“How long should I take medications for diarrhea?”

Depends n how long it lasts. For acute self-limited diarrhea then meds may be needed for a week or less.
For chronic diarrhea, a more specific diagnosis should be sought.

Not very long if at all It is possible that the diarrhea is your body's attempt to rid itself of a toxin and by preventing this you are potentially putting yourself at great risk ( eg if you have C. difficile) If the diarrhea persists, see a GI to figure out why Better to eradicate the cause than the symptoms.