Im taking doxycycline 100mgx2 a day, and topical clindamycin for acne. its been about a 1 1/2 week since im on it, and little more constipated and stool is more blackish. cause of concern?can antibiotics cause this? on and off. pepto b sometimes?

Doxycycline is a very broad spectrum antibiotic. This can change the bacterial flora in your colon and also change the color of the stool along with the function of the colon. It is a good idea to take a probiotic daily to help rebalance the bacterial flora in your bowel.

Agree with Dr Ellis. Additionally, I don’t recommend PeptoBismol. Please contact your doctor if your stools are pure black or if you see blood.