Have been on this medicine for seven years as my doctor says that the trial period has only been up to five years and I can continue to take it as extra insurance. But I had one side effect, such as hair thinning, and this problem is starting to bother me. You should to know more information about side effects every drugs, which you want to use. Information about other medicines read here. 3 of my relatives who had started taking this drug the same time I did and who had other oncologists, were taken off Arimidex after five years. And they stopped usage of this drug, because also had hair thinning.