Tamiflu

Generic Name: Oseltamivir phosphate
Product Name: Tamiflu

Indication: What Tamiflu is used for

Tamiflu is used to treat influenza (flu) in selected adults and children aged over 12 months. It is also used to prevent influenza in individuals aged over 12 months.

Treatment with Tamiflu results in shortening of symptom duration by one day, and reduces by half a day the time to return to work.  Tamiflu reduces the occurrence of complications associated with influenza infection, such as pneumonia.

Action: How Tamiflu works

Oseltamivir (Tamiflu) inhibits an enzyme (neuraminidase) that is found on the surface of the influenza virus. Disabling this enzyme reduces multiplication and spread of viral particles in the body. This reduces the length of time the body is affected by influenza, and reduces the risk of complications due to spread of the infection.

Dose advice: How to use Tamiflu

Dose information

• Treatment with Tamiflu should begin within 24 hours, and not later than 48 hours after onset of influenza symptoms. The earlier treatment starts, the lesser the severity and shorter the duration of the illness;
• Influenza prophylaxis should begin within two days of exposure;
• Tamiflu may be taken with or without food; however, taking it with food may make taking the drug more tolerable for some people;
• Avoid direct contact of Tamiflu with the skin and eyes;
• Tamiflu is not predicted to have any adverse effect on driving performance or the ability to operate machinery;
• Uncomplicated influenza should be treated by resting, drinking plenty of fluid, and paracetamol (e.g. Panadol) for pain relief.

Capsules

Treatment of influenza with Tamiflu capsules

Adults:

• Swallow one 75 mg capsule in the morning and one at night for 5 days.

Children older than one year of age:

• Children who weigh less than 40 kg will be prescribed a lower dose capsule.
• Your doctor or pharmacist will tell you how many capsules to swallow in the morning and night.
• Treatment is also for 5 days in children.

Prophylaxis (prevention) of influenza with Tamiflu capsules

Adults:

• Swallow one 75 mg capsule in the morning for 10 days.

Children greater than one year of age:

• Children who weigh less than 40 kg will be prescribed a lower dose capsule.
• Your doctor or pharmacist will tell you how many capsules to swallow in the morning.
• Therapy is for 10 days.

Suspension

Tamiflu suspension may be used by adults, adolescents, and children who are unable to swallow capsules.

Instructions for use of the suspension are as follows:

1. Shake the closed bottle of Tamiflu well before use.
2. Push the plunger of the dispenser (syringe) completely down toward the tip (so there is no air in it).
3. Remove the cap from the Tamiflu bottle.
4. Insert the tip of the dispenser into the bottle at the adaptor.
5. Turn the bottle and dispenser upside down together.
6. Slowly pull out the plunger to the mark on the dispenser that equals the dose that the doctor or pharmacist has instructed you to take.
7. Turn the bottle and dispenser upright.
8. Slowly remove the dispenser from the Tamiflu bottle.
9. Push the suspension directly into the mouth by pushing down the plunger of the dispenser. Swallow the medicine. You can eat or drink after taking the medication if you like.
10. Immediately after swallowing the Tamiflu, take the dispenser apart and rinse both parts under running tap water.

Depending on the dose you have been prescribed, you may have some leftover suspension in the bottle following the complete treatment course of Tamiflu.

Treatment of influenza with Tamiflu suspension

Adults:

• 75 mg morning and night for 5 days.
• This is taken as 6.25 mL of the suspension in the morning, and 6.25 mL at night, using the provided oral dispenser as described above.

Children greater than one year of age:

• Children who weigh less than 40 kg will be prescribed a lower dose suspension.
• Your doctor or pharmacist will tell you how much suspension to swallow in the morning and night.
• Treatment is for 5 days in children.

Prophylaxis (prevention) of influenza with Tamiflu suspension

Adults:

• 75 mg once daily for 10 days, taken as 6.25 mL using the provided oral dispenser.

Children greater than one year of age:

•  Children who weigh less than 40 kg will be prescribed a lower dose suspension.
• Your doctor or pharmacist will tell you how much suspension to swallow in the morning for the 10 days of therapy.

If you have any questions about the correct way to use Tamiflu capsules or suspension, speak to your doctor.

Contraindications

Tamiflu should not be used by:

• Children aged less than one year;
• Individuals who are known to be hypersensitive to any of the product components.

Precautions

Tamiflu should be used with caution in people with:

• Complicated influenza (e.g. viral or bacterial pneumonia);
• Kidney problems (renal impairment);
• Significant liver problems (hepatic impairment);
• Chronic cardiac or respiratory disease;
• Fructose intolerance. Tamiflu suspension contains 2.6 g of sorbitol within a daily dose, which is above the recommended daily maximum limit of sorbitol for those with hereditary fructose intolerance;
• Elderly age.

Use in pregnancy

Tamiflu is ADEC Category B1. Insufficient studies are available to prove safety in pregnant women or their developing foetus, though animal studies show no teratogenic effects thus far. Consequently, the use of Tamiflu during pregnancy must be carefully considered, and instigated only if the benefits are thought to outweigh the risks.

Lacation

It is unknown whether Tamiflu is excreted into human breast milk. Excretion in the breast milk of lactating rats is known to occur, though offspring development was not affected. Tamiflu should only be used in breastfeeding mothers if the benefit to the mother outweighs the risk to the breastfed infant.

Schedule of Tamiflu

Tamiflu is Schedule 4 (prescription only medicine).

Common side effects of Tamiflu

All medicines have side effects. Most commonly the side effects are minor; however, some can be more serious. Usually the benefits of taking a medication outweigh the associated side effects. Your doctor would have considered these side effects before starting you on Tamiflu.

Common side effects are those that occur in more than 1% of patients given Tamiflu. These include:

• Nausea;
• Vomiting;
• Diarrhoea;
• Abdominal pain;
• Headache;
• Insomnia;
• Dizziness;
• Fatigue;
• Upper respiratory tract infections.

Uncommon side effects of Tamiflu

Side effects that occur in less than 1% of patients given Tamiflu are considered rare. Patients do not necessarily experience any of these side effects, so do not become alarmed by this list:

• Rash;
• Allergic reactions;
• Neuropsychiatric symptoms, mainly occurring in children (e.g. abnormal behaviour, hallucinations, delirium);
• Raised liver enzymes;
• Aggravation of asthma;
• Dermatitis;
• Swollen lymph nodes (lymphadenopathy);
• Tympanic membrane (eardrum) disorders;
• Conjunctivitis;
• Bleeding of the gastrointestinal tract.

Very rare side effects associated with Tamiflu use include:

• Stevens-Johnson syndrome;
• Erythema multiforme;
• Toxic epidermal necrolysis.

If you experience any of the listed side effects, or any other symptoms which appear abnormal or unusual, please tell your doctor.

For further information talk to your doctor.

More information

For more information on the common cold and influenza, types of influenza and treatments and tips for preventing influenza, see Cold and Flu.

References

1. Rossi S [ed]. Oseltamivir [online]. Adelaide: Australian Medicines Handbook. 2009 [cited 2 May 2009]. Available from: [URL Link]
2. Product Information: Tamiflu (oseltamivir phosphate) [online]. Roche. 1 May 2009 [cited 2 May 2009]. Available from: [URL Link]
3. Antibiotic Expert Group. Influenza. In: Therapeutic Guidelines: Antibiotic. Version 13. Melbourne: Therapeutic Guidelines Limited; 2006.
4. Tamiflu [online]. MIMS Australia. 2009 [cited 2 May 2009]. Available from: [URL Link]
5. Consumer Medicine Information: Tamiflu Capsules [online]. Roche. 1 May 2009 [cited 2 May 2009]. Available from: [URL Link]
6. Consumer Medicine Information: Tamiflu Suspension [online]. Roche. 18 August 2008 [cited 2 May 2009]. Available from: [URL Link]
7. Gubareva LV, Kaiser L, Hayden FG. Influenza virus neuraminidase inhibitors. Lancet. 2000; 355(9206): 827-35.