After receiving reports of patients experiencing delirium, psychosis and hallucinations, US FDA staff recommend that flu drugs, Tamiflu and Relenza should carry warnings about possible side-effects. Tamiflu is made by Roche Holdings, Relenza is made by GSK (GlaxoSmithKline).
Tamiflu (oseltamivir) is a pill, while Relenza (zanamivir) is inhaled.
Reports from Japan indicate that children, particularly, may have a higher risk of experiencing these psychiatric side effects after receiving the flu drugs. Tamiflu and Relenza are the most common medications used for the treatment of flu. Apart from the said side effects, there have also been reports of deaths.
The safety of these treatments come under review next week by a panel of experts. The FDA staff announced their recommendations today – they say the warning should be directed at patients of all ages, not just children. Whether the side effects and deaths were caused just by the drug(s), the flu virus, or the two together is not clear, they explain. They said it would be prudent to add information to the labeling, and added that the products will continue to be monitored. They did not go as far as suggesting that the use of the drugs should be limited.
Over the last few years governments throughout the world have been building up their stocks of Tamiflu as a precaution to a possible future mutation of the H5N1 bird flu virus, which could cause a serious flu pandemic. As recent concerns regarding Tamiflu have surfaced, its sales have lost some steam. Tamiflu sales are 62% lower this year when compared to 2006, while Relenza sales have dropped 7%.
FDA employees looked at 596 cases – most of them in Japan – of patients experiencing psychiatric side-effects which may be linked to Tamiflu use. Three Japanese adults committed suicide while on Tamiflu while five children died. Since 1999, when Relenza was approved, there have been 115 reports of psychiatric events, of which 74 were children.
The Japanese Ministry of Health warned against Tamiflu use for patients aged 10-19 in March 2007. The ministry then broadened its investigation of Tamiflu to include Relenza and amantadine, after reports came in of abnormal behavior among children.
Tamiflu is more commonly used in Japan than in the USA. Worldwide, approximately 48 million people have taken Tamiflu since 1999, of which 21 million are children.
According to Roche, there is no definite proof of a causal relationship between Tamiflu and abnormal behavior. The company says it has researched this topic at length – clinical and non-clinical studies are currently being carried out.
Written by – Christian Nordqvist