Oseltamivir

Administration

• Type: Antiviral
• Routes of Administration: Oral
• Common Trade Names: Tamiflu

Adult Dosing

Influenza

• 75mg PO BID x 5 days

Pediatric Dosing

Influenza

• Age <1 year: 3mg/kg PO BID x 5 days
• <15kg: 30mg PO BID x 5 days
• 15-23kg: 45mg PO BID x 5 days
• 24-40kg: 60mg PO BID x5d
• Adult: 75mg PO BID x 5 days

Special Populations

• Pregnancy Rating: Category C
• Lactation risk: Low concentrations of oseltamivir seen in breast milk; levels are unlikely to lead to toxicity in a breast-fed infant. The manufacturer recommends that caution be used if administered to a nursing woman.
• High Risk for Complications and Recommended for Treatment per CDC:
  • Children < 2 yo
  • Adults > 65 yo
  • Chronic Pulmonary Disease including Asthma
  • Cardiovascular disease (excluding hypertension only)
  • Renal, hepatic, hematological, and metabolic disorders (including sickle cell, diabetes)
  • Neurological and Neurodevelopmental disorders (brain disorders, spinal cord, peripheral nerve disorders, cerebreal palsy, epilepsy, stroke, MR, developmental delay, muscular dystrophy)
  • Immunosuppressed including on HAART
  • Pregnant or Postpartum (2 weeks after delivery)
  • <19 yo on long term aspirin
  • American Indians/Alaskan natives
  • Morbid Obesity (BMI >= 40)
  • Nursing home or chronic care facility residents.

Renal Dosing

• CrCl >31 to 60 mL/minute: 30mg BID for 5 days
• CrCl >11 to 30 mL/minute: 30mg qday for 5 days
• ESRD on HD CrCl≤10 mL/minute: 30mg after every hemodialysis cycle (treatment duration not to exceed 5 days)
• ESRD patients on Continuous Ambulatory Peritoneal Dialysis CrCl≤10 mL/minute: Single 30mg dose administered immediately after dialysis exchange

Hepatic Dosing

• efficacy in hepatic impairment has not been established

Chemoprophylaxis

• In general, Centers for Disease Control does not recommend seasonal or pre-exposure antiviral chemoprophylaxis, but can be considered in certain situations:
  • Patients at high risk of influenza complications during the first two weeks following vaccination after exposure to a person with influenza.
  • Patients who cannot receive influenza vaccine due to a contraindication after exposure to a person with influenza.
  • Prevention for people with severe immune deficiencies or others who might not respond to influenza vaccination, such as people receiving immunosuppressive medications, after exposure to a person with influenza.
• To be effective as chemoprophylaxis, an antiviral medication must be taken each day for the duration of potential exposure to a person with influenza and continued for 7 days after the last known exposure. For people taking antiviral chemoprophylaxis after inactivated influenza vaccination, the recommended duration is until immunity after vaccination develops (antibody development after vaccination takes about two weeks in adults and can take longer in children depending on age and vaccination history).
• Antiviral chemoprophylaxis generally is not recommended if more than 48 hours have elapsed since the first exposure to a person with influenza.

Contraindications

• Allergy to class/drug

Adverse Reactions

Serious

• dysrhythmia
• erythema multiforme/TEN/SJS
• GI bleed, hepatitis
• seizure, delirium

Common

• abdominal pain, nausea/vomiting, diarrhea
• Insomnia

Pharmacology

• Half-life: 1-3h
• Metabolism:
• Excretion:

Mechanism of Action

• inhibits viral neuroaminidase→ interferes with viral particle release

Comments

• Influenza
  • Shortens duration of illness by 16.8 hrs while NNTH (number needed to harm) was 28 in regards to causing nausea and vomiting, HA, and renal and psych syndromes
  • Greatest benefit if within 48hrs of symptom onset
    • However, may be beneficial up to 4-5 days, including in pregnant patients
    • Early treatment of hospitalized patients can reduce death