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Antimicrobials

Oseltamivir

Guidelines for use

TAMIFLU MEDICAL DIRECTIVE

Pharmacists may order prophylaxis by implementing the Medical Directive (MED-0062): Pharmacist Ordering of Oseltamivir (Tamiflu®) Prophylaxis for Inpatient Influenza Outbreaks

Active against: Influenza A & B

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1. Clinical Use

Appropriate Uses:

  • Treatment of influenza for a maximum of 5 days. Although the Tamiflu prescribing information states that treatment should be initiated within 2 days of onset of symptoms, there is evidence of continued benefit in hospitalized patients when initiation of therapy is delayed beyond 2 days
  • Prophylaxis against the spread of influenza among inpatients in a patient care area where an outbreak of influenza has been declared by Infection Prevention & Control (IP&C) should continue until IP&C has declared an end to the outbreak
  • Prophylaxis of unvaccinated staff during an inpatient outbreak as decided by IP&C

Inappropriate Uses:

  • Initiation of treatment for patients with a mid-turbinate swab positive for a respiratory virus other than influenza

2. Precautions

  • Efficacy of oseltamivir for treatment or prevention of influenza in immunocompromised patients has not been established
  • Pregnancy: Not expected to increase risk of major congenital malformations. Plasma concentrations of the active metabolite of oseltamivir were found to be lower in pregnant women. Possible reasons for this include: the increase in renal blood flow and GFR and/or the increase in volume of distribution in pregnancy. The clinical significance of this is unclear. However, shortening the dosing interval or increasing the dose may warrant consideration.
  • Breastfeeding: Not expected to present any major safety issues

3. Adverse Effects

  • Nausea, vomiting and abdominal pain

4. Dosage

Treatment Prophylaxis
CrCl unknown 75 mg BID; to be re-assessed when CrCl known 75 mg now; then 75 mg once daily; to be re-assessed when CrCl known
CrCl > 60 mL/min 75 mg BID 75 mg now; then 75 mg once daily
CrCl 30 - 60 mL/min: 45 mg BID 45 mg now; then 45 mg once daily
CrCl 10 - 29 mL/min: 45 mg once daily 45 mg now; then 45 mg q 2 days
ESRD (CrCl < 10 mL/min): 75 mg now; then one additional 75 mg dose on day 3 45 mg now; then 45 mg q 3 days
PD: 75 mg now; then one additional 75 mg dose on day 3 45 mg now; then 45 mg q 3 days
HD:

75 mg now; then 75 mg after each of the next 2 HD

45 mg now; then 45 mg post-HD x 3 doses per week

CRRT: 45 mg BID 45 mg now; then 45 mg once daily

5. Duration of Therapy

  • Treatment: 5 days
  • Prophylaxis: Until IP&C has declared an end to outbreak, or 7 days for patients in a room with someone who has been diagnosed with influenza
  • If patient is discharged, prophylaxis should continue for 7 days from last presumed exposure to influenza. For example:
    • Patient being discharged from outbreak floor: 7 additional days, regardless of length of prophylaxis already administered
    • Patient being discharged after exposure to infected roommate: 7 days from the date of last exposure to influenza

Last updated: March 2018