Dosing and uses of Tamiflu (oseltamivir)
Adult dosage forms and strengths
capsule
- 30mg
- 45mg
- 75mg
powder for oral suspension
- 6mg/mL
Influenza A and B Prophylaxis
75 mg PO qDay for at least 10 days
Dosing considerations
- Initiate within 48 hours of exposure
- For community outbreak, may administer for up to 6 weeks
Influenza A and B Treatment
75 mg PO q12hr x5 days
Dosing considerations
- Initiate within 48 hours of influenza symptom onset
H1N1 Influenza A (Swine Flu) Prophylaxis (Off-label)
75 mg PO qDay
Dosing considerations
- Postexposure prophylaxis: Initiate within 7 days of exposure and continue for at least 10 days
- Preexposure prophylaxis (community outbreak): Initiate during potential exposure period and continue for 10 days after last known exposure
H1N1 Influenza A (Swine Flu) Treatment (Off-label)
75 mg PO q12hr x5 days
Dosing considerations
- Initiate within 48 hours of influenza symptom onset
Dosing Modifications
Renal impairment (CrCl 10-30 mL/min)
- Prophylaxis: 75 mg PO qOD, OR 30 mg PO qDay
- Treatment: 75 mg PO qDay x5 days
Renal impairment (CrCl <10 mL/min)
- Administer with caution
Pediatric dosage forms and strengths
capsule
- 30mg
- 45mg
- 75mg
powder for oral suspension
- 6mg/mL
Influenza A and B Prophylaxis
<1 year: Safety and efficacy not established for prophylaxis
≥1 year
- <15 kg: 30 mg PO qDay x10 days
- 15-23 kg: 45 mg PO qDay x10 days
- 23-40 kg: 60 mg PO qDay x10 days
- >40 kg: 75 mg PO qDay x10 days
Dosing considerations
- Start within 2 days of exposure
Influenza A and B Treatment
<2 weeks: Safety and efficacy not established for treatment
Aged 2 weeks to <1 year
- 3 mg/kg PO BID x5 days
≥1 year
- <15 kg: 30 mg PO q12hr x5 days
- 15-23 kg: 45 mg PO q12hr x5 days
- 23-40 kg: 60 mg PO q12hr x5 days
- >40 kg: 75 mg PO q12hr x5 days
Dosing considerations
- Start within 24-48 hours of symptom onset
H1N1 Influenza A (Swine Flu) Prophylaxis (Off-label)
<1 year
- <3 months: Data limited; not recommended unless situation judged critical
- 3-5 months: 20 mg PO qDay x10 days
- 6-11 months: 25 mg PO qDay x10 days
≥1 year
- <15 kg: 30 mg PO qDay x10 days
- 15-23 kg: 45 mg PO qDay x10 days
- 23-40 kg: 60 mg PO qDay x10 days
- >40 kg: Administer as in adults
H1N1 Influenza A (Swine Flu) Treatment (Off-label)
Acute illness and age <1 year
- <3 months: 12 mg PO q12hr x5 days
- 3-5 months: 20 mg PO q12hr x5 days
- 6-11 months: 25 mg PO q12hr x5 days
Acute illness and age ≥1 year
- <15 kg: 30 mg PO q12hr x5 days
- 15-23 kg: 45 mg PO q12hr x5 days
- 23-40 kg: 60 mg PO q12hr x5 days
- >40 kg: Administer as in adults
Tamiflu (oseltamivir) adverse (side) effects
1-10%
Abdominal pain
Conjunctivitis
Ear disorder
Epistaxis
Insomnia
Nausea
Vomiting
Vertigo
<1%
Aggravation of diabetes
Anemia
Arrhythmia
Confusion
Delirium
Hemorrhagic colitis
Hepatitis
Humerus fracture
Peritonsillar abscess
Pneumonia
Pseudomembranous colitis
Pyrexia
Rash
Seizure
Transaminases increased
Toxic epidermal necrolysis
Unstable angina
Swelling of face or tongue
Postmarketing Reports
Hypothermia
Diaper rash (2 weeks to <1 year of age)
Dermatitis
Urticaria
Eczema
Stevens-Johnson Syndrome
Erythema multiforme
Gastrointestinal bleeding
Abnormal liver function tests
Warnings
Contraindications
Hypersensitivity
Cautions
Use caution in patients with chronic cardiac disease, severre hepatic impairment, renal imapairment, respiratory disease
Most effective when used within 24-48 hr of onset of symptoms
Age <1 year: Safety and efficacy for PROPHYLAXIS of influenza has not been established
Oral suspension should be mixed prior to dispensing
Safety and efficacy in immunocompromised patients not established
Therapy is not a substitute for influenza virus vaccine
Serious skin/hypersensitivity reactions such as Stevens-Johnson Syndrome, toxic epidermal necrolysis and erythema multiforme; discontinue therapy and initiate appropriate treatment if allergic-like reactions occur or are suspected
Patients with influenza, including those receiving therapy, particularly pediatric patients, may be at an increased risk of confusion or abnormal behavior early in their illness, potentially fatal neuropsychiatric adverse events; monitor for signs of abnormal behavior
Prescribers should be alert to potential for secondary bacterial infections and treat them as appropriate
Oral suspension and hereditary fructose intolerance
- Fructose can be harmful to patients with hereditary fructose intolerance
- One dose of 75 mg oral suspension delivers 2 g of sorbitol; this is above the daily maximum limit of sorbitol for patients with hereditary fructose intolerance, and may cause dyspepsia and diarrhea
Pregnancy and lactation
Pregnancy category: C
Prompt use of antiviral drugs during the 2009 H1N1 influenza pandemic improved survival among severely ill pregnant women; the CDC examined reports of severe flu (resulting in death or ICU admission) in 347 pregnant women during the pandemic; only 4 women (7%) of those who died received an antiviral within 2 days of symptom onset, compared with 41% of survivors. (MMWR Sept 9, 2011;60[35]:1192-6)
Lactation: Unknown; use caution
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Tamiflu (oseltamivir)
Mechanism of action
Inhibits viral neuraminidases; stops release of virus from cells and prevents virus from crossing mucous lining of respiratory tract
Absorption
Bioavailability: 75%
Peak plasma time: 2.5-6 hr
Distribution
Protein bound: 3% (oseltamivir carboxylase); 42% (oseltamivir)
Vd: 23-26 L
Elimination
Half-life: 1-3hr (oseltamivir); 6-10 hr (oseltamivir carboxylate)
Excretion: Feces; urine (>90% as oseltamivir carboxylate)
Administration
Oral Administration
Tablets and oral suspension may be take with or without food
Tolerability may be enhanced if taken with food
Emergency Preparation of Oral Suspension from 75 mg Capsules
Instructions below are for 100 mL of 6 mg/mL suspension
1. Place 7 mL of distilled water into a polyethyleneterephthalate (PET) or glass bottle
2. Empty content of eight 75-mg capsules (ie, 600 mg) into bottle
3. Gently swirl the suspension to ensure adequate wetting of the powder for at least 2 minutes
4. Slowly add 91 mL of Ora-Sweet, cherry syrup, or simple syrup
5. Close bottle and shake well for about 30 minutesInstruct patient to shake well before use
Stable for 5 days at room temperature or 5 weeks refrigerated at 2-8°C (36-46°F)
