Dear Dr. K – I heard that there is a new drug to treat flu. Is that true? And, does it work?

Dear Dr. K – I heard that there is a new drug to treat flu. Is that true? And, does it work?

Yes, and yes.  The new drug is Xofluza and it is the first flu drug with a new mechanism of action to come along in 20 years.  It is (hold on to your hat) a polymerase acidic endonuclease inhibitor, (PAEI).  PAEI is essential for the viral RNA messenger that allows the flu virus to replicate itself.  By shutting down viral replication, it shuts down the infection.  It is effective for both influenza A and B.

 

The only other available drugs for influenza all work by the same, but different than Xofluza, mechanism which is to inhibit neuraminidase.  These drugs are:  Tamiflu, Relenza and Rapivab.  Neuraminidase is an enzyme of the virus that allows it to escape from one human cell so it can invade the next cell.  By inhibiting neuraminidase these drugs also shut down the infection.  Tamiflu is oral, Relenza is a nasal spray and Rapivab is IV (used in hospitalized, severely ill patients).

 

The new drug works as well, but not better than the other three.  However, one dose is sufficient.  It works best if started within 48 hours of becoming ill.  Being new it is naturally more expensive.  Unfortunately, influenza seems to be able to develop resistance to the new drug fairly quickly.  Ten percent of patients developed resistance after a single dose.

 

Resistance is also a problem with the neuraminidase inhibitors, so the FDA is studying the possibility of combining both families of drugs for their synergism (killing virus by different mechanisms) and as a means to prevent resistance.


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