This page contains brief details about the drug , it's indication, dosage & administaration, mechanism of action, related brands with strength, warnings and common side effects.

Background and Date of Approval

Oseltamivir Phosphate is an anti-viral medication that belongs to neuraminidase inhibitor and was approved by the FDA on December 14, 2000, for the treatment and prevention of influenza A and B. 

Mechanism of Action of undefined

Oseltamivir Phosphate is a pro-drug that gets converted into its active form (Oseltamivir carboxylate) inside the body. It is a neuraminidase inhibitor used in the treatment and prophylaxis of influenza. It works by inhibiting the neuraminidase enzyme present on the surface of the virus. This enzyme is essential for the virus to enter the healthy cells and release newly formed virus particles from infected cells, thereby spreading the infectious virus throughout the body.  Oseltamivir Phosphate reduces viral shedding and infectivity. 

Uses of undefined

Oseltamivir Phosphate is used to treat Influenza A and B in patients two weeks of age and older who do not have symptoms for more than 2 days. It also prevents influenza type A and B in patients 1 year and older.

undefined Drug administaration and Dosage available

Oseltamivir Phosphate is a prescription drug available as an oral capsule and suspension. The dosage form, dose, and frequency of administration will be decided by your doctor based on your disease condition and other factors. Take medicine as directed by your physician. Take it with or without food. The chances of stomach upset are less if you take this medicine with food. If you are prescribed a capsule, swallow the capsule as a whole with water. Do not break, chew or crush the capsule.

Oral suspension is prescribed when the patient cannot swallow the tablet form of this medicine. Shake the suspension well before every use. The recommended dose is based on the individual’s body weight. It is important to complete the whole course, even if you start to feel better quickly.

Warnings, Precautions and Side Effects of undefined


This medication tends to cause severe allergic reactions. Do not take this medicine if you are allergic to oseltamivir phosphate or any other ingredients in it. Report to your doctor if you note or suspect any allergic-like reactions. This medication may cause neuropsychiatric events such as confusion or abnormal behavior especially in the pediatric population. Regular monitoring of behavioral signs is necessary. This medication may not prevent any bacterial infection that co-exist with influenza.


Inform your physician about all the prescription medicines, over-the-counter medicines, nutritional or vitamin supplements, nasal flu vaccine, and herbal products that you are currently taking or have taken before.  Inform your physician if you have or ever had liver disease, fever or infection, kidney problems, heart problems, or kidney disorder before starting the treatment with this medicine. Notify your physician if you have any hereditary sugar intolerance. It is unsafe to take this medicine during breastfeeding. Inform your physician if you are pregnant, breastfeeding, or planning to become pregnant.

Side Effects

Some common side effects of Oseltamivir Phosphate are nausea, vomiting, ear infection, headache, bronchitis and cough, dizziness, and sleeping difficulties. Serious side effects are stevens-johnson syndrome, swelling in the face and skin, itchy rashes, low blood pressure, breathing difficulty, abnormal behavior and changes in mood, GI bleeding, abnormal or irregular heart beat, and inflammation of the liver. 

Word Of Advice

This medication is not a substitute for any flu vaccination. Inform your physician if you are experiencing any symptoms of swelling in the face, feet, hands, and abdomen, difficulty in breathing, sudden drop in blood pressure, abdominal pain, weakness, and skin rashes. Store the oral capsules at 25 °C. Shake the oral suspension before every use. Do not store the oral suspension above 30°C. After reconstitution, store below 25 °C for 10 days. If the oral suspension is refrigerated, it should be consumed within 17 days. 

Frequently Asked Question


  1. (2022). Oseltamivir Phosphate powder for oral suspension. Available at:  [Accessed 24 Feb. 2023].
  2. HIGHLIGHTS OF PRESCRIBING INFORMATION. (2012). Available at: [Accessed 24 Feb. 2023].
  3. (n.d.). Tamiflu (oseltamivir) dosing, indications, interactions, adverse effects, and more. Available at:  [Accessed 24 Feb. 2023].


The drug information on this page is not a substitute for medical advice. It is meant for educational purposes only. For further details, consult your doctor about your medical condition to know if you can receive this treatment.