How to use oseltamivir, the "miracle drug" for influenza A, correctly?

Recently, influenza A virus infection has spread in many places in my country. Children, pregnant women and the elderly are all at high risk of influenza, causing the anti-influenza drug oseltamivir to become a hot topic again. So, is oseltamivir really a "magic drug"? Do you really know how to use it correctly?

What kind of drug is oseltamivir?

Although both the common cold and influenza are acute respiratory diseases, the common cold is most commonly caused by rhinovirus or coronavirus; influenza is caused by influenza A or B virus, and occasionally by influenza C virus. Oseltamivir is an antiviral drug - a neuraminidase inhibitor. It can prevent the release of virions from host cells and has anti-influenza A and B virus effects.

How to use oseltamivir?

Once influenza patients become ill, they should start taking oseltamivir as soon as possible, ideally within 48 hours of symptom onset; when oseltamivir is used for prevention, it should also be taken within 48 hours of contact with influenza patients.

Oseltamivir can be used to treat influenza A and B in adults and children aged ≥1 year, and to prevent influenza A and B in adults and adolescents aged ≥13 years. In 2012, the U.S. Food and Drug Administration (FDA) specially approved its use in babies over 14 days old. The benefits of using oseltamivir for pregnant and breastfeeding patients outweigh the risks of influenza complications.

What are the main adverse reactions of oseltamivir ?

Oseltamivir has good overall safety. The most common adverse reactions are nausea, vomiting, and abdominal pain. Rashes and nosebleeds are rare. Occasionally, there are adverse reactions of the nervous system, such as delusions, hallucinations, and delirium. Adverse reactions of the nervous system often occur in children aged 16 and under, and the frequency of males is higher. Adverse reactions of the nervous system generally occur within 48 hours of starting treatment. Parents are advised to closely observe whether their children have abnormal behavior after taking oseltamivir.

Which groups of people can use oseltamivir as a preventive medication for influenza?

The following key groups who have a history of close contact with influenza patients may consider using oseltamivir to prevent influenza:

1. People at high risk of severe illness who have not been vaccinated or have not acquired stable immunity after influenza vaccination (within 2 weeks of vaccination) (such as pregnant women or women 4 weeks postpartum, cancer patients, people with suppressed or defective immune function, obese patients, people aged 65 and above, and patients with underlying diseases such as kidney disease, liver disease, respiratory system disease, cardiovascular system disease, and blood system disease).

2. Health care workers or medical staff who have close contact with people at high risk of severe illness.

3. People with severe immunodeficiency who have difficulty obtaining effective immunity after vaccination.

4. Extremely high-risk groups such as organ transplant patients can take precautions in advance during the influenza outbreak season.

What are the precautions for using oseltamivir?

1. Food does not affect the efficacy of the medicine. If stomach discomfort occurs after taking the medicine, the medicine can be taken with food.

2. Oseltamivir can inhibit the replication of live attenuated influenza vaccine viruses, thereby weakening the efficacy of the vaccine. Live attenuated influenza vaccines should be avoided within the first 2 weeks of starting oseltamivir or within 48 hours after stopping this drug. There is no time limit for inactivated influenza vaccines and they are not affected by oseltamivir.

3. Oseltamivir capsules are ineffective against diseases caused by pathogens other than influenza virus. Patients should be alert to the possibility of secondary bacterial infection and receive appropriate treatment.

4. Oseltamivir only prevents influenza during the period of use and cannot replace influenza vaccine.

References:

[1] National Clinical Research Center for Respiratory Diseases, Chinese Medical Association Pediatrics Branch Respiratory Group. Expert consensus on diagnosis and treatment of influenza in children (2020 edition) [J]. Chinese Journal of Practical Pediatrics, 2020, 35(17): 1281-1288.

[2] Oseltamivir Phosphate Capsules Drug Instructions, National Medicine Standard No. H20065415. Modification date: July 29, 2021.

[3] Chinese Medical Doctor Association Emergency Physician Branch, Chinese Medical Association Emergency Medicine Branch, China Emergency Medical Association, etc. Emergency Expert Consensus on Diagnosis and Treatment Standards for Adult Influenza (2022 Edition)[J]. Chinese Journal of Emergency Medicine, 2022, 42(12): 1013-1026.