"Taking Medicine to Recover from Flu Leads to Bloody Stool... Suspected Side Effect Cases Surge"

Experts: "No Need to Hesitate About Taking the Medication"

As suspected cases of influenza, an acute respiratory disease caused by a virus, are explosively increasing, reports of side effects from Tamiflu, the most commonly used treatment, are spreading mainly online.

On the 13th, as influenza, COVID-19, and respiratory syncytial virus (RSV) are simultaneously spreading, a children's specialty hospital in Seongbuk-gu, Seoul, is crowded with children and their guardians seeking respiratory health care. Photo by Kang Jin-hyung

Tamiflu is an oral medication taken twice a day for five days. It does not attack the virus directly but inhibits the replication of the virus that has entered the body. Therefore, it must be taken within 48 hours after symptoms appear to be effective. Since it does not directly attack the virus, flu symptoms tend to persist for a while even after taking the medication.

When taken within 48 hours, it is very effective in relieving symptoms, but side effects are sometimes reported. Common side effects include vomiting, insomnia, headaches, and hemorrhagic colitis. Cases shared online range from mild symptoms such as "frequent stomach burning" and "dizziness" to more severe experiences like "abdominal pain followed by diarrhea and seeing blood despite no hemorrhoids."

In infants and young children, neuropsychiatric adverse reactions such as hallucinations and delirium have also been reported. In South Korea, the prescription of Tamiflu became controversial after a middle school student had a fall accident in 2018 following Tamiflu use. A pediatric specialist explained, "The hallucination controversy related to Tamiflu may be due to abnormal behavior caused by high fever rather than the drug itself. Because such hallucinations mainly occur in children and adolescents, there is a hypothesis that antiviral drugs might affect the nervous system of children and adolescents, whose nervous systems are not yet fully developed."

Other symptoms besides hallucinations cannot be clearly distinguished as caused by Tamiflu or the virus. Patients infected with the influenza virus can experience nausea, vomiting, headaches, and hallucinations even without taking medication.

Experts advise that these side effects are extremely rare, so there is no need to hesitate to take the medication out of fear of side effects. It is also important not to stop taking the medication arbitrarily due to concerns about side effects, as resistant viruses may develop and symptoms can reoccur. Especially for high-risk groups with weakened immunity, the illness can progress to a serious condition. Furthermore, given the recent severe spread of infectious diseases, it is recommended to get vaccinated to prevent reinfection or complications even if one has already contracted influenza.