Monday, September 13, 2010

Study: Antiviral Therapy For H5N1


# 4896



One of the ongoing debates in the world of pandemic influenza has been on the value of Oseltamivir (Tamiflu) for pandemic influenza.


Critics point out that the drug can have (rare) side effects and that it only reduces the duration of seasonal flu symptoms by an average of 1.3 days.    A modest but measureable benefit.


Where Tamiflu – and other antivirals – appear to make a bigger difference is in reducing symptoms in those who have pre-existing risk factors or conditions – including pregnancy – or those who are experiencing serious influenza complications.


And among H5N1 bird flu cases around the world, those that have survived (40%) were likely to have received early antiviral intervention.


Granted, most of the `evidence’ for the effectiveness of antivirals comes from observational studies, which some researchers find wanting (see BMJ: A Review Of Tamiflu’s Efficacy Against Seasonal Influenza).


Randomized controlled trials (RCTs) – while considered the `gold standard’ for drug research – are almost impossible to conduct ethically when trying to evaluate a potentially life saving drug.


We would all like medicine to be based on treatments and drugs provedbeyond a shadow of a doubt – to be safe and effective . . . but sometimes we must accept a lower burden of proof -the preponderance of evidence - instead.



Earlier this year, another observational study appeared in JAMA  (see Study: Antivirals Saved Lives Of Pregnant Women) that strongly suggested that Tamiflu was life saving for some patients with pandemic flu.


Today we’ve the largest study yet on the outcomes of H5N1 patients who either received, or did not receive, antiviral treatment.  


The research appears in the IDSA’s  Journal of Infectious Diseases along with a companion editorial (h/t Tetano on FluTrackers for the link)



DOI: 10.1086/656316

Effectiveness of Antiviral Treatment in Human Influenza A(H5N1) Infections: Analysis of a Global Patient Registry

Wiku Adisasmito,Paul K. S Chan,Nelson Lee, Ahmet Faik Oner,Viktor Gasimov,Faik Aghayev, Mukhtiar Zaman, Ebun Bamgboye, Nazim Dogan, Richard Coker, Kathryn Starzyk, Nancy A. Dreyer, and Stephen Toovey



While I would encourage you to read the entire study (and editorial) the bottom line is essentially out of 308 cases studied, the overall survival rate was a dismal 43.5%.

But . . . of those who received at least one dose of Tamiflu . . .  60% survived . . .  as opposed to only 24% who received no antivirals.





The greatest benefit was derived when treatment was started within 48 hours of falling ill, but even delayed treatment was seen to have some value.


Treatment with oseltamivir was linked to a 49% reduction in mortality.


As this study, and the editorial comment point out, longer courses of antivirals and at higher doses may be needed to improve survival these rates. 


The `Double the Dose for Double The Duration’ option is something that we’ve discussed many times in the past ( see Hong Kong Finds Success With Higher Tamiflu Doses and How Much Tamiflu Is Enough?)



Today’s study, however, gives us the best evidence to date that antivirals can, and do, save lives when used in the treatment of H5N1 infections. 

1 comment:

Anonymous said...

waouh... we have read a lot of silly things written by non-doctors and doctors themselves on the inefficiency of Tamiflu for influenza (old studies about seasonnal flu.. )
thank you.