I think that was the same antibiotic my DR. prescribed to me after taking out my wisdom tooth out. Apparently, it didn't seem to have any interaction with the estradiol I was taking orally, confirmed by his office and pharmacist BUT I did feel out of sorts during that time, very tired...maybe due to the antibiotics effect, nothing more. I don't recall seeing breast shrinkage, in fact, breast growth continued and all seemed well. I also took probiotics and regularly ate yogurt (kefir is even better) to maintain good bacteria in my gut as antibiotics can adversely affect gut flora. I didn't get nausea or have diarrhea, thankfully. Just really very tired.