Please refer to Upper respiratory tract infections for guidance on the prescribing of oseltamivir or zanamivir for the treatment and prophylaxis of influenza.

Amantadine is not recommended for the treatment and prophylaxis of influenza (See NICE TA158 and NICE TA168).

Resources:

• UKHSA Guidance on use of antivirals for the treatment and prophylaxis of influenza includes summary algorithm for prescribing antiviral treatment (page 29), testing, clinical at-risk groups, post-exposure prophylaxis, dosing in renal dysfunction, and use in pregnancy
• UKHSA Management of acute respiratory infection outbreaks in care homes guidance
• Information on the dominant circulating strain can be found in UKHSA's weekly influenza reports

Prescribing antivirals for influenza

• The DHSC provides annual notification, usually through the CMO, of the start and end of the season when influenza is circulating in the community. GPs may prescribe antivirals for the treatment of influenza during this time period.
• Antiviral treatment outside of the flu season, and prophylaxis (at any time), is provided through a commissioned service and should not be routinely prescribed by GPs.

Oseltamivir

• Capsules 30mg, 45mg, 75mg (£15.41 = 10 x 75mg)
• Oral suspension sugar free 6mg/ml (£10.27 = 50ml) (see note 4)

Indications and dose

• Treatment of influenza
  • Adults and adolescents 13 years and older:
    • Body-weight 41kg and above: 75mg twice daily for 5 days (10 days if immunocompromised)
    • Body-weight up to 41kg: 60mg twice daily for 5 days (10 days if immunocompromised)
    • Renal impairment:
      • eGFR 10 to 60mL/min/1.73m²: refer to BNF
      • eGFR <10mL/min/1.73m²: recommendations vary between sources, seek specialist advice
  • Child below 13 years of age: refer to BNFc
  • Treatment should begin within 48 hours of onset of symptoms
• Post-exposure prophylaxis of influenza (via locally commissioned service)
  • Adults and adolescents 13 years and older:
    • Body weight 41kg and above: 75mg once daily for 10 days
    • Body weight up to 41kg: 60mg once daily for 10 days
    • Renal impairment:
      • eGFR 10 to 60mL/min/1.73m²: refer to BNF
      • eGFR <10mL/min/1.73m²: recommendations vary between sources, seek specialist advice
  • Child below 13 years of age: refer to BNFc
  • Treatment should begin within 48 hours of exposure to an infected person

Notes

1. Treatment of influenza: use oseltamivir in all cases except in the severely immunocompromised where the predominate circulating strain is H1N1 or the infection is with an oseltamivir resistant strain (UKHSA guidance, see algorithm page 29).
2. Post-exposure prophylaxis of influenza: refer to UKHSA guidance.
3. The above dosing regimens are taken from the BNF/BNFc.
4. Oral suspension: UKHSA advises that oseltamivir oral suspension should be reserved for children under the age of 1 year. Children over 1 year of age, adults with swallowing difficulties, and those receiving nasogastric oseltamivir, should use capsules which can be opened and mixed into an appropriate sugary liquid; instructions are given in the Patient Information Leaflet.
5. Pregnancy: UKHSA advise that oseltamivir remains the first line option for the vast majority of pregnant women with influenza, including during seasons that are dominated by influenza H1N1. Seek specialist advice for pregnant women who meet additional criteria for requiring zanamivir first line (e.g. severely immunocompromised and H1N1 is the predominant circulating strain). For further information refer to UKHSA guidance. UKTIS guidance is available here: Use of oseltamivir in pregnancy.
6. Breastfeeding: refer to SPS: Using oseltamivir and zanamivir during breastfeeding.
7. Endorse prescription ‘SLS’.
8. NICE TA158: Oseltamivir, amantadine (review) and zanamivir for the prophylaxis of influenza (September 2008).
9. NICE TA168: Amantadine, oseltamivir and zanamivir for the treatment of influenza (February 2009).

Zanamivir

• Inhalation powder blisters with device 5mg (£16.36 = 20 blister units)
• Solution for infusion vials 200mg/20ml 

Indications and dose

• Treatment of influenza
  • Adults and children 5 years and older: two inhalations twice daily for 5 days
  • Treatment should begin within 48 hours of onset of symptoms for adults, and within 36 hours after onset of symptoms for children
• Post-exposure prophylaxis of influenza (via locally commissioned service)
  • Adults and children 5 years and older: two inhalations once daily for 10 days
  • Treatment should begin within 36 hours of exposure to an infected person

Notes

1. Treatment of influenza: use oseltamivir (above) in all cases except in the severely immunocompromised where the predominate circulating strain is H1N1 or the infection is with an oseltamivir resistant strain (UKHSA guidance, see algorithm page 29).
2. Post-exposure prophylaxis of influenza: refer to UKHSA guidance.
3. Asthma and chronic obstructive pulmonary disease:
   1. Zanamivir should not be administered to patients with severe asthma unless close medical monitoring and appropriate clinical facilities are available in case of bronchoconstriction.
   2. Should zanamivir be considered appropriate for patients with asthma or COPD, the patient should be informed of the potential risk of bronchospasm with zanamivir and should have a short-acting bronchodilator available. Patients on maintenance inhaled bronchodilating therapy should be advised to use their bronchodilators before taking zanamivir.
4. Pregnancy: UKHSA guidance advises that oseltamivir remains the first line option for the vast majority of pregnant women with influenza, including during seasons that are dominated by influenza H1N1. For pregnant women who meet additional criteria for requiring zanamivir first line, seek advice from a local infection specialist. The SmPC advises that due to limited data, it is preferable to avoid zanamivir. UKTIS guidance is available here: Use of zanamivir during pregnancy.
5. Breastfeeding: refer to SPS: Using oseltamivir and zanamivir during breastfeeding.
6. Endorse prescription ‘SLS’.
7. NICE TA158: Oseltamivir, amantadine (review) and zanamivir for the prophylaxis of influenza (September 2008).
8. NICE TA168: Amantadine, oseltamivir and zanamivir for the treatment of influenza (February 2009).