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


CONCLUSIONS
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.
Hauge
Siri H
SH
Department of Infectious Disease Epidemiology, Norwegian Institute of Public Health, Oslo, Norway. siri.helene.hauge@fhi.no
Blix
Hege S
HS
Borgen
Katrine
K
Hungnes
Olav
O
Dudman
Susanne G
SG
Aavitsland
Preben
P
D000998:Antiviral Agents / Q000627:therapeutic use*; D003132:Commerce / Q000706:statistics & numerical data*; D024882:Drug Resistance, Viral; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000187:drug effects* / Q000502:physiology; D007251:Influenza, Human / Q000188:drug therapy* / Q000821:virology; D009664:Norway; D053139:Oseltamivir / Q000627:therapeutic use*
D000998:Antiviral Agents; D053139:Oseltamivir