Bakdom Im not sure of the timeframe. Im 51 and pre menopausal. My onc told me after 2 years he would be testing me to see if Im officially "neutered"...(my descriptive word). Ive had my second injection and once again it didnt hurt. My onc gave me a Emla patch to use beforehand and my GP gave me the injection. So for the next 4 months its Tamoxifen and Zoladex for me...then switching to an AI. I must admit, I am trying to remain positive about switching to an AI, but Im googling too much...I MUST, I MUST STOP GOOGLING and finding one million horrid side effects!!!