see also:

• influenza
• zanamivir (Relenza)
• Western Health influenza pandemic information
• Tamiflu Data Sheet approved by NZ Medsafe 3th March 2009

• see EMJA June 2009 - ASID/TSANZ guidelines
• Australasian Society for Infectious Diseases (ASID)
• Swine Influenza Task Force of the Thoracic Society of Australia and New Zealand (TSANZ)

• Neuraminidase inhibitors (oseltamivir and zanamivir) are the antiviral agents of choice for H1N1 influenza 09.
• In otherwise healthy children and adults with confirmed or suspected influenza, antiviral treatment is of greatest benefit when given within 48 hours of symptom onset.
• Treatment should be prioritised for patients with risk factors for severe disease, such as older people (> 65 years), pregnant women, patients with chronic disease (eg, asthma, cardiorespiratory disease, diabetes and renal failure) or immunosuppression, and young children.
• Antiviral treatment can be given to children as young as 1 year. However, animal studies suggest central nervous system accumulation of oseltamivir in infants < 1 year. Parents should be informed of the possibility of uncommon neuropsychiatric adverse events among children.
• Antiviral treatment should be offered to pregnant women with suspected or confirmed influenza because of the risk of severe disease in this group; there is limited evidence suggesting safety during pregnancy.
• Antiviral treatment should be given to hospitalised patients with severe influenza infection (especially pneumonia), even > 48 hours after symptom onset. Antibiotics should be given to such patients according to established guidelines for community-acquired pneumonia.

• Antiviral prophylaxis can be given to health care workers and close contacts of patients with influenza following exposure, and to residents of institutions to terminate outbreaks. Contacts not provided with prophylaxis should have access to early treatment with antiviral agents.
• Long-term prophylaxis can be given to “first responder” health care workers for durations of up to 6 weeks for oseltamivir and 4 weeks for zanamivir. Use of antiviral prophylaxis for these groups should be in the context of agreement to use the national stockpile.

• according to FDA product information sheet (pdf):
  • Tamiflu 75mg bd 5 days shortens median time to improvement of symptoms on seasonal influenza A by 1.3 days if started within 40hrs of onset of illness.
  • Tamiflu 75mg daily for 7 days reduced lab-confirmed seasonal influenza A in post-exposure contacts from 12% in placebo group to 1% in treated group when Tamiflu was started within 2 days of onset of symptoms in the index case.
  • Tamiflu 75mg daily for 42 days in elderly residents in nursing homes (80% of whom had been vaccinated) reduced seasonal influenza A rates from 4.4% to 0.4%.
  • Tamiflu 75mg daily for 42 days in unvaccinated adolescents and adults reduced seasonal influenza A rates from 4.8% to 1.2%.
• Tamiflu is NOT effective for viruses other than influenza A or B - ie. it will NOT help with a common cold.

• see http://www.cdc.gov/H1N1flu/clinician_pregnant.htm
• pregnant women with suspected or confirmed H1N1 influenza should be commenced on empirical antiviral Rx (eg. Tamiflu) ASAP if within 1st 48 hours of illness although studies suggest some benefit even for those starting Rx after the 1st 48hrs.
• pregnant women who are exposed to H1N1 should be offered prophylaxis with Tamiflu as with non-pregnant adult patients.
• encourage lactation even whilst taking Tamiflu as benefits to infant appear to outweigh risks

• Tamiflu should only be given to patients who have developed H1N1 influenza if either:
  • within 1st 48 hours of onset (with priority given to high risk group including age > 65yrs, young children 1-5 years age, pregnancy, chronic illness such as heart or lung disease), or,
  • those hospitalised with influenza irrespective of duration of illness.

• The recommended oral dose of Tamiflu capsules in adults and adolescents 13 years of age and older is 75 mg twice daily for five days. Adults and adolescents 13 years of age and older who are unable to swallow capsules may receive the appropriate dose of Tamiflu suspension.

• children aged under 12 months - discuss with a paediatric infectious diseases expert
• For the oral suspension, an oral dosing dispenser with 30, 45 and 60 mg graduations is provided; the 75 mg dose can be measured using a combination of 30 and 45 mg. It is recommended that patients use this dispenser.
• Paediatric Patients weighing > 40 kg who are able to swallow capsules may also receive treatment with a 75 mg capsule twice daily or one 30 mg capsule plus one 45 mg capsule twice daily as an alternative to the recommended dose of Tamiflu suspension.
• Tamiflu suspension dose for those who cannot swallow a 75mg capsule:

• Household or equivalent contacts will only require prophylaxis if they are they are in a vulnerable setting, or are a high risk patient.
• vulnerable settings include:
  • child care centres with baby rooms (under 12 months of age)
  • special schools
  • aged care centres
  • supported residential services (SRCs)
  • hospitals
• high risk individuals include:
  • chronic respiratory conditions (eg. asthma, COPD)
  • pregnant women
  • morbid obesity
  • indigenous people of any age
  • conditions predisposing to severe influenza:
    • cardiac disease (not simple hypertension)
    • chronic illness such as diabetes mellitus, chronic metabolic disease, chronic renal disease, haemoglobinopathies, immunosuppression (HIV, cancers, drugs) or chronic neurologic conditions.

• The recommended oral dose of Tamiflu for prevention of influenza following close contact with an infected individual is 75 mg once daily for ten days.
• Ideally therapy should begin within two days of exposure.
• The recommended dose for prevention during a community outbreak of influenza is 75 mg once daily.
• Safety and efficacy have been demonstrated for up to six weeks.
• The duration of protection lasts for as long as dosing is continued.

• Children weighing > 40 kg, who are able to swallow capsules, may also receive prophylaxis with a 75 mg capsule once daily or one 30 mg capsule plus one 45 mg capsule once daily for ten days as an alternative to the recommended dose of Tamiflu suspension (see below).
• The recommended prophylactic oral dose of Tamiflu suspension for children greater than or equal to 1 year of age is shown in the table above but give once a day not bd.
• For the oral suspension a dosing syringe marked with 30, 45 and 60 mg dosing levels is provided.

• guidelines provided by Roche dated 27th May 2009, but as Tamiflu is NOT approved in Australia by the TGA for this method of administration, Roche Products cannot endorse the use of any method of administration which is not covered by TGA approval.
• THUS, the following is for use only during emergency situations and NOT for use if TGA-approved suspension is available.

• dose: 75mg
• hold one Tamiflu 75mg capsule over a small bowl, carefully pull the capsule open and pour powder into the bowl.
• add a suitable, small amount (1 teaspoon maximum) of sweetened food product such as regular or sugar-free chocolate syrup, honey, light brown or table sugar dissolved in water, dessert toppings, sweetened condense milk, apple sauce or yoghurt to mask the bitter taste.
• stir well and swallow entire contents of micture immediately after preparation.
• if there is some residual in container, rinse with small amount of water and drink - it is not necessary to dissolve the powder.

• hold one Tamiflu 75mg capsule over a small bowl, carefully pull the capsule open and pour powder into the bowl.
• using a graduated syringe, add 5ml water to the powder and stir for about 2 minutes.
• draw up into a syringe the correct dose (see table above) of this mixture (1ml = 15mg Tamiflu)
• empty contents of this syringe into a SECOND bowl
• in this second bowl, add a suitable, small amount (1 teaspoon maximum) of sweetened food product such as regular or sugar-free chocolate syrup, honey (only for children 2 years and older), light brown or table sugar dissolved in water, dessert toppings, sweetened condense milk, apple sauce or yoghurt to mask the bitter taste.
• stir the mixture and give entire contents immediately after its preparation.
• if there is some residual in container, rinse with small amount of water and drink - it is not necessary to dissolve the powder.