Tamiflu: a beginner's guide

What does it do?
Tamiflu, and the less talked-about Relenza, are antiviral drugs. They slow down the rate at which viruses infect cells in your body and, therefore, how fast they spread and make you ill. Antiviral drugs do this by stopping the virus producing an enzyme called neuraminidase — hence they are called neuraminidase inhibitors.

But my doctor always told me that he couldn’t prescribe drugs for viruses
Antibiotics kill bacteria. They don’t affect viruses. Antivirals do affect viruses, but they don’t get rid of them, just slow them down. Viruses are tougher and trickier than bacteria because they take over your cells — injecting their genetic material into ours and making our cells produce millions of viruses, each capable of invading other cells. Antivirals aren’t magic bullets and are not as effective as antibiotics at controlling infections. On the other hand, the body’s natural defences are good at tackling viruses, so GPs tend to leave it to nature and don’t prescribe antivirals in normal circumstances because if they’re used too often viruses don’t respond to them any more. But in situations where viral infection may be life-threatening they can be the best tool a doctor has.

Don’t they have nasty side-effects?
The warnings on the packet are scary It’s always hard to get the side-effects of any drug into proportion given the list of possible reactions that companies are obliged to list. Research indicates that the main side -effects of Tamiflu are nausea, vomiting and retching. Relenza brings the risk of diarrhoea. Generally, these antivirals are “well-tolerated”. There have been isolated reports of antivirals inducing suicidal thoughts, confusion and hallucinations, but these have not yet been well researched, so a firm link has not been made.

Why aren’t we already using Tamiflu for normal seasonal flu?
We are. Official guidance recommends antiviral medicines to treat seasonal flu for those whose lives might at risk if they became infected because of age or long-term illness. They’re widely used to treat, and prevent, seasonal flu in Japan and America. But British authorities have decided to be sparing in their use because viruses become resistant to antivirals if they’re overused. There are already indications that seasonal flu viruses aren’t responding to Tamiflu.

Why is Tamiflu being given to anyone in contact with swine flu, even if their symptoms are mild or non-existent?
Antivirals have two effects. First, they can lessen your symptoms and give your body a better chance of fighting the virus. Second, they can actually slow down the rate of an epidemic or pandemic spreading. They do this by slowing down the speed with which viruses proliferate in the body: in people who already have symptoms this means that fewer viruses get coughed and spluttered over other people; and in people who do not yet have symptoms it stops the virus reproducing as soon as it gets into their bodies, so that they may never develop symptoms.

So as well as simply to save lives, the authorities are keen that people take Tamiflu to — hopefully — slow the pandemic. Unlike seasonal flu, pandemic flu needs drastic action to halt it.

While scientists can predict the type of virus that is going to cause seasonal flu from year to year, and to develop vaccines accordingly, pandemic flu is something completely new that springs up from animals, making it less predictable and less easy to develop vaccines for. Antivirals suddenly become a useful short-term tool in these changed circumstances.

Does that mean that my family has little to gain from taking Tamiflu?
Given that swine flu doesn’t seem to be endangering life in the UK at the moment, this is a subject that scientists are beginning to debate. The main argument for taking Tamiflu is that you need to catch the virus early: it won’t help you at all if you take it more than 48 hours after symptoms such as sudden fever or cough have started. If you take Tamiflu, the symptoms may stay mild. If you don’t, they may escalate into something more serious and it will be too late to do anything about it.

Equally, if those around you take Tamiflu, it may stop the virus developing in them, if and when they become infected. Some people might consider the risks of side-effects to be greater than the risk of the illness. A more significant argument against taking antivirals is that unnecessary use will contribute to the possibility of swine flu developing resistance.

Bear in mind that privately bought Tamiflu is already being widely used against the advice of doctors, and the virus is likely to develop immunity to it at some stage. Once it does, there is evidence that Relenza will remain resistant and can be brought in as a second-line treatment.

So should we take it?
Yes, if you have been advised to. If you are unsure, talk to your doctor as soon as possible, as any delay in taking Tamiflu can render it useless. It will be your decision, but your doctor can make recommendations on the basis of past medical history and other knowledge of the flu outbreak. If you’re worried about your child suffering side-effects, talk to your doctor about possibly starting with a reduced dose.

Isn’t there an argument for getting flu over with, rather than stopping it with Tamiflu?
No. Taking antivirals doesn’t stop your body from creating antibodies to the swine flu virus, which should defend you if there is a second wave of influenza later in the year. Though some research has raised the possibility of antivirals impairing the immune system’s ability to fight other viruses or infections, there is no evidence for this.

Isn’t it silly to hand out Tamiflu only to those with swine flu and their direct contacts? Wouldn’t their wider social circle benefit?
Antiviral drugs aren’t easily produced, and stocks are limited. Plus the Government is worried about Tamiflu resistance developing, if everyone starts using it. So a line has to be drawn, even though some experts privately acknowledge it is largely arbitrary.

So just how strong is the scientific evidence behind the effectiveness of Tamiflu in countering a flu pandemic?
The truth is there is no evidence of the effectiveness of Tamiflu, or any other antiviral, in the face of a flu pandemic. There have never been circumstances in which to test them.

The most comprehensive scientific assessment of Tamiflu and Relenza, produced by the Cochrane Collaboration this year, found that though they were effective in preventing or curtailing symptoms and complications of seasonal influenza, it was currently impossible to gauge their effectiveness in a pandemic, and little evidence to suggest that they would stop its spread. But it still recommended their use. For the time being, they’re the best we’ve got.

Sources: Dr Andrew Watts, lecturer in medicinal chemistry, University of Bath; Professor Peter Dunnill, chairman of the Advanced Centre for Biochemical Engineering, University College London; the Cochrane Collaboration review: “Neuraminidase inhibitors for preventing and treating influenza in healthy adults”