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Oseltamivir

AEMPS

Neuraminidase inhibitors

ATC code: J05AH02

Updated · Methodology

Indications

A

Influenza

First line

First-line antiviral for influenza in adults and children. RCTs show that starting treatment within 48 hours of symptom onset shortens illness by 1–2 days and reduces complication risk. In hospitalized patients and high-risk groups – pregnant, elderly, immunocompromised – treatment is started even beyond 48 hours.

Sources

  1. IDSA: Clinical practice guidelines by the Infectious Diseases Society of America: 2018 update on diagnosis, treatment, chemoprophylaxis and institutional outbreak management of seasonal influenza (2018)
  2. EMA: Tamiflu (oseltamivir) – European public assessment report (EPAR) (2002)
  3. Cochrane Database of Systematic Reviews: Neuraminidase inhibitors for preventing and treating influenza in adults and children (2014)
  4. The Lancet: Oseltamivir treatment for influenza in adults: a meta-analysis of randomised controlled trials (2015)

ICD-10: J10-J11 · ICD-11: 1E32

Marketing claims without evidence base

The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.

F

COVID-19

Not recommended

Not effective against COVID-19. Oseltamivir inhibits neuraminidase, which SARS-CoV-2 lacks. The virus uses spike protein and ACE2 receptor for cell entry – an entirely different mechanism. Early oseltamivir prescriptions during COVID were driven by diagnostic uncertainty when influenza had not been ruled out.

Sources

  1. PLoS One: Systematic review and meta-analysis of the efficacy and safety of oseltamivir (Tamiflu) in the treatment of Coronavirus Disease 2019 (COVID-19). (2022)
  2. Bioorg Chem: Is oseltamivir suitable for fighting against COVID-19: In silico assessment, in vitro and retrospective study. (2020)

ICD-10: U07.1 · ICD-11: RA01.0

How to read tiers A–F
  • AStrong evidence – first or second line in international guidelines
  • BRecommended in selected cases
  • CStudy data contradict each other
  • DBenefit not proven, no documented harm
  • FDocumented harm, or risk without benefit

Mechanism of action

Prodrug. Converted in the liver to oseltamivir carboxylate, which selectively inhibits influenza A and B neuraminidase. Neuraminidase cleaves sialic acid residues on infected cell surfaces, and without it viral particles cannot bud off. The drug blocks this step and reduces viral spread.

Safety

Contraindications

  • Hypersensitivity to oseltamivir

Serious adverse effects

  • Neuropsychiatric events in adolescents – delirium, abnormal behavior, hallucinations (rare, predominantly in Japanese cohorts)
  • Anaphylaxis and severe skin reactions (Stevens-Johnson syndrome – isolated cases)

Common adverse effects

  • Nausea
  • Vomiting
  • Headache

Pregnancy: can you take Oseltamivir?

EMA summary of product characteristics (section 4.6): influenza is associated with adverse pregnancy and fetal outcomes, including a risk of major congenital malformations such as congenital heart defects. A large amount of post-authorisation and observational data (outcomes of more than 1,000 first-trimester exposures) indicates that oseltamivir causes no malformations and no fetal or neonatal toxicity. In one observational study the overall malformation risk was not increased, but results for major congenital heart defects diagnosed within 12 months of birth were inconclusive: 1.76% (7 newborns out of 397 pregnancies) after first-trimester exposure versus 1.01% in unexposed pregnancies in the general population (odds ratio 1.75, 95% CI 0.51 to 5.98), and the study had limited power. Animal studies have not shown reproductive toxicity. Oseltamivir may be considered in pregnancy if needed, taking into account the available safety and benefit data and the pathogenicity of the circulating influenza strain.

Breastfeeding: can you take Oseltamivir?

Compatible. Hale L2. Minimal transfer into milk (RID about 0.5%); plasma concentrations in the infant remain subtherapeutic. WHO, AEMPS and AAP consider it compatible with breastfeeding; influenza treatment in a nursing mother does not require interruption. Mild diarrhoea or nausea in the infant may occur and usually resolves without intervention.

Calculate RIDFull profile on NIH LactMed ↗

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Practical notes

Timing and administration

Take twice daily for 5 days. Taking with food reduces nausea but does not affect bioavailability. Start as early as possible – ideally within 48 hours. In children, the dose is weight-based. For post-exposure prophylaxis – 75 mg once daily for 10 days.

Common myths

Myth: 'oseltamivir doesn't work, Cochrane proved it'. Fact: the 2014 Cochrane review did find limited impact on complications, but the original RCTs were not powered for that endpoint. Meta-analyses of observational data show reduced mortality in hospitalized patients. CDC, , and still recommend oseltamivir for influenza treatment.
Label mentions10 mentions

Verbatim lines from the interaction sections, in the language of the label

From this drug’s label

  • ModerateMethotrexate
    «Eliminación renal: Las interacciones medicamentosas clínicamente importantes basadas en una competición por la secreción tubular renal son poco probables, dado el margen de seguridad conocido de la…»

    AEMPS, section 4.5 · Open on CIMA

  • Acetylsalicylic acid
    «Información adicional: No se han observado interacciones farmacocinéticas entre oseltamivir o su principal metabolito cuando oseltamivir se administra conjuntamente con paracetamol, ácido…»

    AEMPS, section 4.5 · Open on CIMA

  • Amoxicillin
    «Amoxicilina: Oseltamivir no presenta ninguna interacción cinética con amoxicilina, que se elimina a través de la misma vía, lo que sugiere que la interacción de oseltamivir con esta vía es limitada.»

    AEMPS, section 4.5 · Open on CIMA

  • Amoxicillin
    «Drugs Without Clinically Significant Drug Interaction with Oseltamivir Phosphate Capsules: No dose adjustments are needed for either oseltamivir or the concomitant drug when coadministering…»

    FDA, section 7 · Open on DailyMed

  • antacidsclass named in the label
    «Drugs Without Clinically Significant Drug Interaction with Oseltamivir Phosphate Capsules: No dose adjustments are needed for either oseltamivir or the concomitant drug when coadministering…»

    FDA, section 7 · Open on DailyMed

  • antiácidosclass named in the label
    «Información adicional: No se han observado interacciones farmacocinéticas entre oseltamivir o su principal metabolito cuando oseltamivir se administra conjuntamente con paracetamol, ácido…»

    AEMPS, section 4.5 · Open on CIMA

  • Inactivated influenza vaccine
    «Influenza Vaccines: Inactivated Influenza Vaccine»

    FDA, section 7 · Open on DailyMed

  • Paracetamol
    «Información adicional: No se han observado interacciones farmacocinéticas entre oseltamivir o su principal metabolito cuando oseltamivir se administra conjuntamente con paracetamol, ácido…»

    AEMPS, section 4.5 · Open on CIMA

  • Warfarin
    «Información adicional: No se han observado interacciones farmacocinéticas entre oseltamivir o su principal metabolito cuando oseltamivir se administra conjuntamente con paracetamol, ácido…»

    AEMPS, section 4.5 · Open on CIMA

  • Warfarin
    «Drugs Without Clinically Significant Drug Interaction with Oseltamivir Phosphate Capsules: No dose adjustments are needed for either oseltamivir or the concomitant drug when coadministering…»

    FDA, section 7 · Open on DailyMed

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Frequently asked

What is Oseltamivir used for?

Oseltamivir is evaluated for the following indications with varying evidence strength: Influenza (evidence tier A), COVID-19 (evidence tier F). See the full indication matrix with dosing and citations above on this page.

What are the side effects of Oseltamivir?

Common side effects of Oseltamivir (≥ 1 in 100): Nausea, Vomiting, Headache. See the Safety section for uncommon and serious reactions.

Is Oseltamivir safe during pregnancy?

EMA summary of product characteristics (section 4.6): influenza is associated with adverse pregnancy and fetal outcomes, including a risk of major congenital malformations such as congenital heart defects. A large amount of post-authorisation and observational data (outcomes of more than 1,000 first-trimester exposures) indicates that oseltamivir causes no malformations and no fetal or neonatal toxicity. In one observational study the overall malformation risk was not increased, but results for major congenital heart defects diagnosed within 12 months of birth were inconclusive: 1.76% (7 newborns out of 397 pregnancies) after first-trimester exposure versus 1.01% in unexposed pregnancies in the general population (odds ratio 1.75, 95% CI 0.51 to 5.98), and the study had limited power. Animal studies have not shown reproductive toxicity. Oseltamivir may be considered in pregnancy if needed, taking into account the available safety and benefit data and the pathogenicity of the circulating influenza strain.

Is Oseltamivir compatible with breastfeeding?

Compatible. Hale L2. Minimal transfer into milk (RID about 0.5%); plasma concentrations in the infant remain subtherapeutic. WHO, AEMPS and AAP consider it compatible with breastfeeding; influenza treatment in a nursing mother does not require interruption. Mild diarrhoea or nausea in the infant may occur and usually resolves without intervention.

Who should not take Oseltamivir?

Oseltamivir is contraindicated in: Hypersensitivity to oseltamivir. Full list in the Safety section.

oseltamivir doesn't work, Cochrane proved it

the 2014 Cochrane review did find limited impact on complications, but the original RCTs were not powered for that endpoint. Meta-analyses of observational data show reduced mortality in hospitalized patients. CDC, IDSA, and WHO still recommend oseltamivir for influenza treatment.

Official sources

Direct links to regulator labels. Open in a new tab.

Other drugs in this group

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