Tamiflu is marketed by Gilead as capsules containing oseltamivir phosphate 98.5 mg equivalent to oseltamivir 75 mg, also as a powder for oral suspension containing oseltamivir phosphate which is equivalent to oseltamivir 12 mg per ml.

The medicine is used to treat flu which is an infection caused by influenza virus. Tamiflu belongs to a group of medicines which are known as neuraminidase inhibitors. These medications attack the influenza virus and prevent it from spreading inside a person’s body. Tamiflu has been promoted to be effective against the Bird Flu virus during the recent outbreaks.

By targeting the virus at its source, Tamiflu treats flu, rather than simply masking symptoms. A number of the old flu remedies used to treat the symptoms but did nothing to actually combat the flu virus. The Tamiflu capsule, which is coloured grey and light yellow, contains 75 mg of the active drug and is taken by mouth.

Being generally well tolerated Tamiflu may cause mild-to-moderate nausea or vomiting in one out of ten people but, by taking Tamiflu with food can reduce the potential for these side effects. You are less likely to have problems than you would by taking the medication on an empty stomach. Some less reported side effects may include bronchitis, sleeplessness and vertigo.

Some commonly reported adverse drug reactions associated with Tamiflu therapy includes nausea, vomiting, diarrhea, abdominal pain, and headache. There have been rare adverse drug reactions which include hepatitis and elevated liver enzymes, rash, allergic reactions including anaphylaxis, and Stevens-Johnson syndrome.

Very rare, but reported, are toxic epidermal necrolysis, cardiac arrhythmia, seizure, confusion, aggravation of diabetes, and haemorrhagic colitis, and there have been some neurological effects reported as well.

The United States Food and Drug Administration in 2005 issued a report regarding the pediatric safety of oseltamivir. This stated that there was insufficient evidence to claim a causal link between oseltamivir use and the deaths of 12 Japanese children. However, the FDA recommended that a warning was added to the Product Information regarding rashes associated with oseltamivir therapy.

Tamiflu is designed to prevent all common strains of the influenza virus from replicating; this replication process is the contributing factor to the worsening of symptoms in a person infected with the influenza virus. In common with many other prescription drugs, Tamiflu needs to be monitored by your doctor.

Neuraminidase inhibitors are designed to inhibit, or "plug" the active site of an enzyme, called neuraminidase and this neuraminidase can be found protruding from the surface of the two main types of influenza virus, type A and type B. This enables newly formed viral particles to travel from one cell to another in the body. Tamiflu, by inactivating neuraminidase, this viral replication is stopped, stopping the spread of the influenza virus.