Oseltamivir (Tamiflu) resistant H1N1 swine flu emerging

Oseltamivir or Tamiflu-resistant swineflu causing H1N1 influenza A virus is emerging across the world, though only restricted to certain isolated pockets, reports suggest.

Oseltamivir (Tamiflu) is one of the few options currently available to treat the pandemic H1N1 strain of the virus.

There have been 13 cases of pandemic swine flu becoming resistant to oseltamivir (Tamiflu), reported around the world, according to the maker of the drug Roche of Switzerland.

Oseltamivir-resistance is very low in percentage and the resistant strain of H1n1 has not passed the on to other people, Roche sources maintained.

Tamiflu, whose generic name is oseltamivir, is one of two main antivirals in the arsenal against swine flu as the world awaits the widespread availability of a vaccine against the disease.

Roche’s sstudies concluded that 0.32 percent of adults and 4 percent of children who took oseltamivir (Tamiflu) developed resistance.

The 13 cases were scattered around the world in Europe, the United States and Asia.

The oseltamivir resistant variety also produces only mild symptoms as it is typical widespread version of the H1n1 virus.

Roche was not quite certain why the 13 patients developed the resistance while taking the drug. Possibly, patients who were taking inadequate doses – only half a dose – of the prescribed dosage of the drug were developing oseltamivir resistance, Roche said.

“If they were actually infected with the virus, the dosage of the drug may have been too low,” Roche sources were quoted as saying in media reports.

The Tamiflu supplier was also taking a closer view on H1n1 virus’ interaction with oseltamivir.

Oseltamivir can be taken as a preventive at the half-dose strength if taken for up to six weeks.

But in case of the patients presenting with symptoms, medical practitioners should prescribe the full treatment dose and not the prevention dose which half-doze strength.

Denmark, Japan, Hong Kong, Canada & Thailand are among the nations that reported cases of oseltamivir-rasistant strains of H1N1 virus.

Among the Asian countries, Japan has confirmed two cases of A/H1N1 resistance to oseltamivir (Tamiflu).

Thailand, China, Singapore reportrd atleast one case of oseltamivir resistance.
In Hong Kong, Tamiflu-resistant swine flu was found in a teenager who did not take Tamiflu.

Influenza virus shares similar features as HIV-1 including high replication rates in many hosts, and the generation of large numbers of viral mutants. The difference with influenza is that a vaccine is available.

However, antiviral compounds like osetamivir (Tamiflu) and Zanamavir (Relenza) – an alternative inhalable anti-viral from GlaxoSmithKline–should only be used with caution, experts alert.