 It is also the endogenous ligand of the opioid growth factor receptor (OGFR; formerly known as the ζ-opioid receptor), which plays a role in the regulation of tissue growth and regeneration; hence why met-enkephalin is sometimes called OGF instead.Met-enkephalin has low bioavailability, is rapidly metabolized, and has a very short half-life (minutes).These properties are considered undesirable in pharmaceuticals as large doses would need to be administered multiple times an hour to maintain a therapeutically relevant effect, making it unlikely that met-enkephalin will ever be used as a medicine.