Health Tips

Viral infection seems to be the hot topic nowadays. 

Hence, today we bring you an article on an antiviral medication known as oseltamivir.

Function of oseltamivir

Image via DG Hisham 

Oseltamivir, commonly goes by its brand name Tamiflu^®, is a medication that is used to treat or prevent influenza virus — the virus that causes flu. After you take oseltamivir, your body converts it into its activated form known as oseltamivir carboxylate. Oseltamivir carboxylate inhibits influenza virus neuraminidase, an enzyme known to help influenza viruses release their own ‘copies’. In other words, oseltamivir reduces the multiplication of influenza virus. 

Oseltamivir is used to prevent flu in patients one year and older and treat uncomplicated illness due to flu virus infection in patients more than 2 weeks of age who have shown symptoms for no more than 48 hours. For more complicated viral infection cases, other antivirals may be considered. This medicine may also be used to prevent becoming infected with the flu virus after being potentially exposed to it. 

Nevertheless, if you would like to prevent yourself from getting influenza virus just for general safety sake, influenza vaccine is a more appropriate choice.

A person receives the seasonal influenza vaccine (flu shot). Credit: National Institute of Allergy and Infectious Diseases, NIH

Fun fact: When the then SARS-CoV-2 virus first emerged in Wuhan, China, there was a 'tiny craze' for oseltamivir in Malaysia. The general public back then thought it was a mystery flu and wanted to get their hands on Tamiflu to prevent the disease.

How should you take this medicine?

The doses of oseltamivir may vary depending on whether it is used to treat or prevent influenza virus, as well as the patient’s age, body weight and kidney function. You should take oseltamivir exactly as directed by your doctor. Do not take more or less than instructed by your doctor.

Oseltamivir are available in two forms: (Source: FUKKM)

1. Oral liquid suspension (strength: 60mg/5ml) - Shake the bottle well before you take it to ensure that the liquid is evenly mixed. Use the measuring spoon or cup provided to measure your prescribed dose. Your doctor will advise you on the treatment regimen depending on your condition, response and tolerability to this medicine. This liquid suspension contains sorbitol and may lead to upset stomach and diarrhea in people who have fructose intolerance.

2. Capsule (75mg) - Swallow it whole with water. Do not chew or crush the capsule. If you have difficulty swallowing, the capsule may be opened and mixed with sweetened food products such as chocolate syrup, sweetened condensed milk, apple sauce, or yogurt. A liquid suspension can also be made from the capsules if needed.

Side effects of oseltamivir

All medications may cause side effects. However, many people have no side effects or only have minor side effects with oseltamivir. Some common ones are:

• Diarrhea, upset stomach, or throwing up.

• Headache

Some side effects may need immediate medical help. Alert your doctor quickly if you experience any of the following:

• swelling of the mouth, face, lips, tongue, or throat

• skin rashes leading to blisters, peeling, and shedding of large skin areas

• unusual changes in mood or behaviour (being too depressed, agitated, or having compulsive and impulsive behaviour)

• confusion, hallucinations (seeing or hearing things that are non-existent), thoughts of self-harm

These are extremely rare but serious side effects. Inform your doctor if any of these side effects do not go away or are severe, or if you experience other side effects.

What if I’ve forgotten to take this medicine?

Take the missed dose as soon as you remember. If it is less than 2 hours before the next dose is due, skip the missed dose and return to your normal dosing schedule. DO NOT double a dose under any circumstances. If you often forget to take your medicine, let your doctor and pharmacist know.

Important takeaway about oseltamivir

• Before taking oseltamivir, inform your doctor about any allergies to any substances and if you have kidney disease.

• Tell your doctor and pharmacist about all of your medications (prescription or over-the-counter, herbal products, vitamins) and health problems. You must check to make sure that it is safe for you to take oseltamivir with all of your medications and health problems. Do not start, stop, or change the dose of any medication without checking with your doctor. Oseltamivir may also interact with certain medications, hence it’s best you check with a healthcare professional.

• You should continue taking the medication for the duration recommended by the doctor, even after you feel better. It’s crucial that you complete the entire course of medicine.

• You may take this medicine with or without food, but try to take it at the same time each day.

• Oseltamivir is NOT used for the treatment of common colds.

• Oseltamivir helps to relieve flu symptoms, but it does not stop the spread of the flu to others. If you have the flu, it’s important that you rest at home or limit outdoor activities, wash hands regularly and wear a mask when going out. 

• Talk with your doctor before getting a flu vaccine after taking oseltamivir. Talk with your doctor before you take oseltamivir if you have just gotten a flu vaccine.

• Tell your doctor if you are pregnant, plan on getting pregnant, or are breast-feeding. You will need to talk about the benefits and risks to you and the baby.

3-D illustration of a flu virus. Credit: National Institute of Allergy and Infectious Diseases, National Institutes of Health

A word from Doc2Us

If you have any questions related to flu, you can consult our professional doctors and healthcare professionals on Doc2Us. Doc2Us is a mobile application that allows you to talk to a doctor or any healthcare professionals via text chat at any time and from anywhere. For better communication, you can even send our online doctor images or voice messages related to your medical inquiry.

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Disclaimer: As a service to our users and general public, Doc2Us provides health education contents. Please note the date of last review or update on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

References

1. UpToDate - Oseltamivir: Drug information

2. MIMS - Oseltamivir 

Cover image credit: National Institute of Allergy and Infectious Diseases, National Institutes of Health

Written by

Ms Joyce Toh