Side Effects of Tamiflu
According to the company who developed the drug, Gilead Science, a total of 1171 patients who participated in adult phase III controlled clinical trials for the treatment of influenza were treated with Tamiflu. The most frequently reported adverse events in these studies were nausea and vomiting.
The summary of clinical testing includes 945 healthy young adults and 495 “at risk” patients such as elderly patients and patients with chronic cardiac or respiratory disease. These people were tested to see what effects the drug would have on people with other illnesses. Those events reported numerically more frequently in patients taking Tamiflu compared with placebo were nausea, vomiting, bronchitis, insomnia, and vertigo.
The last of these, bronchitis, insomnia and vertigo being reported with less frequency. There were some common adverse drug reactions associated with Tamiflu therapy including nausea, vomiting, diarrhea, abdominal pain, and headache. In some instances there are more serious adverse drug reactions but they are rare. These include hepatitis and elevated liver enzymes, rash, allergic reactions including anaphylaxis, and Stevens-Johnson syndrome.
Various other adverse drug reactions have been reported which include toxic epidermal necrolysis, cardiac arrhythmia, seizure, confusion, aggravation of diabetes, and haemorrhagic colitis.
In May 2004, the safety division of Japan’s health ministry ordered changes to the literature accompanying Tamiflu to add neurological and psychological disorders as possible adverse effects, including: impaired consciousness, abnormal behavior, and hallucinations. Various cases of psychological disorders were associated with Tamiflu therapy between 2000-2004, including several deaths.
Resistance is of concern in the scenario of an influenza pandemic, since resistance is more likely to develop due to the potentially longer duration of infection by novel viruses. The genetic sequence for the neuraminidase enzyme is highly conserved across virus strains. This means that there are relatively few variations, and there is also evidence that variations that do occur tend to be less “fit.” Thus, mutations that convey resistance to Tamiflu may also tend to cripple the virus by giving it an otherwise less-functional enzyme. The lack of variation in neuraminidase gives two advantages to oseltamivir and zanamivir, the drugs that target that enzyme. First, these drugs work on a broader spectrum of influenza strains. Second, the development of a robust, resistant virus strain appears to be less likely.
As with any prescribed drug, talk to your doctor before taking Tamiflu and make sure to tell your doctor about an other drugs you may be taking.
