The FDA recently granted fast-track status for the drug MuDelta which was created by Furiex Pharmaceuticals. MuDelta is a combo delta opioid receptor agonist(stimulates) and a mu receptor antagonist(blocks stimulation). The drug has similarities to another opioid receptor drug Naltrexone, however Naltrexone is purely a opioid receptor antagonist for the mu, kappa & to a small extent delta receptors. It does not have agonist properties and thus doesn’t stimulate any of the receptors.
Opioid receptors play a big part in how our body works. The delta receptor can play a part in depression, kappa can have sedating effects or cause dysphoria, while the mu(and it’s subtypes) control things like euphoria and gastrointestinal motility. Since MuDelta focuses on stimulating the delta receptor while reducing stimulation on the mu receptor, one would deduce that they are probably trying to simulate an antidepressant effect, while reducing signals to the the gastrointestinal tract. This seems like it could work as many have had success with treating Irritable Bowel Syndrome via antidepressants and antispasmodics.
While this idea is not entirely new(see Naltrexone), MuDelta may prove to be a more targeted drug for Irritable Bowel Syndrome.