M320 is an extremely potent and long acting opioid. It produces long lasting narcosis in different animals, including mice, rats, cats, guinea pigs, dogs and monkeys. M320 is a ü and ú-opioid receptor agonist. Similarly to TL 2636, M320 tends to produce pronounced nausea and vomiting due to its potent agonist activity at both the ü and ú-opioid receptors at the same time.