Antiviral preparations / Drugs used in Flu treatment
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Drugs used in Flu treatment

Influenza is an acute infectious respiratory disease caused by influenza virus. There are 3 flu viruses known to the science:

  • type A: usually causes moderate to severe disease. It affects both people and some animals (horses, pigs, ferrets, birds). In particular, influenza A viruses are responsible for the emergence of pandemics and severe epidemics.
  • type B: usually causes local eruptions and epidemics, sometimes covering one or more countries. Influenza viruses B circulate only in the human population (most frequently causing the disease in children).
  • type C that is rather poorly studied. This virus infects only people. Its symptoms are usually very light or do not appear at all. It does not cause epidemics and does not lead to serious consequences. It is the cause of sporadic diseases, most often in children. Diseases caused by influenza virus C often coincide with the epidemic of influenza type A. The clinical picture is the same as in the light and moderately severe forms of influenza A.

Influenza virus is easily transmitted. The most common mode of transmission is airborne.

Flu symptoms
Influenza is an acute highly contagious disease, characterized by toxicosis, moderate catarrhal symptoms with the most intense lesion of the trachea and major bronchi.

Usually, influenza begins acutely. The incubation period usually lasts 1-2 days but can last up to 5 days. Then starts a period of acute clinical manifestations. The severity of the disease depends on many factors: general health, age, etc. Depending on this, the patient may develop one of the 4 forms of influenza: mild, moderate, heavy and hypertoxic. Symptoms and their strength depends on the severity of the disease.

In the case of light forms of influenza, the body temperature may remain normal or may increase no higher than 38 ° C, the symptoms of infectious toxicosis are lightly expressed or absent.

In the case of moderate form of influenza the temperature rises up to 38,5-39,5 ° C and the classic symptoms of the disease are present as follows:

  • Intoxication
    • heavy sweating
    • weakness
    • photophobia
    • articular and muscular pain
    • headache
  • Catarrhal symptoms
    • hyperaemia of soft palate and posterior pharyngeal wall
    • hyperaemia of conjunctiva
  • Respiratory symptoms
    • failure of the larynx and trachea
    • dry (in some cases - wet) painful cough
    • violation of phonation
    • chest pain
    • rhinitis (runny nose)
    • hyperemia, cyanosis, dry mucous membrane of the nasal cavity and pharynx
  • Pulmonary heart disease
  • Abdominal syndrome: abdominal pain, diarrhea

In the severe form of influenza, the body temperature rises up to 40-40,5 ° C. In addition to the symptoms associated with moderate forms of flu, there are signs of encephalopathy (psychotic states, seizures, hallucinations), vascular disorders (nasal bleeding, punctate hemorrhage in the soft palate), and vomiting.

With the first symptoms of the flu, it is recommended to start the therapy as soon as possible. There are two groups of anti-influenza drugs with proven clinical efficacy: M2-channel blockers - amantadine, rimantadine, and inhibitors of viral neuraminidase - zanamivir, oseltamivir. Amantadine and remantadine relieve the clinical symptoms of influenza and reduce the duration of illness by an average of 1,5-3 days. However, it should be noted that they have a specific activity only against influenza virus A, and powerless against the influenza virus B.

The mechanisms of antiviral activity of amantadine and rimantadine are not clear. It is known that both drugs violate the replication of influenza virus A. These preparations directly interact with viral protein M2 that forms ion channels in the infected cells providing the initial stages of viral replication. Ion channels are involved in the process of inflammation in the cells of the upper respiratory tract. It is the inflammation that is a key factor in the spread of viral infection. Therefore, blocking the function of the ion channel leads to the fact that the virus loses the opportunity to multiply and destroy tissue cells of the upper respiratory tract.

Treatment with these drugs is effective only if started during the first 48 hours after onset of the flu. Rimantadine in the final stages of the reproductive cycle of influenza A virus blocks the transmission of the virus to healthy cells. Consequently, the disease does not develop further and does not lead to possible complications. The remantadin and amantadine therapy should be carried out during the whole period of the disease until symptoms disappear.

Zanamivir and oseltamivir being the inhibitors of viral neuraminidase disrupt the ability of viruses to penetrate healthy cells, inhibit the release of virions from infected cells and decreases their resistance to the inactivating action of mucous secretion of the respiratory tract, resulting in suppression of the further spread of the virus in the body. In addition, zanamivir and oseltamivir reduce production of certain cytokines, preventing the development of local inflammation and weakening the systemic appearance of viral infection (fever, etc.). The inhibitors of viral neuraminidase are effective against both viruses A and B.