@Romla, they do have the same chemical composition but some ladies on this site have said that they tried a different brand and did notice a change in side effects. Maybe it doesn't effect everyone the same but for me it's not worth the risk. I've also been taking a vitamin cocktail each morning along with Arimidex for the past 14 months and again, something is working for me so I'll just keep on going. And cross my fingers that the drug companies eventually do the right thing and reduce the price of drugs which are helping keep us cancer free.