Family doctor

Use: For the flu (influenza A and B)

Relenza contains zanamivir and Tamiflu contains oseltamivir. These anti-viral medicines work against an enzyme on the surface of the influenza virus, called neuraminidase (new-ram-in-ee-daze). This enzyme helps new pieces of virus leave the cells of the body that are already infected by the virus, therefore these medicines reduce the amount of virus in the breathing passages (e.g. throat).

The influenza viruses are different from the cold viruses and therefore there is no benefit from taking Relenza or Tamiflu for a cold, they only help the flu.

In studies, people with the flu who were given these anti-virals had their symptoms last less time than people who did not use them, e.g. they may have felt bad for 4 days if using Relenza instead of 5 days in people not using Relenza. This improvement seemed to be more obvious for people who have high temperature (fever) with their flu. These medicines may reduce time off work and also may reduce complications from the flu such as bronchitis and pneumonia.

The main difference between Relenza and Tamiflu is how they are taken. Relenza is inhaled from a diskhaler and Tamiflu comes in capsules that are swallowed.

Relenza is inhaled from a device called a diskhaler. Two inhalations are used twice a day for five days, and it is recommended that treatment be started as soon as possible after symptoms have occurred, preferably within two days. Follow the directions in the pack, fitting the disk with four doses into the diskhaler, then taking two doses at a time; change the disk when all doses on the disk have been used.

One Tamiflu capsule is swallowed twice a day for five days, starting on the first or second day of flu symptoms. Some people may like to take it with food to help avoid stomach upset, but this is not essential.

Cautions:

• Relenza disks contain zanamivir and lactose, and should not be used in people with an allergy to either ingredient. Anyone with an allergy to oseltamivir should not take Tamiflu.
• Take special care using Tamiflu in people with kidney problems.
• Patients with asthma or other lung problems can very rarely have a problem with tightening of airways when using Relenza. Keep your reliever inhaler (beta-agonist, e.g. Ventolin) with you at all times in case this could happen.
• Relenza and Tamiflu are not recommended for use during pregnancy or breastfeeding unless the likely benefits outweigh the possible risks.

Side effects:

• In studies, the side effects of Relenza were no greater than in those using the pretend (placebo) disks instead of the medicine.
• A very uncommon side effect of Relenza is tightening of airways.
• Only very little Relenza leaves the airways and moves into the bloodstream.
• Nausea and vomiting are possible side effects of Tamiflu.
• There may be other side effects, so if you have any unexpected symptoms while taking this medicine, tell your doctor or pharmacist.

Interactions:

Interactions are unlikely.

Patient information:

• Follow the instructions on the label of the medicine or as directed by your doctor.
• Start to use the medicine as soon as possible after the flu symptoms start to get the most benefit.
• Relenza and Tamiflu will not help with a cold.
• Complete the five-day course and don't miss any doses.

Differences between a cold and the flu

Some differences between colds and flus are:

• The flu is likely to keep you in bed feeling very exhausted, while a cold makes you feel tired but you can usually get out of bed.
• The flu is more likely to give you a high temperature and a headache than a cold.
• Body aches and pains can be quite severe with the flu whereas with a cold they are very minor or not at all.
• The flu occurs suddenly while a cold is usually more gradual.

Editorial note:

These drugs are not funded by governments in New Zealand or the UK. This means the patient has to meet the full cost.

Difficulties in using it are raised because it is hard to distinguish influenza from other milder viruses without rapid reliable tests which are not yet widely available.

The benefit in higher risk groups (e.g. the elderly and people with respiratory problems) is not clearly known.

The current best strategy includes vaccination of high risk groups to reduce the risk of complications and death from influenza.