INFLUENZA treatments under scrutiny

THE CASE

The US Food and Drug Administration (FDA) and Roche pharmaceuticals met last November to discuss the incidence of psychiatric disturbances and even suicide deaths related to osteltamivir (Tamiflu). The results of these discussions have just been made public, along with recommendations that the consumer drug information be modified to include specific warnings.

Meanwhile, GlaxoSmithKline the manufacturers of the competing influenza treatment drug zanamivir (Relenza), are concerned that their product is also associated with psychiatric changes, but so far no deaths have been linked to Relenza. GlaxoSmithKline says that the evidence so far is circumstantial and does not definitely indicate a connection.

The common thread is that the neurological problems are seen mainly in children. Apparently twenty-five patients under the age of twenty-on have died, most of them in Japan. Five of these deaths were from children falling from balconies or running into moving traffic. All of the deaths were related to Tamiflu and not to Relenza, but both are associated with neurological problems.

The main difference between the two drugs, is that Tamuflu is taken orally in capsule or liquid form, while Relenza is inhaled directly into the lungs using a special inhalation device. Possibly the Relenza is mainly retained in the lungs rather than being distributed to the whole body as is Tamiflu.

Because of the patchy occurrence of these neurological side effects, other factors may be at play, such as genetic differences in the Japanese population or even that some strains of influenza may cause these behavioral changes. These need to be ruled out before the drugs are blamed.

The current Australian Consumer Medical Information (CMI dated April 2007) for Tamiflu says:

"People with influenza including those taking TAMIFLU may be at an increased risk of confusion and in rare cases accidental injury. Please ensure that you monitor how you are feeling throughout the treatment period. Your doctor should be contacted immediately if you notice any signs of unusual behavior."

The latest CMI for Relenza, dated August 2007, does not mention anything about behavioural changes.

MY VERDICT

Even though there is a paucity of information about the neurological changes caused by taking Tamiflu and Relenza, let's play it safe. The CMI for both products needs updating to include a specific warning of the potential for these drugs to cause neurological changes in children. TGA are you awake?

NOTE

Neither of these drugs are subsidised under the Australian Pharmaceutical Benefits Scheme (PBS).