and purporting to be the phosphodiesterase type 5 inhibitor Viagra (sildenafil citrate).
  
  
  METHODS
  Pfizer monitored top search results for the query "buy Viagra" on the two leading Internet search engines in March 2011. Orders were placed from 22 unique Web sites claiming to sell Viagra manufactured by Pfizer. Tablets received were assessed for chemical composition.
  
  
  RESULTS
  No Web site examined required a prescription for purchase or a health screening survey; 90% offered illegal "generic Viagra." Cost per tablet ranged from $3.28-$33.00. Shipment origins of purchases were Hong Kong (N = 11), the United States (N = 6), and the United Kingdom (N = 2) as well as Canada, China, and India (N = 1 each). Notably, the four Internet pharmacies claiming to be Canadian did not ship medication from a Canadian address. Of 22 sample tablets examined, 17 (77%) were counterfeit, 4 (18%) were authentic, and 1 (5%) was an illegal generic. Counterfeit tablets were analyzed for sildenafil citrate, the active pharmaceutical ingredient (API) of Viagra, and contents varied between 30% and 50% of the label claim. Counterfeits lacked product information leaflets, including appropriate safety warnings, and genuine Viagra formulations.
  
  
  CONCLUSIONS
  Internet sites claiming to sell authentic Viagra shipped counterfeit medication 77% of the time; counterfeits usually came from non-U.S. addresses and had 30% to 50% of the labeled API claim. Caution is warranted when purchasing Viagra via the Internet.
authors.affiliation: Pfizer Inc, New York, NY, USA.
authors.forename: Neil
authors.initials: N
authors.lastname: Campbell
authors.forename: John P
authors.initials: JP
authors.lastname: Clark
authors.forename: Vera J
authors.initials: VJ
authors.lastname: Stecher
authors.forename: Irwin
authors.initials: I
authors.lastname: Goldstein
mesh_terms: D058110:Counterfeit Drugs / Q000009:adverse effects / Q000032:analysis*; D004348:Drug Labeling / Q000331:legislation & jurisprudence; D011307:Drug Prescriptions; D004335:Drug and Narcotic Control / Q000331:legislation & jurisprudence*; D016568:Drugs, Generic / Q000009:adverse effects* / Q000032:analysis*; D005607:Fraud / Q000331:legislation & jurisprudence*; D006801:Humans; D013287:Illicit Drugs / Q000009:adverse effects / Q000032:analysis*; D020407:Internet; D008297:Male; D058986:Phosphodiesterase 5 Inhibitors / Q000009:adverse effects / Q000032:analysis*; D010879:Piperazines / Q000009:adverse effects / Q000032:analysis*; D011687:Purines / Q000009:adverse effects / Q000032:analysis; D000068677:Sildenafil Citrate; D013450:Sulfones / Q000009:adverse effects / Q000032:analysis*
chemical_list: D058110:Counterfeit Drugs; D016568:Drugs, Generic; D013287:Illicit Drugs; D058986:Phosphodiesterase 5 Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D000068677:Sildenafil Citrate