Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.
Quick facts
- How it is given
- oral
- Type
- human prescription drug
- RxNorm ID
- 312122
We do not publish dosing. How much of this medicine to take, how often, and for how long depends on your age, weight, kidney and liver function, other conditions and other medicines. That is a decision for the person who prescribes or dispenses it. Follow the directions on your own pack and ask your pharmacist if anything is unclear.
What it is used to treat
Oseltamivir phosphate capsule is an influenza neuraminidase inhibitor (NAI) indicated for: Treatment of acute, uncomplicated influenza A and B in patients 2 weeks of age and older who have been symptomatic for no more than 48 hours. (1.1) Prophylaxis of influenza A and B in patients 1 year and older. (1.2) Limitations of Use : Not a substitute for annual influenza vaccination. (1.3) Consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use. (1.3) Not recommended for patients with end-stage renal disease not undergoing dialysis. (1.3) 1.1 Treatment of Influenza Oseltamivir phosphate capsules are indicated for the treatment of acute, uncomplicated illness due to influenza A and B infection in patients 2 weeks of age and older who have been symptomatic for no more than 48 hours. 1.2 Prophylaxis of Influenza Oseltamivir phosphate capsules are indicated for the prophylaxis of influenza A and B in patients 1 year and older. 1.3 Limitations of Use Oseltamivir phosphate capsules are not a substitute for early influenza vaccination on an annual basis as recommended by the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices. Influenza viruses change over time. Emergence of resistance substitutions could decrease drug effectiveness. Other factors (for example, changes in viral virulence) might also diminish clinical benefit of antiviral drugs. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use oseltamivir phosphate capsules [see Microbiology (12.4)] . Oseltamivir phosphate capsules are not recommended for patients with end-stage renal disease not undergoing dialysis [see Dosage and Administration (2.4) and Use in Specific Populations (8.6)].
About this medicine
Oseltamivir phosphate capsules, USP, an influenza neuraminidase inhibitor (NAI), are available as capsules containing 30 mg, 45 mg, or 75 mg of oseltamivir for oral use, in the form of oseltamivir phosphate, USP. In addition to the active ingredient, each capsule contains pregelatinized starch, croscarmellose sodium, povidone K-30, talc and sodium stearyl fumarate. The 30 mg and 75 mg capsule shell contains gelatin, iron oxide red, iron oxide yellow and titanium dioxide. The 45 mg capsule shell contains gelatin, ferrosoferric oxide and titanium dioxide. Each capsule is printed with blue ink, which contains shellac and FD&C Blue No. 2 Aluminium Lake as the colorant. Oseltamivir phosphate is a white to off white powder with the chemical name (3R,4R,5S)-4-acetylamino-5-amino-3(1-ethylpropoxy)-1-cyclohexene-1-carboxylic acid, ethyl ester, phosphate (1:1). The chemical formula is C 16 H 28 N 2 O 4 (free base). The molecular weight is 312.4 for oseltamivir free base and 410.4 for oseltamivir phosphate salt. The structural formula is as follows: Structure
How it works
12.1 Mechanism of Action Oseltamivir is an antiviral drug with activity against influenza virus [see Microbiology (12.4)].
Who should not take it
Oseltamivir phosphate capsules are contraindicated in patients with known serious hypersensitivity to oseltamivir or any component of the product. Severe allergic reactions have included anaphylaxis and serious skin reactions including toxic epidermal necrolysis, Stevens-Johnson Syndrome, and erythema multiforme [see Warnings and Precautions (5.1)] . Patients with known serious hypersensitivity to oseltamivir or any of the components of oseltamivir phosphate capsules (4)
Warnings and cautions
Serious skin/hypersensitivity reactions such as Stevens-Johnson Syndrome, toxic epidermal necrolysis and erythema multiforme: Discontinue oseltamivir phosphate capsules and initiate appropriate treatment if allergic-like reactions occur or are suspected. (5.1) Neuropsychiatric events: Patients with influenza, including those receiving oseltamivir phosphate capsules, particularly pediatric patients, may be at an increased risk of confusion or abnormal behavior early in their illness. Monitor for signs of abnormal behavior. (5.2) 5.1 Serious Skin/Hypersensitivity Reactions Cases of anaphylaxis and serious skin reactions including toxic epidermal necrolysis, Stevens-Johnson Syndrome, and erythema multiforme have been reported in postmarketing experience with oseltamivir phosphate capsules. Stop oseltamivir phosphate capsules and institute appropriate treatment if an allergic-like reaction occurs or is suspected. The use of oseltamivir phosphate capsules are contraindicated in patients with known serious hypersensitivity to oseltamivir phosphate capsules [see Contraindications (4) and Adverse Reactions (6.2)] . 5.2 Neuropsychiatric Events There have been postmarketing reports of delirium and abnormal behavior leading to injury, and in some cases resulting in fatal outcomes, in patients with influenza who were receiving oseltamivir phosphate capsules [see Adverse Reactions (6.2)] . Because these events were reported voluntarily during clinical practice, estimates of frequency cannot be made but they appear to be uncommon based on oseltamivir phosphate capsules usage data. These events were reported primarily among pediatric patients and often had an abrupt onset and rapid resolution. The contribution of oseltamivir phosphate capsules to these events has not been established. Influenza can be associated with a variety of neurologic and behavioral symptoms that can include events such as hallucinations, delirium, and abnormal behavior, 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. […]
Reported side effects
The following important adverse reactions are described below and elsewhere in the labeling: Serious skin and hypersensitivity reactions [see Warnings and Precautions (5.1)] Neuropsychiatric events [see Warnings and Precautions (5.2)] Most common adverse reactions (>1% and more common than with placebo): Treatment studies – Nausea, vomiting, headache. (6.1) Prophylaxis studies – Nausea, vomiting, headache, pain. (6.1) To report SUSPECTED ADVERSE REACTIONS, contact FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. Adverse Reactions from Treatment and Prophylaxis Trials in Adult and Adolescent Subjects (13 years of age and older) The overall safety profile of oseltamivir phosphate is based on data from 2,646 adult and adolescent subjects that received the recommended dosage of 75 mg orally twice daily for 5 days for treatment of influenza and 1,943 adult and adolescent subjects that received the recommended dosage of 75 mg orally once daily for up to 6 weeks for prophylaxis of influenza in clinical trials. The most common adverse reactions in the pooled treatment and pooled prophylaxis trials in adults and adolescents are displayed in Table 5. The majority of these adverse reactions were reported on a single occasion, occurred on either the first or second treatment day and resolved spontaneously within 1 to 2 days. This summary includes otherwise healthy adults/adolescents and subjects “at risk” (subjects at higher risk of developing complications associated with influenza, e.g., elderly patients and patients with chronic cardiac or respiratory disease). In general, the safety profile in the subjects “at risk” was qualitatively similar to that in otherwise healthy adults/adolescents. […]
Interactions with other medicines
Live attenuated influenza vaccine (LAIV), intranasal: Avoid administration of LAIV within 2 weeks before or 48 hours after oseltamivir phosphate capsules, use, unless medically indicated. (7) 7.1 Influenza Vaccines Live Attenuated Influenza Vaccine The concurrent use of oseltamivir phosphate capsules with live attenuated influenza vaccine (LAIV) intranasal has not been evaluated. However, because of the potential for oseltamivir phosphate capsules to inhibit replication of live vaccine virus and possibly reduce the efficacy of LAIV, avoid administration of LAIV within 2 weeks before or 48 hours after oseltamivir phosphate capsules administration, unless medically indicated. Inactivated Influenza Vaccine Inactivated influenza vaccine can be administered at any time relative to use of oseltamivir phosphate capsules. 7.2 Drugs Without Clinically Significant Drug Interaction with Oseltamivir Phosphate Capsules No dose adjustments are needed for either oseltamivir or the concomitant drug when coadministering oseltamivir with amoxicillin, acetaminophen, aspirin, cimetidine, antacids (magnesium and aluminum hydroxides and calcium carbonates), rimantadine, amantadine, or warfarin [see Clinical Pharmacology (12.3)] .
Use in specific groups
8.1 Pregnancy Risk Summary There are no adequate and well-controlled studies with oseltamivir phosphate capsules in pregnant women to inform a drug‐associated risk of adverse developmental outcomes. Available published epidemiological data suggest that oseltamivir phosphate capsule, taken in any trimester, is not associated with an increased risk of birth defects. However, these studies individually are limited by small sample sizes, use of different comparison groups, and some lacked information on dose, which preclude a definitive assessment of the risk [see Data and Clinical Pharmacology (12.3)] . In animal reproduction studies with oseltamivir, no adverse developmental effects were observed at clinically relevant exposures (see Data) . The background risk of major birth defects and miscarriage for the indicated populations is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage is 2 to 4% and 15 to 20%, respectively. Clinical Considerations Disease-Associated Maternal and/or Embryo/Fetal Risk Pregnant women are at higher risk of severe complications from influenza, which may lead to adverse pregnancy and/or fetal outcomes including maternal death, still births, birth defects, preterm delivery, low birth weight and small for gestational age. Data Human Data Published prospective and retrospective observational studies of more than 5,000 women exposed to oseltamivir phosphate capsules during pregnancy, including more than 1,000 women exposed in the first trimester, suggest that the observed rate of congenital malformations was not increased above the rate in the general comparison population, regardless of when therapy was administered during the gestational period. However, individually, none of these studies had adequate sample sizes and some lacked information on dose, which preclude a definitive assessment of the risk. […]
If too much is taken
Reports of overdoses with oseltamivir phosphate capsules have been received from clinical trials and during postmarketing experience. In the majority of cases reporting overdose, no adverse reactions were reported. Adverse reactions reported following overdose were similar in nature to those observed with therapeutic doses of oseltamivir phosphate capsules [see Adverse Reactions (6)] .
Before you take anything new
Tell your pharmacist or doctor about every medicine you take — including ones bought without a prescription, herbal products and supplements. Interactions are one of the most common avoidable causes of harm from medicines, and a pharmacist can check your full list in a couple of minutes.
This page is built from the openFDA record of the U.S. Food and Drug Administration's approved labelling for this product, effective 30 January 2023. Label text has been shortened and reformatted for readability; safety wording has not been altered in meaning. FDA labelling describes products approved in the United States — brand names, strengths, formulations and approved uses may differ in your country. Always read the leaflet that comes with your own pack. PocketsInfo is not affiliated with, and is not endorsed by, the FDA. Retrieved 2026-07-30.