Did you find out if it was okay to start taking this? On the drug info page it says to let your doctor know if you are taking any other antibiotics while taking keflex. But technically if you already stopped taking the amoxicililn then you might be safe to take keflex. Sometimes you might be prescribed a different antibiotic so that the bacteria don't build a tolerance in your body to the original one you were on. But it is definitely best to triple check with your doctor about this. Is it for the same infection or for a new infection as when you were first on the amoxicillin ?