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Oseltamivir

Pronunciation

Pronunciation

(oh sel TAM i vir)

Index Terms

  • Oseltamivir Phosphate

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product

Capsule, Oral, as phosphate:

Tamiflu: 30 mg, 45 mg, 75 mg

Suspension Reconstituted, Oral, as base:

Tamiflu: 6 mg/mL (60 mL [DSC]) [contains saccharin sodium, sodium benzoate]

Tamiflu: 6 mg/mL (60 mL) [contains saccharin sodium, sodium benzoate; tutti-frutti flavor]

Brand Names: U.S.

  • Tamiflu

Pharmacologic Category

  • Antiviral Agent
  • Neuraminidase Inhibitor

Pharmacology

Oseltamivir, a prodrug, is hydrolyzed to the active form, oseltamivir carboxylate (OC). OC inhibits influenza virus neuraminidase, an enzyme known to cleave the budding viral progeny from its cellular envelope attachment point (neuraminic acid) just prior to release.

Absorption

Well absorbed

Distribution

Vd: 23 to 26 L (oseltamivir carboxylate); may be significantly increased in patients receiving ECMO (Lemaitre 2012; Mulla 2013)

Metabolism

Hepatic (90%) to oseltamivir carboxylate; neither the parent drug nor active metabolite has any effect on the cytochrome P450 system

Excretion

Urine (>99% as oseltamivir carboxylate); feces (<20%)

Half-Life Elimination

Oseltamivir: 1 to 3 hours; Oseltamivir carboxylate: 6 to 10 hours

Protein Binding

Plasma: Oseltamivir carboxylate: 3%; Oseltamivir: 42%

Special Populations: Renal Function Impairment

Exposure to the active metabolite is inversely proportional to declining renal function. In continuous ambulatory peritoneal dialysis (CAPD) patients, the peak concentration of the active metabolite following a single 30 mg oseltamivir dose or once weekly oseltamivir was 3-fold higher than in patients with normal renal function receiving the approved adult dose. Administration of 30 mg once weekly to CAPD patients resulted in plasma concentrations of active metabolite comparable to patients with normal renal function receiving the approved adult doses.

Special Populations: Elderly

Exposure to the active metabolite at steady state was 25% to 35% higher in elderly patients.

Special Populations: Children

Children ≤12 years of age clear the prodrug and active metabolite faster than adult patients, resulting in a lower exposure to a given mg/kg dose. The pharmacokinetics of the prodrug in patients >12 years of age are similar to adult patients.

Use: Labeled Indications

Prophylaxis of influenza: Prophylaxis of influenza (A or B) infection in patients ≥1 year of age.

Treatment of influenza: Treatment of uncomplicated acute illness due to influenza (A or B) infection in patients ≥2 weeks of age who have been symptomatic for no more than 48 hours.

The Advisory Committee on Immunization Practices (ACIP) recommends that treatment be considered for the following:

• Persons with severe, complicated or progressive illness

• Hospitalized persons

• Persons at higher risk for influenza complications:

- Children <2 years of age (highest risk in children <6 months of age)

- Adults ≥65 years of age

- Persons with chronic disorders of the pulmonary (including asthma) or cardiovascular systems (except hypertension)

- Persons with chronic metabolic diseases (including diabetes mellitus), hepatic disease, renal dysfunction, hematologic disorders (including sickle cell disease), or immunosuppression (including immunosuppression caused by medications or HIV)

- Persons with neurologic/neuromuscular conditions (including conditions such as spinal cord injuries, seizure disorders, cerebral palsy, stroke, mental retardation, moderate to severe developmental delay, or muscular dystrophy) which may compromise respiratory function, the handling of respiratory secretions, or that can increase the risk of aspiration

- Pregnant or postpartum women (≤2 weeks after delivery)

- Persons <19 years of age on long-term aspirin therapy

- American Indians and Alaskan Natives

- Persons who are morbidly obese (BMI ≥40)

- Residents of nursing homes or other chronic care facilities

• Use may also be considered for previously healthy, nonhigh-risk outpatients with confirmed or suspected influenza based on clinical judgment when treatment can be started within 48 hours of illness onset.

The ACIP recommends that prophylaxis be considered for the following:

• Postexposure prophylaxis may be considered for family or close contacts of suspected or confirmed cases, who are at higher risk of influenza complications, and who have not been vaccinated against the circulating strain at the time of the exposure.

• Postexposure prophylaxis may be considered for unvaccinated healthcare workers who had occupational exposure without protective equipment.

• Pre-exposure prophylaxis should only be used for persons at very high risk of influenza complications who cannot be otherwise protected at times of high risk for exposure.

• Prophylaxis should also be administered to all eligible residents of institutions that house patients at high risk when needed to control outbreaks.

The ACIP recommends that treatment and prophylaxis be given to children <1 year of age when indicated.

Limitations of use: Not a substitute for annual influenza vaccination. Consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use oseltamivir phosphate oral. Not recommended for patients with end-stage renal disease not undergoing dialysis.

Contraindications

Hypersensitivity to oseltamivir or any component of the formulation

Dosing: Adult

Influenza prophylaxis: Oral: 75 mg once daily; initiate prophylaxis within 48 hours of contact with an infected individual; duration of prophylaxis: 10 days (manufacturer recommendation) or alternatively 7 days (CDC [Influenza Antiviral Medications] 2014). During community outbreaks, duration of protection lasts for length of dosing period; safety and efficacy have been demonstrated for use up to 6 weeks in immunocompetent patients and safety has been demonstrated for use up to 12 weeks in patients who are immunocompromised.

Prophylaxis, institutional outbreak (CDC [Influenza Antiviral Medications] 2014): Continue for ≥2 weeks and until ~7 days after identification of illness onset in the last patient

Influenza treatment: Oral: 75 mg twice daily initiated within 48 hours of onset of symptoms; usual duration of treatment: 5 days. However, optimal duration is uncertain for severe or complicated influenza. Consider longer duration (eg, >5 days) of therapy in severely ill patients who remain severely ill after 5 days of therapy (CDC [Influenza Antiviral Medications] 2014).

Note: Data suggest that increased doses (>150 mg daily) in critically ill patients is not necessary since blood concentrations of oseltamivir were comparable or higher compared to ambulatory patients given similar dosing regimens (Ariano 2010; CDC [Influenza Antiviral Medications] 2014). Initiate as early as possible in any hospitalized patient with suspected/confirmed influenza regardless of the time of presentation from symptom onset (even if >48 hours) (CDC [Influenza Antiviral Medications] 2014); may be administered via naso- or orogastric tube in mechanically-ventilated patients (Taylor 2008).

Critically ill: Concurrent use of extracorporeal membrane oxygenation (ECMO) alone: No dosage adjustment necessary (Lemaitre 2012; Mulla 2013).

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Community-acquired pneumonia (influenza suspected or confirmed) (off-label use) (IDSA [Bradley 2011]): Oral:

Prophylaxis:

Infants 3 to 8 months: 3 mg/kg/day once daily

Infants ≥9 months to Children ≤23 months: 3.5 mg/kg/day once daily

Treatment:

Neonates and Infants ≤8 months: 6 mg/kg/day in divided doses twice daily

Infants ≥9 months to Children ≤23 months: 7 mg/kg/day in divided doses twice daily

Influenza prophylaxis: Oral: Initiate prophylaxis within 48 hours of contact with an infected individual

Manufacturer's labeling:

Children: 1 to 12 years:

≤15 kg: 30 mg once daily

>15 kg to ≤23 kg: 45 mg once daily

>23 kg to ≤40 kg: 60 mg once daily

>40 kg: 75 mg once daily

Adolescents ≥13 years: Refer to adult dosing.

Alternate recommendations:

American Academy of Pediatrics: Infants 0 to 11 months (off-label dosing; AAP 2013): Note: Do not exceed maximum dose of weight-based dosing; see manufacturer’s recommendation. Prophylaxis is not recommended for infants <3 months of age unless clinically critical.

0 to 8 months: 3 mg/kg/dose once daily

9 to 11 months: 3.5 mg/kg/dose once daily

Centers for Disease Control: Infants <12 months (off-label dosing) (CDC [Influenza Antiviral Medications] 2014): 3 mg/kg/dose once daily. Note: Do not exceed maximum dose of weight-based dosing; see manufacturer’s recommendation. Prophylaxis is not recommended for infants <3 months of age unless clinically critical. The current CDC weight-based dosing recommendation is not intended for premature neonates.

Infectious Disease Society of America/Pediatric Infectious Disease Society: Infants and Children 3 to 23 months (off-label dosing; Bradley 2011): Note: Do not exceed maximum dose of weight-based dosing; see manufacturer’s recommendation.

3 to 8 months: 3 mg/kg/dose once daily

9 to 23 months: 3.5 mg/kg/dose once daily

Prophylaxis duration:

Individual/household exposure:

Manufacturer's labeling: 10 days

Alternate recommendations: 7 days (CDC [Influenza Antiviral Medications] 2014); 10 days (AAP 2013)

Community/institutional outbreak: Note: The prescribing information states that during community outbreaks, duration of protection lasts for length of dosing period; safety and efficacy have been demonstrated for use up to 6 weeks in immunocompetent patients and safety has been demonstrated for use up to 12 weeks in patients who are immunocompromised.

Manufacturer's labeling: May be used for up to 6 weeks

Alternate recommendations: Continue for ≥2 weeks and until ~7 days after identification of illness onset in the last patient (CDC [Influenza Antiviral Medications] 2014) or until influenza activity in community subsides or immunity obtained from immunization (Bradley 2011).

Influenza treatment: Oral: Initiate treatment within 48 hours of onset of symptoms; usual duration of treatment is 5 days. However, optimal duration is uncertain for severe or complicated influenza. Consider longer duration (eg, >5 days) of therapy in severely ill patients who remain severely ill after 5 days of therapy. Note: Data suggest that increased doses in critically ill patients is not necessary since blood concentrations of oseltamivir were comparable or higher compared to ambulatory patients given similar dosing regimens (Ariano 2010; CDC [Influenza Antiviral Medications] 2014). Initiate as early as possible in any hospitalized patient with suspected/confirmed influenza regardless of the time of presentation from symptom onset (even if >48 hours) (CDC [Influenza Antiviral Medications] 2014); may be administered via naso- or orogastric tube in mechanically-ventilated patients (Taylor 2008).

US manufacturer's labeling: Note: The following dosing is also supported by some clinicians (Bradley 2011):

Infants ≥2 weeks: 3 mg/kg/dose twice daily

Children: 1 to 12 years:

≤15 kg: 30 mg twice daily

>15 kg to ≤23 kg: 45 mg twice daily

>23 kg to ≤40 kg: 60 mg twice daily

>40 kg: 75 mg twice daily

Adolescents ≥13 years: Refer to adult dosing.

Alternate recommendations:

American Academy of Pediatrics: Infants <12 months (off-label dosing; AAP 2013): Note: Age defined as postmenstrual age (first day of mother’s last period to birth plus the time elapsed after birth). Weight-based dosing recommendations for premature infants are lower than for term infants. Do not exceed maximum dose of weight-based dosing; see manufacturer’s recommendation.

Infants, premature:

<38 weeks: 1 mg/kg/dose twice daily

38 to 40 weeks: 1.5 mg/kg/dose twice daily

>40 weeks: 3 mg/kg/dose twice daily

Infants, term:

0 to 8 months: 3 mg/kg/dose twice daily

9 to 11 months: 3.5 mg/kg/dose twice daily

Centers for Disease Control: Infants <2 weeks (off-label dosing) (CDC [Influenza Antiviral Medications] 2014): 3 mg/kg/dose twice daily. Note: Do not exceed maximum dose of weight-based dosing; see manufacturer’s recommendation. The current CDC weight-based dosing recommendation is not intended for premature neonates.

Infectious Disease Society of America/Pediatric Infectious Disease Society: Infants and Children <24 months (off-label dosing; Bradley 2011): Note: Do not exceed maximum dose of weight-based dosing; see manufacturer’s recommendation.

Infants, premature: 1 mg/kg/dose twice daily

0 to 8 months: 3 mg/kg/dose twice daily

9 to 23 months: 3.5 mg/kg/dose twice daily

Dosing: Renal Impairment

Treatment: Adults:

CrCl >60 mL/minute: No dosage adjustment necessary.

CrCl >30 to 60 mL/minute: 30 mg twice daily

CrCl >10 to 30 mL/minute: 30 mg once daily

End-stage renal disease (ESRD) not undergoing dialysis: Use is not recommended (has not been studied).

Prophylaxis: Adults:

US labeling:

CrCl >60 mL/minute: No dosage adjustment necessary.

CrCl >30 to 60 mL/minute: 30 mg once daily

CrCl >10 to 30 mL/minute: 30 mg every other day

ESRD not undergoing dialysis: Use is not recommended (has not been studied).

Canadian labeling:

CrCl >60 mL/minute: No dosage adjustment necessary.

CrCl >30 to 60 mL/minute: 30 mg once daily

CrCl 10 to 30 mL/minute: 30 mg every other day

Intermittent hemodialysis (IHD) (CrCl ≤10 mL/minute):

Adults:

Treatment: 30 mg immediately and then 30 mg after every hemodialysis session for 5 days. Note: Assumes three hemodialysis sessions in the 5-day period.

Alternative recommendations: Treatment (AMMI Canada [Aoki 2012]):

Low-flux hemodialysis: 30 mg after each dialysis session for 5 days

High-flux hemodialysis: 75 mg after each dialysis session for 5 days

Prophylaxis:

US labeling: 30 mg immediately and then 30 mg after every other hemodialysis sessions for the recommended prophylaxis duration.

Canadian labeling: An initial 30 mg dose may be given prior to dialysis if exposed during the 48 hours between dialysis sessions. To maintain therapeutic concentrations, administer 30 mg after every other dialysis session over a period of 10 to 14 days.

Children >1 year (off-label dose; Schreuder 2010): Treatment:

≤15 kg: 7.5 mg after each hemodialysis session

>15 kg to ≤23 kg: 10 mg after each hemodialysis session

>23 kg to ≤40 kg: 15 mg after each hemodialysis session

>40 kg: 30 mg after each hemodialysis session

CAPD: Adults:

US labeling: CrCl ≤10 mL/minute:

Treatment: 30 mg immediately for one dose to provide a 5-day duration.

Prophylaxis: 30 mg immediately and then 30 mg once weekly for the recommended prophylaxis duration.

Canadian labeling:

Treatment: 30 mg once (prior to the start of dialysis) to provide a 5-day duration. Dose should be administered as soon as the determination has been made that treatment is necessary, regardless of when dialysis is scheduled.

Prophylaxis: 30 mg prior to start of dialysis, then 30 mg every 7 days for 10 to 14 days. Initial dose should be administered as soon as the determination has been made that prophylaxis is necessary, regardless of when dialysis is scheduled.

Continuous renal replacement therapy (CRRT) (high-flux):

Treatment (off-label dose; limited data): 30 mg once daily for 5 days or 75 mg every 48 hours to provide a 5-day duration (AMMI Canada [Aoki 2012]; Ariano 2010)

Prophylaxis (off-label): No data (AMMI Canada [Aoki 2012])

Continuous veno-venous hemodialysis (CVVHD): Adults: Note: Limited information available; optimal dosing has not been established: 150 mg twice daily administered via nasogastric or postpyloric feeding tube for suspected or confirmed H1N1 influenza demonstrated supratherapeutic oseltamivir carboxylate concentrations at effluent rates of 3,300 ± 919 mL/hour; the authors determined that the manufacturer recommended dosage of 75 mg once daily for patients with CrCl 10 to 30 mL/minute will likely achieve concentrations necessary to inhibit viral neuraminidase activity at these effluent rates; however, doses greater than 75 mg once daily may be required when using higher effluent rates (Eyler 2012).

CVVHD and concurrent use of ECMO: Adults: Lower oseltamivir carboxylate concentrations (~981 ng/mL) were observed as compared to those with the use of CVVHD alone (~2,760 ng/mL) when patients were administered 150 mg twice daily for suspected or confirmed H1N1 influenza (n=4; Eyler 2012).

Dosing: Hepatic Impairment

Mild-to-moderate impairment: No dosage adjustment necessary.

Severe impairment: No dosage adjustment provided in manufacturer’s labeling (has not been studied).

Dosing: Obesity

In adult morbidly obese patients (BMI >40 kg/m2), systemic exposure of oseltamivir carboxylate was not reduced; therefore, no dosage adjustment is necessary (Thorne-Humphrey 2011).

Reconstitution

Oral suspension: Reconstitute with 55 mL of water to a final concentration of 6 mg/mL (to make 60 mL total suspension).

Extemporaneously Prepared

If the commercially prepared oral suspension is not available, the manufacturer provides the following compounding information to prepare a 6 mg/mL suspension in emergency situations.

1. Place the specified amount of water into a polyethyleneterephthalate (PET) or glass bottle.

2. Carefully separate the capsule body and cap and pour the contents of the required number of 75 mg capsules into the PET or glass bottle.

3. Gently swirl the suspension to ensure adequate wetting of the powder for at least 2 minutes.

4. Slowly add the specified amount of vehicle to the bottle.

5. Close the bottle using a child-resistant cap and shake well for 30 seconds to completely dissolve the active drug.

6. Label “Shake Well Before Use.”

Stable for 35 days at 2°C to 8°C (36°F to 46°F) or 5 days at 25° C (77°F). The Canadian labeling suggests that preparations made with water containing preservative (ie, 0.05% sodium benzoate) are stable for 49 days at 2°C to 8°C (36°F to 46°F) and 10 days at 25°C (77°F). Shake gently prior to use. Do not dispense with dosing device provided with commercially-available product.

Preparation of Oseltamivir 6 mg/mL Suspension

Body Weight

Total Volume per Patient1

# of 75 mg Capsules2

Required Volume of Water

Required Volume of Vehicle2,3

Treatment Dose (wt based)4

Prophylactic Dose (wt based)4

1Entire course of therapy.

2Based on total volume per patient.

3Acceptable vehicles are cherry syrup (Humco®), Ora-Sweet® SF, or simple syrup.

4Using 6 mg/mL suspension.

≤15 kg

75 mL

6

5 mL

69 mL

5 mL (30 mg) twice daily for 5 days

5 mL (30 mg) once daily for 10 days

16 to 23 kg

100 mL

8

7 mL

91 mL

7.5 mL (45 mg) twice daily for 5 days

7.5 mL (45 mg) once daily for 10 days

24 to 40 kg

125 mL

10

8 mL

115 mL

10 mL (60 mg) twice daily for 5 days

10 mL (60 mg) once daily for 10 days

≥41 kg

150 mL

12

10 mL

137 mL

12.5 mL (75 mg) twice daily for 5 days

12.5 mL (75 mg) once daily for 10 days

Table has been converted to the following text.

Preparation of Oseltamivir 6 mg/mL Suspension

Weight-based details:

≤15 kg: To make a 6 mg/mL suspension, open six 75 mg capsules. Mix with 5 mL water and 69 mL vehicle to provide a total of 75 mL. Treatment dose is 5 mL (30 mg) twice daily for 5 days. Prophylactic dose is 5 mL (30 mg) once daily for 10 days.

16 to 23 kg: To make a 6 mg/mL suspension, open eight 75 mg capsules. Mix with 7 mL water and 91 mL vehicle to provide a total of 100 mL. Treatment dose is 7.5 mL (45 mg) twice daily for 5 days. Prophylactic dose is 7.5 mL (45 mg) once daily for 10 days.

24 to 40 kg: To make a 6 mg/mL suspension, open ten 75 mg capsules. Mix with 8 mL water and 115 mL vehicle to provide a total of 125 mL. Treatment dose is 10 mL (60 mg) twice daily for 5 days. Prophylactic dose is 10 mL (60 mg) once daily for 10 days.

≥41 kg: To make a 6 mg/mL suspension, open twelve 75 mg capsules. Mix with 10 mL water and 137 mL vehicle to provide a total of 150 mL. Treatment dose is 12.5 mL (75 mg) twice daily for 5 days. Prophylactic dose is 12.5 mL (75 mg) once daily for 10 days.

Canadian labeling:

Preparation of Oseltamivir 6 mg/mL Suspension: (using water with preservative (ie, 0.05% sodium benzoate)

Body Weight

Total Volume per Patient1

# of 75 mg Capsules2

Required Volume of Water (with preservative)

Treatment Dose (wt based)2,3

Prophylactic Dose (wt based)2,3

1Entire course of therapy.

2Using 6 mg/mL suspension.

3Measured dose should be mixed with an equal amount of sweetened liquid (eg, chocolate syrup, cherry syrup) to mask bitter taste.

≤15 kg

75 mL

6

74 mL

5 mL (30 mg) twice daily for 5 days

5 mL (30 mg) once daily for 10 days

16 to 23 kg

100 mL

8

98 mL

7.5 mL (45 mg) twice daily for 5 days

7.5 mL (45 mg) once daily for 10 days

24 to 40 kg

125 mL

10

123 mL

10 mL (60 mg) twice daily for 5 days

10 mL (60 mg) once daily for 10 days

≥41 kg

150 mL

12

147 mL

12.5 mL (75 mg) twice daily for 5 days

12.5 mL (75 mg) once daily for 10 days

Table has been converted to the following text.

Preparation of Oseltamivir 6 mg/mL Suspension

(using water with preservative (ie, 0.05% sodium benzoate)

Weight-based details:

≤15 kg: To make a 6 mg/mL suspension, open six 75 mg capsules. Mix with 74 mL water with preservative to provide a total of 75 mL. Treatment dose is 5 mL (30 mg) twice daily for 5 days. Prophylactic dose is 5 mL (30 mg) once daily for 10 days.

16 to 23 kg: To make a 6 mg/mL suspension, open eight 75 mg capsules. Mix with 98 mL water with preservative to provide a total of 100 mL. Treatment dose is 7.5 mL (45 mg) twice daily for 5 days. Prophylactic dose is 7.5 mL (45 mg) once daily for 10 days.

24 to 40 kg: To make a 6 mg/mL suspension, open ten 75 mg capsules. Mix with 123 mL water with preservative to provide a total of 125 mL. Treatment dose is 10 mL (60 mg) twice daily for 5 days. Prophylactic dose is 10 mL (60 mg) once daily for 10 days.

≥41 kg: To make a 6 mg/mL suspension, open twelve 75 mg capsules. Mix with 147 mL water with preservative to provide a total of 150 mL. Treatment dose is 12.5 mL (75 mg) twice daily for 5 days. Prophylactic dose is 12.5 mL (75 mg) once daily for 10 days.

Administration

May be administered without regard to meals; take with food to improve tolerance.

Capsules may be opened and mixed with sweetened liquid (eg, chocolate syrup, corn syrup, caramel topping, light brown sugar dissolved in water). Administer oral suspension using an oral dosing dispenser that measures the appropriate volume in milliliters; shake well before each use. When oral suspension is not available and/or age-appropriate strength of capsules are not available to mix with sweetened liquids, an extemporaneous preparation may be prepared (refer to “extemporaneously prepared” section of monograph for further details).

Mechanically ventilated critically ill patients: May administer via naso- or orogastric (NG/OG) tube. Dissolve powder from capsules in 20 mL of sterile water and inject down the NG/OG tube; follow with a 10 mL sterile water flush (Taylor 2008).

Dietary Considerations

Take without regard to meals; take with food to improve tolerance.

Storage

Capsules: Store at 25°C (77°F); excursions permitted to 15°C to 30°C (59°F to 86°F).

Oral suspension: Store powder for suspension at 25°C (77°F); excursions permitted to 15°C to 30°C (59°F to 86°F). Once reconstituted, store oral suspension under refrigeration at 2°C to 8°C (36°F to 46°F) or at room temperature; do not freeze. Use within 10 days of preparation if stored at room temperature or within 17 days of preparation if stored under refrigeration.

Drug Interactions

Influenza Virus Vaccine (Live/Attenuated): Antiviral Agents (Influenza A and B) may diminish the therapeutic effect of Influenza Virus Vaccine (Live/Attenuated). Management: Avoid anti-influenza antivirals during the period beginning 48 hours prior to and ending 2 weeks after vaccine administration. Persons receiving these agents within 2 weeks of the live intranasal spray vaccine should receive a repeat vaccine dose. Consider therapy modification

Probenecid: May increase serum concentrations of the active metabolite(s) of Oseltamivir. Management: Consider a change in therapy when using oseltamivir together with probenecid; reduced oseltamivir dose may be necessary. Increase monitoring for adverse events, such as thrombocytopenia. Consider therapy modification

Adverse Reactions

>10%: Gastrointestinal: Vomiting (2% to 15%)

1% to 10%:

Gastrointestinal: Nausea (4% to 10%), abdominal pain (2% to 5%), diarrhea (1% to 3%)

Ocular: Conjunctivitis (1%)

Respiratory: Epistaxis (1%)

<1% (Limited to important or life-threatening): Allergy, anaphylactic/anaphylactoid reaction, angina, arrhythmia, confusion, erythema multiforme, fracture, gastrointestinal bleeding, hemorrhagic colitis, hepatitis, liver function tests abnormal, neuropsychiatric events, pseudomembranous colitis, pyrexia, seizure, Stevens-Johnson syndrome, swelling of face or tongue, toxic epidermal necrolysis

Warnings/Precautions

Concerns related to adverse effects:

• Anaphylaxis/hypersensitivity: Rare but severe hypersensitivity reactions, including anaphylaxis and severe dermatologic reactions (eg, toxic epidermal necrolysis, Stevens-Johnson syndrome, erythema multiforme), have been associated with use. Discontinue use immediately if hypersensitivity occurs or is suspected and treat appropriately.

• Neuropsychiatric events: Rare occurrences of neuropsychiatric events (including confusion, delirium, hallucinations, and/or self-injury) have been reported primarily in pediatric patients from postmarketing surveillance; direct causation is difficult to establish (influenza infection may also be associated with behavioral and neurologic changes, in some cases resulting in fatal outcomes). These events may occur in the setting of encephalitis or encephalopathy but can occur without obvious severe disease. Monitor closely for signs of any unusual behavior.

Disease-related concerns:

• Cardiovascular disease: Use with caution in patients with chronic cardiac disease; efficacy has not been established.

• Hepatic impairment: Use with caution in patients with severe hepatic impairment; safety and efficacy have not been established.

• Renal impairment: Use with caution; dosage adjustment is required for patients with renal impairment. Not recommended for patients with end stage renal disease (ESRD) not undergoing dialysis.

• Respiratory disease: Use with caution in patients with respiratory disease; efficacy has not been established.

Special populations:

• Immunocompromised patients: Use with caution in immunocompromised patients; efficacy for treatment in immunocompromised patients have not been established. Safety for prophylaxis has been demonstrated for up to 12 weeks in this patient population.

• Pediatric: The Canadian labeling does not approve of use (treatment or prophylaxis) in infants <1 year of age.

Dosage form specific issues:

• Benzyl alcohol and derivatives: Some dosage forms may contain sodium benzoate/benzoic acid; benzoic acid (benzoate) is a metabolite of benzyl alcohol; large amounts of benzyl alcohol (≥99 mg/kg/day) have been associated with a potentially fatal toxicity (“gasping syndrome”) in neonates; the “gasping syndrome” consists of metabolic acidosis, respiratory distress, gasping respirations, CNS dysfunction (including convulsions, intracranial hemorrhage), hypotension, and cardiovascular collapse (AAP ["Inactive" 1997]; CDC, 1982); some data suggests that benzoate displaces bilirubin from protein binding sites (Ahlfors 2001); avoid or use dosage forms containing benzyl alcohol derivative with caution in neonates. See manufacturer’s labeling.

• Sorbitol: Oral suspension contains sorbitol (delivers ~2 g sorbitol per 75 mg dose) which is greater than the maximum daily limit for patients with hereditary fructose intolerance; may cause diarrhea and dyspepsia; use with caution.

Other warnings/precautions:

• Appropriate use: Oseltamivir is not a substitute for the influenza virus vaccine. It has not been shown to prevent primary or concomitant bacterial infections that may occur with influenza virus. Antiviral treatment should begin within 48 hours of symptom onset. However, the CDC recommends that treatment may still be beneficial and should be started in hospitalized patients with severe, complicated or progressive illness if >48 hours. Treatment should not be delayed while awaiting results of laboratory tests for influenza. Nonhospitalized persons who are not at high risk for developing severe or complicated illness and who have a mild disease are not likely to benefit if treatment is started >48 hours after symptom onset. Nonhospitalized persons who are already beginning to recover do not need treatment.

Monitoring Parameters

Signs or symptoms of unusual behavior, including attempts at self-injury, confusion, and/or delirium

Critically-ill patients: Repeat rRT-PCR or viral culture may help to determine on-going viral replication

Pregnancy Risk Factor

C

Pregnancy Considerations

Adverse events were observed in some animal reproduction studies. Oseltamivir phosphate and its active metabolite oseltamivir carboxylate cross the placenta (Meijer, 2012). An increased risk of adverse neonatal or maternal outcomes has generally not been observed following maternal use of oseltamivir during pregnancy (CDC, 60[1], 2011; CDC, March 13, 2014).

Untreated influenza infection is associated with an increased risk of adverse events to the fetus and an increased risk of complications or death to the mother. Neuraminidase inhibitors are currently recommended for the treatment or prophylaxis of influenza in pregnant women and women up to 2 weeks postpartum (CDC 60[1] 2011; CDC March 13, 2014; January 2015).

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience diarrhea, nausea, vomiting, or headache. Have patient report immediately to prescriber confusion, behavioral changes, difficulty speaking, tremors, seizures, hallucinations, or signs of Stevens-Johnson syndrome/toxic epidermal necrolysis (red, swollen, blistered, or peeling skin [with or without fever]; red or irritated eyes; or sores in mouth, throat, nose, or eyes) (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for healthcare professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.

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