Dear Thanks for contacting HCM I would like you to know that Clindamycin use may sometime cause severe diarrhea which is due to alteration in flora and fauna of digestive system, this may allow Clostridium difficile (bad bacteria) to have an upper hand in the digestive tract leafing to Clostridium diffocile associated diarrhea (CDAD). Generally it is self limiting and it responds to discontinuation of antibiotic, supportive Care, and fluid and electrolyte replacement. However, if diarrhea persists, effective antimicrobial agent against Clostridium difficile is often necessary but for it diagnosis of Clostridium difficile infection is necessary ( metronidazole is preferred treatment). Hope this has helped you Regards