Description

Simple

A medication used to treat and prevent influenza.

Clinical

A neuraminidase inhibitor used in the prophylaxis and treatment of influenza.

Overview

Oseltamivir (marketed as the product TamifluⓇ), is an antiviral neuraminidase inhibitor used for the treatment and prophylaxis of infection with influenza viruses A (including pandemic H1N1) and B. Oseltamivir exerts its antiviral activity by inhibiting the activity of the viral neuraminidase enzyme found on the surface of the virus, which prevents budding from the host cell, viral replication, and infectivity.

The clinical benefit of use of oseltamivir is greatest when administered within 48 hours of the onset of influenza symptoms since effectiveness decreases significantly after that point in time; there is generally no benefit in use beyond 48 hours for healthy, low-risk individuals as influenza is a self-limiting illness.[10, 19, Read more

Pharmacology

Indication

According to FDA prescribing information, oseltamivir is 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 [ Read more

Pharmacodynamic

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. Because these events were reported voluntarily during clinical practice, estimates of frequency cannot... Read more

Mechanism of action

Oseltamivir phosphate is a pro-drug of the active metabolite (oseltamivir carboxylate) which is a potent and selective inhibitor of influenza virus neuraminidase enzymes, which are glycoproteins found on the virion surface. Viral neuraminidase enzyme activity is important for viral entry into uninfe... Read more

Absorption

Oseltamivir is readily absorbed from the gastrointestinal tract after oral administration of oseltamivir phosphate and is extensively converted by predominantly hepatic esterases to the active metabolite oseltamivir carboxylate. At least 75 % of an oral dose reaches the systemic circulation as the a... Read more

Protein binding

The binding of the active oseltamivir carboxylate metabolite to human plasma protein is negligible at approximately 3 % while the binding of oseltamivir to human plasma protein is 42%, which is insufficient to cause significant displacement-based drug interactions.[ Read more

Volume of distribution

The mean volume of distribution at steady state of the oseltamivir carboxylate ranges approximately between 23 and 26 liters in humans, a volume that is roughly equivalent to extracellular body fluid. Since neuraminidase activity is extracellular, oseltamivir carboxylate distributes to all sites of... Read more

Clearance

Renal clearance (18.8 l/h) of the drug exceeds glomerular filtration rate (7.5 l/h) indicating that tubular secretion occurs in addition to glomerular filtration.[21]

Half life

Plasma concentrations of oseltamivir declined with a half-life of 1 to 3 hours in most subjects after oral administration, although plasma concentrations of oseltamivir carboxylate declined with a half-life of 6 to 10 hours in most subjects after oral administration.[ Read more

Route of elimination

Following absorption, oseltamivir is more than 90 % eliminated through conversion to oseltamivir carboxylate and subsequent elimination entirely through renal excretion. During clinical studies, less than 20 % of oral radiolabelled dose was found to be eliminated in faeces.[ Read more

Toxicity

Reports of overdoses with oseltamivir 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... Read more

Adverse Effects

Effect Regions Age Groups Incidences Evidence Type
Headache US
  • Kind: experimental
    • Percent: 2-17%
  • Kind: placebo
    • Percent: 1-16%
  • Clinical Trial
    Headache US
  • Kind: experimental
    • Percent: 2-17%
  • Kind: placebo
    • Percent: 1-16%
  • Clinical Trial
    Vomiting US
  • Kind: experimental
    • Percent: 2-16%
  • Kind: placebo
    • Percent: 1-3%
  • Clinical Trial
    Nausea US
    • adolescent
    • adult
  • Kind: experimental
    • Percent: 8-10%
  • Kind: placebo
    • Percent: 4-6%
  • Clinical Trial
    Diarrhea US
    • pediatric
  • Kind: experimental
    • Percent: 7%
  • Clinical Trial
    Diaper Rash US
    • pediatric
  • Kind: experimental
    • Percent: 7%
  • Clinical Trial
    Pain US
  • Kind: experimental
    • Percent: 1-4%
  • Kind: placebo
    • Percent: 1-3%
  • Clinical Trial
    Pain US
  • Kind: experimental
    • Percent: 1-4%
  • Kind: placebo
    • Percent: 1-3%
  • Clinical Trial
    Allergy US
    Post Marketing
    Anaphylactic/anaphylactoid reactions US
    Post Marketing
    Swelling of the face or tongue US
    Post Marketing
    Stevens-Johnson Syndrome US
    Post Marketing
    Erythema multiforme US
    Post Marketing
    Eczema US
    Post Marketing
    Toxic Epidermal Necrolysis US
    Post Marketing
    Dermatitis US
    Post Marketing
    Urticaria US
    Post Marketing
    Hypothermia US
    Post Marketing
    Rash US
    Post Marketing
    Aggravation of diabetes US
    Post Marketing
    Abnormal behaviour US
    Post Marketing
    Abnormal Liver Function Tests US
    Post Marketing
    Seizure US
    Post Marketing
    Arrhythmia US
    Post Marketing
    Hepatitis US
    Post Marketing
    Gastrointestinal Bleeding US
    Post Marketing
    Hemorrhagic Colitis US
    Post Marketing
    Delusions US
    Post Marketing
    Nightmares US
    Post Marketing
    Confusion US
    Post Marketing
    Altered LOC US
    Post Marketing
    Anxiety US
    Post Marketing
    Agitation US
    Post Marketing
    Hallucinations US
    Post Marketing
    Delirium US
    Post Marketing

    Contraindications

    Information currently not available.

    Food Interactions

    Take with or without food. Co-administration with food does not affect pharmacokinetics but may enhance tolerability.