Tamiflu (oseltamivir) and Relenza (zanamivir) are the two drugs prescribed to treat swine flu caused by the H1N1 virus. But India has access only to Tamiflu (oseltamivir), though the mode of action for both the drugs is to block the viral receptors infecting the healthy cells.
The H1N1 virus is resistant to the drugs like amantadine, rimantadine, and other adamantanes. Both oseltamivir and zanamivir approved in 1999 by US FDA belong to a new class of neuraminidase inhibitors which are antiviral drugs to control influenza A and B viruses. The two drugs have gone through extensive clinical trials involving over 1,000 patients. Tamiflu has been successful to treat H5N1 virus (Avian Flu), is now responding positively to control H1N1 virus.
Even though Tamiflu is reporting adverse drug reactions like any other anti viral drug where nausea and vomiting are the most common side effects and less common reactions like delirium and hallucination, the drug has been extremely effective in treating scores of swine flu cases in the country, stated Dr Purnima Parthasarathy, head, (infectious diseases), Manipal Hospital.
Now the biggest challenge before medical experts in the country is to prevent drug resistance to Tamiflu in India, she added.
According to Professor PV Subba Rao, president, R&D, Bigtec Labs, the Tamiflu supplies made through the government makes a lot of sense. This will prevent the indiscriminate purchase of the drug by patients and reduce the risk of drug resistance which could make the condition go out of control.
"In fact, Tamiflu is not advisable even as a prophylactic because chances of drug resistance will be higher. Also it is well documented that Tamiflu could cause severe side effects, some of which are serious. Since H1N1 is a typical flu virus, those with higher immunity levels will not get the disease. The public should access the authorized swine flu centres for diagnosis and treatment which can help treat the flu right and prevent resistance to medication," said professor Rao.
Although the fatal cases reported in India from swine flu are due to related conditions like diabetes, cardiovascular conditions and respiratory diseases, medical experts have not yet come across any contra-indications with Tami Flu like in the case of rifampicin which is a bacteriostatic antibiotic drug for treatment of TB. However indiscriminate prescription of Tamiflu should be avoided to prevent drug resistance which could lead to a catastrophe. We are prescribing Tamiflu once-a-day to patients whom we are almost confirmed to be test positive of H1N1 virus before the reports are available, said Dr Shashidar Buggi, director, Rajiv Gandhi Institute of Chest Diseases.
As swine flu is going through its phase in the country, there is no reason to believe that the H1N1 virus strain is different here. This is a new virus to which humans have never been exposed reporting moderate to mild symptoms with recovery which is uneventful, said Dr Parthasarathy.
Since no one is able to predict how long the virus is going to be around, it is prudent to have more number of testing centres for early and quick diagnosis. Right now the National Institute Virology, Pune and NIMHANS are swarmed with samples which are sent to these labs using viral transport medium. It is evident that the logistics are becoming difficult to handle. On a war footing, the government must approve more certified labs to test H1N1 virus, said Dr Parthasarathy.