RB-120 is an orally active analog of the drug RB-101. It acts as an enkephalinase inhibitor, which is used in scientific research. Via intravenous administration, it is approximately three times as potent as RB-101 or twice as potent as the isolated (S,S) isomer of RB101. However, via i.p. administration it is approximately twice as potent as racemic RB-101 and about as potent as the isolated (S,S) isomer of RB101. During i.v. administration RB120 is approximately twice as weak as morphine in terms of analgesia; however, it is 16x weaker during i.p. and p.o. administration.