antibiotic - associated diarrhea , such as that caused by clostridium difficile , represents a serious medical complication that can result from administering a broad - spectrum antibiotic to a subject . such diarrhea leads to significant potassium loss from the subject . the present invention discloses a polymeric therapeutic agent that treats antibiotic - associated diarrhea and is physiologically potassium neutral . this polymer contains polystyrene sodium sulfonate and polystyrene potassium sulfonate repeat units .