What is Oseltamivir?

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With the current pandemic of COVID-19, the problem of influenza or the ‘flu’ has taken a back seat. Over the past few years though,  ‘flu season’ has been an ongoing health concern. Fortunately, flu shots or vaccinations against the seasonal flu are available and recommended for most individuals to protect themselves during flu season. Many employers in the United States require getting a flu shot at the onset of flu season. 

What is the seasonal flu? The flu is a contagious infection caused by the Influenza virus group. The flu season usually starts in October with its peak between December and February. Sometimes, depending on the season, it can remain a problem as late as into May. The number of Influenza cases that cause illness, result in hospitalizations, and lead to deaths can vary every year depending on several factors like how many people actually get vaccinated against the flu for that season, what characteristics the virus has for that season, and what time during the flu season it is. The Centers for Disease Control and Prevention (CDC) estimates that since 2010, Influenza causes anywhere between 9 million to 45 million cases of illness, between 140,000 to 810,000 hospitalizations, and between 12,000 to 61,000 deaths every year. These numbers are alarmingly high despite the availability of a vaccination and awareness of how the illness can spread. 

Infection by the influenza virus can spread through droplet infection. When infected people cough or sneeze, they spray small droplets that when inhaled by an uninfected individual can transmit the virus to them. This can occur from even six feet away. According to the CDC, people with the flu are usually the most contagious within the first three days of showing symptoms, but they can also transmit the virus to other people one day before they begin to have symptoms. Typical symptoms of the flu include fever, cough, sore throat, body ache and fatigue. Often, many people have only mild symptoms and can get better with home treatment of rest and over-the-counter medications to reduce fever and pain. Individuals who belong to high-risk categories, like being in the age group above 65, young children, or pregnant women may need to seek medical care. Anti-viral drugs that target the influenza virus are usually prescribed in these cases and to otherwise healthy individuals that may experience severe symptoms. One of the major drugs that is prescribed for an Influenza infection is oseltamivir, also known as the brand name Tamiflu. 

How does Oseltamivir work? 

Influenza Type A and Type B viruses cause the flu. These viruses can infect human cells through an enzyme called neuraminidase. This enzyme cleaves a component, named sialic acid that is found on proteins that are on the surface of human cells. Normally, the Influenza virus replicates inside human cells and uses the neuraminidase to allow newly replicated virions to exit the cell. What is Oseltamivir used for? Oseltamivir inhibits neuraminidase by binding to it and preventing it from cleaving the sialic acid on human cells. This prevents viral replication from occurring and propagating itself within the body. Not all viruses have neuraminidase, so this drug selectively works on the Influenza Type A and Type B viruses. 

Discovery of Oseltamivir 

Oseltamivir, known as the brand Tamiflu, was discovered by scientists at Gilead Sciences, who sold their patent to the pharmaceutical giant, La-Hoffman-Roche in 1996. Since then, Tamiflu is manufactured and marketed by Roche. The active ingredient of the drug was originally derived from the Star Anise plant. Shikimic acid, isolated from Star Anise, was the original source of the neuraminidase inhibitor. The Food and Drug Administration (FDA) approved the use of oseltamivir to treat influenza in 1999. Later in 2002, the drug was also approved for use to treat the flu by the European Medicines Authority (EMA). During the Avian Flu pandemic in 2005 caused by the influenza virus H5N1, oseltamivir was stockpiled by many countries including the United States, the United Kingdom, and Australia in order to prepare for the pandemic. Again in 2009, during the Swine Flu pandemic caused by the influenza virus H1N1 that was spreading through North America, oseltamivir was recommended for use by the World Health Organization (WHO) and the CDC. 

How effective is Oseltamivir? 

The benefits of taking oseltamivir to treat the flu have been controversial. The drug, marketed by Roche as Tamiflu, has gone through a rocky history of whether it is deemed effective enough for use to treat the flu. Initial clinical trials conducted by Roche concluded that the drug was safe and effective for reducing the number of hospitalizations and occurrence of secondary infections due to Influenza infection. Due to the perceived success of these early trials, the FDA and the EMA approved it for use as an anti-viral drug to treat the flu. Importantly, after reviewing the data from this initial clinical trial, the drug was approved by the FDA to shorten the duration of illness due to influenza, but not for preventing complications like secondary bacterial infections that could occur due to the illness. Tamiflu also earned a spot on WHO’s List of Essential Medicines.  

Things got complicated when the Cochrane Collaboration became involved. The Cochrane Collaboration is a non-profit organization that performs systematic, transparent reviews of all clinical trials to help physicians decide for instance how well a drug works for a certain indication and whether Oseltamivir is effective for a certain medical condition, and common side effects of Oseltamivir. A Cochrane Systematic Review on Tamiflu was conducted by this organization in 2009. These reviews are publicly available for review by clinicians, and a comment by a Japanese doctor led the scientific community to discover that the clinical trial data on Tamiflu was limited, suggesting that the information was not reliable enough to conclude whether there was any benefit to taking Tamiflu for an Influenza infection. 

Subsequent to this, Roche was contacted to clarify results of the clinical trial and over the following few years it was discovered that much of the clinical trial data was missing or inaccurately represented. Further in 2014, another Cochrane Review and a simultaneous report published by the BMJ pushed previously unavailable clinical trial data to become public, allowing health officials and physicians to draw a better conclusion on how well Tamiflu works. It was judged that the drug can reduce the duration of the symptoms experienced due to the illness by one to two days, but does not prevent the occurrence of secondary complications like hospitalization due to pneumonia. 

After this new information became publicly available, in 2017 the World Health Organization removed oseltamivir from its List of Essential Medicines. But this has not stopped Tamiflu/oseltamivir from being prescribed as an FDA-approved anti-viral therapy to combat the flu caused by Influenza type A and type B viruses. Currently, the CDC, EMA and other organizations still recommend the use of this drug to treat high-risk individuals that are afflicted with the flu. 

Current clinical trials for COVID-19

Currently, several anti-viral drugs that are currently on the market are being investigated as potential therapeutic agents against COVID-19 caused by the SARS-CoV-2 virus.

Oseltamivir is one such anti-viral drug included in this list that is being tested in combination with other existing anti-viral drugs. Clinical trials around the world have begun to test their safety and efficacy in treating COVID-19 in humans.

One trial using oseltamivir is ongoing in Thailand. The SARS-CoV-2 virus is different from the Influenza virus, so without obtaining results of the clinical trial data, it is uncertain whether this drug will be helpful for treating COVID-19.

How to get Oseltamivir at a discounted price

If your doctor prescribes Tamiflu/oseltamivir for treating the flu, they have judged that the benefits of taking the drug will most likely outweigh its risks. It is important to take oseltamivir exactly as prescribed by your doctor. You will need a prescription to fill this drug.

The cost of Tamiflu can vary according to the pharmacy you get it filled at and according to your health insurance plan. Drug discount cards can help you find the drug at a more affordable price. The free discount card offered by Pharmacists.org can get you on average of 51% savings on the list price of the drug. You can sign up for the card online and take the discount card with you when you get your prescription filled.

The price of Tamiflu with the discount card can be even cheaper than a co-pay amount with certain health insurance plans. Ask your pharmacist to compare these prices for you and apply the discount card if the savings are more with the card.  

Preventative measures like getting a flu shot are still recommended during flu season. If you do get the flu, oseltamivir may be prescribed to you depending on the severity of your illness and your personal medical history. Even though oseltamivir has an interesting and somewhat controversial history of how accepted it is to treat Influenza infections, it is still currently one of the major anti-viral drugs used to treat the flu around the world. Understanding how to take this drug is important to get the benefits of taking it. 

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