So, are the neuraminidase inhibitors (Tamiflu and Relenza, oseltamivir and zanamivir) going to be of any use against bird flu? The press coverage is a mass of confusion. Headlines range from stuff like "Newer Flu Drugs Work Better" to "Don't Use Older Flu Drugs, Experts Warn" to "Tamiflu Not Effective Against Bird Flu". The problem is, we're looking at two different classes of drugs, and two different sorts of flu.

A few days ago the CDC issued a warning that the prevalent H3N2 flu strains this year have mutations that make the older class of flu antivirals (the aminoadamantanes) ineffective. But I'm not sure how many people even get these any more, since they were never very impressive to start with. I don't think anyone has seriously proposed them as a defense against H5N1 avian influenza, should that ever take off.

But Tamiflu and Relenza are a different story; a blizzard of hype has surrounded their possible use. Lost in the bird-flu noise is their use against "regular" influenza, a market where they've never performed up to expectations - no doubt they're selling rather better so far this season - and the CDC recommended their use for this purpose.

Comes now a report in The Lancet from a group in Rome (available to subscribers here), looking over all the published studies on the various drugs. They also recommend that that adamantanes be retired, and they aren't very positive on the use of the NA inhibitors against the standard forms of flu, which I'd say is in line with the clinical experience. And they found no evidence that either Tamiflu or Relenza is effective against bird flu, which leads to all the jumpy headlines.

But this isn't really a surprising finding, since there hasn't been (to my knowledge) any published study on the use of the drugs against avian influenza in humans. (Cell culture, yes, but that's a long way from the real world). There hasn't been enough time (and there haven't been enough patients, fortunately). A better headline would have been "Tamiflu's Effectiveness Against Bird Flu Unknown", but we already knew that. Didn't we?.