Tamiflu, also known as oseltamivir phosphate, is an antiviral drug that is prescribed for the treatment and prevention of influenza A and B. It works by blocking an enzyme that influenza viruses need to spread inside the body. This helps reduce the duration and severity of flu symptoms. Tamiflu was developed by Gilead Sciences and first approved for medical use in 1999.

Tamiflu works by inhibiting an enzyme called neuraminidase that is located on the surface of influenza viruses. This enzyme helps the viruses to be released from infected cells so that they can spread throughout the respiratory tract and infect other cells. By blocking the action of neuraminidase, Tamiflu prevents the release of new viruses and thus slows the spread of influenza within the body. It does not kill the virus but interferes with its ability to infect new cells. This gives the immune system more time to build antibodies and fight off the viral infection.

Effectiveness against different flu strains

Clinical trials have shown that Tamiflu can reduce the duration of influenza symptoms by about 1 day when treatment is started within 48 hours of first onset of symptoms. It is considered effective against both influenza A and B viruses. However, its effectiveness may vary depending on the specific influenza virus strain causing illness in any given season. Tamiflu works best against influenza A viruses like H1N1 and H3N2 but may be less effective against some emerging novel influenza strains. Its ability to reduce complications from seasonal influenza has also been demonstrated in pediatric patients.

Dosage and administration

Tamiflu comes as capsules and oral suspension. For treatment of uncomplicated influenza, the recommended dosage is 75 mg twice daily for 5 days. For prevention of influenza following exposure, it is recommended at 75 mg once daily for 10 days. Treatment should begin within 2 days of onset of symptoms for maximum benefit. The capsules should be swallowed whole with water and should not be chewed or crushed. The oral suspension should be measured with an appropriate oral dosing syringe and mixed with a spoonful of sweetened food items before ingestion.

Safety and side effects

Tamiflu( oseltamivir phosphate) is generally well tolerated. Most common side effects reported are nausea, vomiting, headache and bronchitis. These side effects are usually mild to moderate in severity. Serious neuropsychiatric events like delirium and self-injury have also been reported in children and adolescents on Tamiflu therapy, especially with higher doses. As with all antiviral drugs, resistance to Tamiflu can potentially develop with inadequate or incomplete dosing. Due to this risk, it is important to take the full prescribed course of treatment even if symptoms improve earlier.

Special precautions and warnings

Tamiflu( oseltamivir phosphate) is not recommended during pregnancy unless clearly needed. It should also be used cautiously in patients with kidney disease. Live attenuated influenza vaccine (LAIV) should not be administered until 2 weeks after stoppage of Tamiflu therapy. Tamiflu does not treat symptoms that are not caused by influenza virus and is not a substitute for annual flu vaccination, which remains the most effective strategy for reducing influenza disease burden. Those at high-risk of complications from influenza like elderly, pregnant women or patients with chronic illnesses should consult a doctor at first signs of flu symptoms.

Role during influenza pandemics

In a pandemic situation where vaccine may not be available, antivirals like Tamiflu play an important role in reducing illness and transmission. When given as chemoprophylaxis, Tamiflu can reduce the risk of influenza in susceptible individuals exposed to the pandemic virus. It is stockpiled worldwide by many nations as part of their pandemic preparedness. During the 2009 H1N1 pandemic, Tamiflu was shown to be safe and well-tolerated for pediatric age groups when used for treatment and prevention of infection. Its strategic use can help curb and slow the virus spread in communities until a suitable vaccine becomes available.

Tamiflu( oseltamivir phosphate) remains an important first-line treatment for seasonal influenza A and B infections. When used appropriately within 48 hours of disease onset, it can reduce the duration and severity of symptoms. Its availability as an oral formulation also makes it convenient to administer. With increasing resistance to older antiviral drugs, Tamiflu continues to play a major role in antiviral stewardship practices. Besides chemo prophylaxis, it is also effective for post exposure prevention of influenza. At currently approved doses, Tamiflu is generally safe and well tolerated. However, close adherence to recommended dosage and treatment duration is important to minimize resistance issues. Further research continues for new improved antiviral agents against emerging influenza strains.