Sales of oseltamivir in Norway prior to the emergence of oseltamivir resistant influenza A(H1N1) viruses in 2007-08

Virol J. 2009 May 12;6:54. doi: 10.1186/1743-422X-6-54.

Abstract

Background: An unprecedented high proportion of oseltamivir resistant influenza A(H1N1) viruses emerged in the 2007-08 influenza season. In Norway, two thirds of all tested A(H1N1) viruses were resistant to the antiviral drug. In order to see if this emergence could be explained by a drug induced selection pressure, we analysed data on the sales of oseltamivir in Norway for the years 2002-07.

Methods: We used data from two sources; the Norwegian Drug Wholesales Statistics Database and the Norwegian Prescription Database (NorPD), for the years 2002-2007. We calculated courses sold of oseltamivir (Tamiflu) per 1000 inhabitants per year.

Results: Our data showed that, except for the years 2005 and 2006, sales of oseltamivir were low in Norway; courses sold per 1000 inhabitants varied between 0.17-1.64. The higher sales in 2005 and 2006 we believe were caused by private stockpiling in fear of a pandemic, and do not represent actual usage.

Conclusion: A drug induced selection pressure was probably not the cause of the emergence of oseltamivir resistant influenza A(H1N1) viruses in 2007-08 in Norway.

MeSH terms

  • Antiviral Agents / therapeutic use*
  • Commerce / statistics & numerical data*
  • Drug Resistance, Viral*
  • Humans
  • Influenza A Virus, H1N1 Subtype / drug effects*
  • Influenza A Virus, H1N1 Subtype / physiology
  • Influenza, Human / drug therapy*
  • Influenza, Human / virology
  • Norway
  • Oseltamivir / therapeutic use*

Substances

  • Antiviral Agents
  • Oseltamivir