Introduction

Oseltamivir phosphate is a white or almost white crystalline powder with the chemical name ethyl(3R,4R,5S)-4-acetamido-5-amino-3-(1-ethylpropoxy)-cyclohex-1-ene-1-carboxylate phosphate. It is an influenza viral neuraminidase inhibitor used in the prevention and treatment of influenza.

Application in the treatment of influenza

• Introduction of influenza

Influenza, also called flu or grippe, is an acute viral infection of the upper or lower respiratory tract. It is characterized by a runny nose, sore throat, cough, fatigue, fever, chills, and a generalized feeling of weakness and pain in the muscles, together with varying degrees of pain in the head and abdomen. These symptoms usually begin from 1-4 days (most commonly 1-2 days) after exposure to the virus and last for about 2-8 days[1]. There are four types of influenza virus: A, B, C, and D. Of these, the influenza A virus is responsible for most cases of severe illness, seasonal epidemics and occasional pandemics.

It is estimated that there are 3-5 million severe influenza cases and about 650000 influenza-related deaths globally each year. Deaths most commonly occur in high-risk groups, including young children, the elderly, and people with chronic health conditions.

• Mechanism of action

Oseltamivir phosphate is hydrolyzed in the liver to its active form and which is a potent and selective inhibitor of influenza virus neuraminidase. This enzyme is important for the entry of the virus into uninfected cells, the release of newly formed virus from infected cells, and the further spread of the infectious virus in the body. Thus, oseltamivir phosphate treats influenza by reducing viral infectivity. Clinical practice has shown that it is only effective against neuraminidase of influenza A virus (including pandemic H1N1) and influenza B virus.

• Side effects

Common side effects of oseltamivir phosphate mainly include: nausea, vomiting, diarrhea and headache disorder.

Rare side effects of oseltamivir phosphate mainly include: rash, itching/swelling, severe dizziness and trouble breathing.

Oseltamivir phosphate may rarely cause serious mental/mood changes. However, side effects such as confusion, agitation and self-injury may occur in children.

Reference

1. Dharmapalan, D. Influenza. The Indian Journal of Pediatrics. 2010, 87: 823-832.