Sorry you had so much problems with that drug. I know it is like Cipro but I have taken Cipro so much with protate infections, urinary tract infectiions(2), and many diverticular infections and intestinal problems.
I have never had black stools or any other side effects that I know of.
I have never taken it longer than 7 days and I alway take probiotic supplements several times daily and eat yogurt while taking Cipro. I also take a psyllum fiber supplement daily --- every day.
I also took the minerals that mess with Cipro's absorption--- like zinc, magnesium and calcium about 3 hours after Cipro.
The antibiotics that I have had the most trouble with it Amoxicillin causes candida infections that are difficult for me to deal with and Flagyl -- I can take-- too much cramping.
I certainly wish you well---Harry