Action and Spectrum

Actions and Spectrum: 

• Inhibition of neuraminidase: oseltamivir works by inhibiting the activity of neuraminidase, an enzyme that is required by the influenza virus to spread from infected cells to uninfected cells.  
• Spectrum of activity: oseltamivir is active against both influenza A and B viruses, including strains that are resistant to other antiviral medications. It is also effective against avian influenza (bird flu) and swine flu. 
• Treatment of influenza: oseltamivir is typically used to treat people who have symptoms of influenza and who have been diagnosed with the virus. It can reduce the severity and duration of symptoms, as well as the risk of complications such as pneumonia. 
• Prevention of influenza: oseltamivir can also be used to prevent influenza in people who have been exposed to the virus, such as in the case of an influenza outbreak or in people who are at high risk of complications from the virus. 
• Timing of administration: oseltamivir is most effective when it is started within 48 hours of the onset of symptoms. After this time, its effectiveness is reduced. 

Drug Interaction

Adverse Reaction

1-10%: 

Epistaxis 

Vertigo 

Ear disorder 

Abdominal pain 

Conjunctivitis 

<1%: 

Aggravation of diabetes 

Arrhythmia 

Anemia 

Delirium 

Confusion 

Hemorrhagic & Pseudomembranous colitis 

Increase transaminases  

Unstable angina 

Face swelling  

Colitis 

Pyrexia 

Peritonsillar abscess 

Rash 

Seizure 

Hepatitis 

Humerus fracture 

Black Box Warning

Black Box Warning: 

The black box warning for oseltamivir is related to neuropsychiatric events. The U.S. Food and Drug Administration (FDA) requires a black box warning on the package insert for oseltamivir, indicating that it may cause neuropsychiatric events, such as delirium, hallucinations, and abnormal behavior, particularly in children and adolescents. 

Contraindication / Caution

Contraindication / Caution: 

• Allergy: Individuals who are allergic to oseltamivir or any of its ingredients should not take this medication. 
• Kidney Disease: oseltamivir is primarily eliminated from the body through the kidneys. Therefore, individuals with severe kidney disease may require a dosage adjustment or may not be able to take this medication. 
• Pregnancy and breastfeeding: The safety of oseltamivir in pregnant and breastfeeding women has not been fully established, and it should only be used if the potential benefits outweigh the risks. 
• Liver disease: oseltamivir is metabolized in the liver, and individuals with severe liver disease may require a dosage adjustment or may not be able to take this medication. 
• Respiratory disease: oseltamivir may cause bronchospasm in individuals with respiratory disease, so caution should be exercised in such cases. 
• Psychiatric conditions: oseltamivir may cause neuropsychiatric events such as hallucinations, delirium, and abnormal behavior in some individuals, especially children. Therefore, patients with a history of psychiatric disorders should be closely monitored. 
• Interaction with other medications: oseltamivir may interact with other medications, such as probenecid, which can increase the concentration of oseltamivir in the body. Therefore, individuals taking other medications should inform their healthcare provider before taking oseltamivir. 

Pregnancy / Lactation

Pregnancy consideration:  

The drug is not indicated during pregnancy. 

Breastfeeding warnings:  

The benefits of breastfeeding and the effects of the drug should be considered if administering the drug. 

Pregnancy category: 

• Category A: Satisfactory and well-controlled studies show no risk to the fetus in the first or later trimester. 
• Category B: No evidence shows the risk to the fetus found in animal reproduction studies, and there are not enough studies on pregnant women.    
• Category C: Adverse effects on the fetus found with evidence in animal reproduction studies and no adequate evidence for a product in humans; Pregnant women must take care of the potential risks. 
• Category D: There is adequate data available with sufficient evidence of human fetal risk from various platforms. However, despite potential dangers may be used only in emergency cases for potential benefits. 
• Category X: Drugs listed in this category outweigh the risks over the benefits. The drug is not for pregnant women. 
• Category N: No data is available for the drug under this category. 

Pharmacology

Pharmacology: 

oseltamivir is an antiviral medication that is used to treat and prevent influenza virus infections.  

Pharmacodynamics: 

It works by inhibiting the neuraminidase enzyme of the influenza virus, which prevents the release of newly formed viral particles from infected cells. 

Pharmacokinetics: 

Absorption 

oseltamivir is administered orally as an inactive prodrug, oseltamivir phosphate. It is rapidly absorbed from the gastrointestinal tract and converted into its active form, oseltamivir carboxylate, by hepatic esterases.  

Distribution 

oseltamivir carboxylate has a volume of distribution of about 23 liters, indicating that it is widely distributed throughout the body. The drug is highly protein-bound (>99%) and primarily distributed to the respiratory tract. 

Metabolism 

oseltamivir is primarily metabolized in the liver to its active metabolite, oseltamivir carboxylate, by esterases. The drug is not a substrate for cytochrome P450 enzymes. 

Elimination and Excretion 

oseltamivir carboxylate is primarily eliminated unchanged in the urine through glomerular filtration and active tubular secretion. The elimination half-life of oseltamivir carboxylate is approximately 6 to 10 hours in healthy adults. 

Adminstartion

Administration: 

oseltamivir is an antiviral medication that is used to treat and prevent influenza A and B infections. It is generally administered orally in the form of a capsule or liquid suspension. 

The dosage and duration of treatment may vary depending on the age and condition of the patient. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: oseltamivir 

Pronounced: oh-sayl-taa-mi-vir 

Why do we use oseltamivir? 

oseltamivir is primarily used to treat and prevent influenza A and B infections. It is not typically used as a first-line treatment for viral pneumonia in children because viral pneumonia can be caused by many different viruses, and oseltamivir is only effective against influenza viruses. 

However, in some cases, viral pneumonia may be caused by an influenza virus, and oseltamivir may be prescribed to treat the infection. This is because oseltamivir can help to reduce the severity and duration of influenza symptoms, which can include coughing, fever, and respiratory distress. 

It is important to note that oseltamivir is most effective when it is started within 48 hours of the onset of influenza symptoms, so it is important to seek medical attention promptly if you suspect that your child may have influenza or viral pneumonia.