Tamiflu, the anti-influenza neuraminidase inhibitor, discovered by Gilead and marketed by Roche has been taking a beating lately. In Japan over 1000 adverse events have been reported in the less than 6 years since the time it became available. The interesting thing is that 128 of these reports suggest some type of CNS toxicity mainly involving apparent highly reckless behaviour…attempting to jump off buildings or running in front of moving cars.
In addition, Tamiflu-resistant virus is popping up, even in people who have never taken the drug. At this point it doesn’t appear to be a problem, since most people can handle the flu, regardless of its resistance profile to this drug. The real danger would be if this scenario repeats itself during an outbreak of a more lethal strain, such as the H5N1 virus. Nonetheless, it’s likely that this situation can be reversed if doctors and patients are more vigilant in prescribing and taking the drug, respectively.
With regards to the side effect issue, it would be interesting to see if Glaxo’s neuramindiase inhibitor Zanamir, causes the same problems. I suspect it won’t since unlike Tamiflu, which is an oral drug, Zanamivir is poorly absorbed and thus must be given by inhalation where only 4 to 17% of the drug is systemically absorbed. When talking about treating the flu, this is fine because the virus is located in the respiratory tract. Therefore, if it turns our that the Tamiflu side-effects are caused by the drug and that they are related to the drug’s mechanism, Zanamivir could offer a safer alternative since there would be less systemic exposure.