Difenoxin

Difenoxin (Motofen) is a 4-phenylpiperidine derivative that is related to the opioid analgesic drug pethidine (meperidine).

Difenoxin is an active metabolite of the anti-diarrhea drug diphenoxylate. It is not used by itself and is a Schedule I drug in the USA, however in some countries a combination product containing difenoxin and atropine is used to treat diarrhea, in a similar way to how diphenoxylate itself is used.

Difenoxin also has some sedative and analgesic effects as with other opioids, but diphenoxylate itself is a relatively weak analgesic, and difenoxin has similarly limited analgesic effects, although it is a potent anti-diarrhoreal drug. Research suggests that additional non-opioid mechanisms may also be involved in the action of difenoxin, explaining its strong anti-diarrhoreal effects despite only limited opioid action.