Crystalization of oseltamivir phosphate, the active ingredient in Tamiflu

Photo courtesy Roche

Tamiflu Basics

Tamiflu (oseltamivir phosphate) is an antiviral drug marketed by the Swiss pharmaceutical company Roche. It belongs to a group of drugs called neuraminidase inhibitors and can shorten the duration and lessen the severity of the type A and B strains of the flu, as well as bird flu.

Each 75-milligram capsule contains the active chemical oseltamivir, as well as several inactive ingredients. Scientists synthesize oseltamivir from shikimic acid, a naturally occurring substance found in plants like Chinese star anise, ginkgo, spruce, pine and fir trees.

Roche primarily obtains shikimic acid from the Chinese star anise, a spice found in the star-shaped fruit of the Illicium verum, a small evergreen tree. Roche uses a specific type of anise that grows in four mountain provinces (Guanxi, Sichuan, Yunnan and Guizhou) of southwest China. Because these regions are high altitude and have a hot, humid, climate, they produce a higher purity and greater yield of star anise than other regions.

Tamiflu capsules with star anise fruit and pods

Photo courtesy Roche

The manufacture of Tamiflu involves a complex, 10-step process that takes approximately 6-8 months to complete. First, a Roche supplier extracts shikimic acid from the pods (the part that wraps around the seeds) of the star anise. The remaining steps involve a series of complex chemical reactions. Thirty kilograms (66 pounds) of star anise produces only 1 kilogram (just over 2 pounds) of shikimic acid.

Although most shikimic acid comes from star anise, Roche and its partners are increasingly using fermentation to produce it. Roche uses a special strain of the E. Coli bacteria in its fermentation process. When these bacteria are overfed glucose, or sugar, they produce shikimic acid. This process could produce greater yields of shikimic acid, and scientists are working to improve the fermentation process so they can use it more readily.

Tamiflu targets a protein called neuraminidase that lives on the flu virus cells. This protein helps the flu virus break through the cell walls so it can move on to other cells and replicate itself. Tamiflu inhibits the neuraminidase protein, so that the virus can't leave the cell to infect other cells. Eventually, the virus dies.

Photo courtesy Roche

Tamiflu can't stop the flu entirely. However, studies have shown that if you take it within 48 hours of showing symptoms, it can shorten the duration of the flu (strains A and B). Patients with the flu who took it felt better 30 percent (or 1.3 days) faster than people who didn't take it [ref]. The drug also can help protect you from getting the flu if you're exposed to someone who has it. But Tamiflu can't prevent the spread of the disease, and it won't stop illnesses (like the common cold) that resemble the flu.

Tamiflu isn't cheap, either. A 10-dose course can cost $60 to $80 in the United States. Currently there is no generic version of the drug available in the U.S.

Between 2004 and 2005, 12 children in Japan reportedly died after taking Tamiflu. However, the children also had neurological problems that could have been associated with the flu itself. In November 2005, the Pediatric Advisory Committee of the FDA ruled that the drug was safe for children [ref].

We'll find out how Tamiflu stands up to bird flu in the next section.