I have been taking 1500 mg (3 capsules of 500mg each) of amoxicillin for 28 days to treat Lyme's Disease. For the past 4 days, my stools have turned/been black. Would amoxicillin capsules cause this? Should I be concerned? Will my stools go back to normal now that treatment has ended? I haven't had any other noticeable problems. I am worried about the black stools. Also, can Penicillin injection be used, instead, to treat Lyme's? (I am not allergic to Penicillin, and it worked well to treat pneumonia when I had it years ago.) What do I need to do about the black stools?