Complex sentence: For adults, the dosage is that which causes a powerful daily bowel movement which cannot be ignored or resisted for any length of time without a feeling of panic developing followed by an explosive diarrhea.
Split into simpler sentences: For adults, the dosage is that which causes a powerful daily bowel movement. If there is an attempt to ignore or resist having a bowel movement for any length of time, a feeling of panic develops followed by an explosive diarrhea.