oseltamivir

General

Pronunciation:
o-sel-tam-i-vir

Trade Name(s)

Tamiflu

Ther. Class.

antivirals

Pharm. Class.

neuraminidase inhibitors

Indications

Treatment of uncomplicated acute illness due to influenza infection in adults and children ≥2 wk who have had symptoms for ≤2 days.
Prevention of influenza in patients ≥1 yr.

Action

Inhibits the enzyme neuraminidase, which may alter virus particle aggregation and release.

Therapeutic Effect(s):

Reduced duration or prevention of flu-related symptoms.

Pharmacokinetics

Absorption: Rapidly absorbed from the GI tract; 75% reaches systemic circulation as the active drug.

Distribution: Well distributed to tissues.

Metabolism and Excretion: Rapidly metabolized by the liver to oseltamivir carboxylate, the active drug. >99% excreted unchanged in urine.

Half-life: Oseltamivir carboxylate: 6–10 hr.

TIME/ACTION PROFILE (plasma concentrations)

ROUTE	ONSET	PEAK	DURATION
PO	unknown	unknown	12 hr

Contraindication/Precautions

Contraindicated in:

Hypersensitivity;
End-stage renal disease and not receiving dialysis.

Use Cautiously in:

Renal impairment (↓ dose if CCr ≤60 mL/min);
Hereditary fructose intolerance (75 mg of oral suspension contains 2 g of sorbitol);
OB: Use during pregnancy only if potential material benefit justifies potential fetal risk;
Lactation: Use during breastfeeding only if potential maternal benefit justifies potential risk to infant;
Pedi: Children <2 wk (safety and effectiveness not established for treatment); children <1 yr (safety and effectiveness not established for prevention). Oral suspension contains sodium benzoate; avoid use in neonates.

Adverse Reactions/Side Effects

GI: nausea, vomiting

Neuro: abnormal behavior, agitation, confusion, delirium, hallucinations, insomnia, nightmares, SEIZURES, vertigo

Resp: bronchitis

* CAPITALS indicate life-threatening.
Underline indicate most frequent.

Interactions

Drug-Drug

May ↓ the therapeutic effect of influenza virus vaccine ; avoid use 2 days prior to and 2 wk after vaccine administration.

Route/Dosage

Treatment of Influenza

PO (Adults and Children ≥13 yr): 75 mg twice daily for 5 days.

PO (Children 1–12 yr and >40 kg): 75 mg twice daily for 5 days.

PO (Children 1–12 yr and 23.1–40 kg): 60 mg twice daily for 5 days.

PO (Children 1–12 yr and 15.1–23 kg): 45 mg twice daily for 5 days.

PO (Children 1–12 yr and ≤15 kg): 30 mg twice daily for 5 days.

PO (Infants 2 wk–<1 yr): 3 mg/kg/dose twice daily for 5 days.

Renal Impairment
PO (Adults): CCr 30–60 mL/min: 30 mg twice daily for 5 days; CCr 10–30 mL/min: 30 mg once daily for 5 days; CCr ≥10 mL/min and on hemodialysis: 30 mg after each hemodialysis session (not to exceed 5 days); CCr ≥10 mL/min and on peritoneal dialysis: 30-mg single dose immediately after a dialysis exchange; CCr <10 mL/min and not on dialysis: Not recommended.

Influenza Prevention

PO (Adults and Children ≥13 yr): 75 mg once daily for ≥10 days.

PO (Children 1–12 yr and >40 kg): 75 mg once daily for 10 days.

PO (Children 1–12 yr and 23.1–40 kg): 60 mg once daily for 10 days.

PO (Children 1–12 yr and 15.1–23 kg): 45 mg once daily for 10 days.

PO (Children 1–12 yr and ≤15 kg): 30 mg once daily for 10 days.

Renal Impairment
PO (Adults): CCr 30–60 mL/min: 30 mg once daily for ≥10 days; CCr 10–30 mL/min: 30 mg every other day for ≥10 days; CCr ≥10 mL/min and on hemodialysis: 30 mg after alternate hemodialysis sessions (treatment duration ≥10 days); CCr ≥10 mL/min and on peritoneal dialysis: 30 mg once weekly immediately after a dialysis exchange (treatment duration ≥10 days); CCr <10 mL/min and not on dialysis: Not recommended.

Availability (generic available)

Capsules: 30 mg, 45 mg, 75 mg

Oral suspension (tutti-frutti flavor): 6 mg/mL

Assessment

Monitor influenza symptoms (sudden onset of fever, cough, headache, fatigue, muscular weakness, sore throat). Additional supportive treatment may be indicated to treat symptoms.

Implementation

Treatment with oseltamivir should be started as soon as possible from the first sign of flu symptoms within 2 days of exposure.
- Consider available information on influenza drug susceptibility patterns and treatment effects before using oseltamivir for prophylaxis.
PO May be administered with food or milk to minimize GI irritation.
Use correct oral dosing device for measuring oral solution. Dosing errors have occurred due to oseltamivir dosing in mg and solution in mL. Make sure units of measure on prescription instructions match dosing device provided with the drug.
- If oral suspension is not available, capsules can be opened and mixed with flavored foods (regular or sugar-free chocolate syrup, corn syrup, caramel topping, light brown sugar dissolved in water). If correct dose and oral suspension are not available, pharmacist may compound emergency supply of oral suspension from 75 mg capsules.

Patient/Family Teaching

Instruct patient to take oseltamivir as soon as influenza symptoms appear and to continue to take it as directed, for the full course of therapy, even if feeling better. Take missed doses as soon as remembered unless within 2 hr of next dose. Do not double doses.
Caution patient that oseltamivir should not be shared with anyone, even if they have the same symptoms.
Advise patient that oseltamivir is not a substitute for a flu shot. Patients should receive annual flu shot according to immunization guidelines.
Advise patients to report behavioral changes (hallucinations, delirium, and abnormal behavior) to health care professional immediately.
Advise patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult with health care professional before taking other medications.
Rep: Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breastfeeding.

Evaluation/Desired Outcomes