Topic: Pandemic (H1N1) 2009 (Human Swine Influenza) - Oseltamivir (Tamiflu) information for prescribers
Description
Treatment with oseltamivir (Tamiflu) may prevent infection with Human Swine influenza ("Swine flu"), or shorten the duration and severity of illness in people that already have Human Swine influenza.
Note: Information adapted from CDC Interim Guidelines, Product Information and NSW Fact sheet
Introduction
Human Swine influenza ("Swine flu") is a respiratory disease of pigs caused by type A influenza (H1N1). Swine flu viruses do not normally infect humans, however, human infections with swine flu have occurred in the past, and cases of human-to-human spread of a swine flu virus have recently been confirmed.
The most useful antiviral medications for treating and preventing infection with influenza are neuraminidase inhibitors. Queensland Health has access to Oseltamivir (trade name: Tamiflu) stocks for the control of any outbreak of this illness.
Antiviral Resistance
This virus is sensitive (susceptible) to the neuraminidase inhibitor antiviral medication oseltamivir but resistant to both amantadine and rimantadine.
Antiviral Treatment
Confirmed and suspected cases
Recommendations for use of antivirals may change as data on antiviral susceptibilities and additional advice on the optimal use of the medications becomes available.
Empiric antiviral treatment should be considered for confirmed, probable or suspected cases of H1N1 Influenza 09 (Human Swine Influenza) virus infection. Treatment of hospitalised patients and patients at higher risk for influenza complications should be prioritised. For the latest case definitions check http://www.healthemergency.gov.au/internet/healthemergency/publishing.nsf/Content/healthprof
Antiviral treatment with oseltamivir should be initiated as soon as possible after the onset of symptoms. Evidence for benefits from treatment in studies of seasonal influenza is strongest when treatment is started within 48 hours of illness onset. However, some studies of treatment of seasonal influenza have indicated benefit, including reductions in mortality or duration of hospitalisation even for patients whose treatment was started more than 48 hours after illness onset.
Recommended duration of treatment is five days. Antiviral doses recommended for treatment of Human Swine Influenza virus infection in adults or children 1 year of age or older are the same as those recommended for seasonal influenza. (see table)
Antiviral Chemoprophylaxis
Recommendations regarding the use of antiviral chemoprophylaxis will change regularly as information regarding the nature of the virus and its infectivity become clear. It is best to regularly check the web http://www.healthemergency.gov.au/internet/healthemergency/publishing.nsf/Content/healthprof for the latest advice as to whom should received this intervention.
Duration of antiviral chemoprophylaxis post-exposure is 10 days after the last known exposure to an affected area or ill confirmed case of swine influenza A (H1N1) virus infection.
Currently, there is no recommendation for the use of oseltamivir as pre-exposure prophylaxis for the swine influenza virus. Should recommendations be made for pre-exposure protection, chemoprophylaxis should be given during the potential exposure period and continued for 10 days after the last known exposure to an affected area or ill confirmed case of swine influenza A (H1N1) virus infection.
Adults & children 13 yrs and over
Treatment: Oseltamivir 75 mg capsule twice per day for 5 days
Chemoprophylaxis: Oseltamivir 75 mg capsule once per day for 10 days after last known exposure
Children (12 months to 12 yrs)*
-
Children under or equal to 15 kg
Treatment: Oseltamivir 30 mg twice daily for 5 days
Chemoprophylaxis: Oseltamivir 30 mg once daily for 10 days after last known exposure -
Children 15-23 kg
Treatment: Oseltamivir 45 mg twice daily for 5 days
Chemoprophylaxis: Oseltamivir 45 mg once daily for 10 days after last exposure -
Children 24-40 kg
Treatment: Oseltamivir 60 mg twice daily for 5 days
Chemoprophylaxis: Oseltamivir 60 mg once daily for 10 days after last exposure -
Children over 40 kg
Treatment: Oseltamivir 75 mg twice daily for 5 days
Chemoprohylaxis: Oseltamivir 75 mg once daily for 10 days after last exposure
* The pharmacokinetics of oseltamivir in children aged less than 1 year has not been thoroughly assessed. Advice from a specialist paediatrician should be sought in these cases.
Pregnant Women
Excess deaths among pregnant women were documented during the pandemics of 1918-19 and 1957-58. Pregnancy can increase the risk for serious medical complications of influenza. Oseltamivir is a "Pregnancy Category B1" medication, indicating that no clinical studies have been conducted to assess the safety of this medication for pregnant women. Because of the unknown effects of influenza antiviral drugs on pregnant women and their foetuses, oseltamivir should be used during pregnancy only if the potential benefit justifies the potential risk to the embryo or foetus. No adverse effects have been reported among women who received oseltamivir during pregnancy or among infants born to women who have received oseltamivir. Pregnancy should not be considered a contraindication to oseltamivir use.
Breast Feeding
There are no human studies investigating potential effects on breastfed babies when women are treated with antiviral drugs. It is recommended that antiviral drugs be used if the potential benefit of taking the drug exceeds the potential risks to the baby.
Impaired Renal Function
Oseltamivir cannot be used by people on dialysis.
Adverse events and contraindications
There are no known cross reactions between oseltamivir and other drugs. Babies with fructose intolerance may react to the Sorbitol in oseltamivir. Use of this drug should be considered if indicated in consultation with the baby’s Paediatrician. Please refer to full product information for further details.
Related links
Queensland Health human swine flu site http://www.health.qld.gov.au/swineflu/html/facts.asp
Last updated: 12 May 2009
Last Updated: 11th May, 2010
Date Valid to: 31st December, 2010
