U-48800 is an opioid analgesic that acts as a selective agonist. U-48800 is an analog of U-47700, just added one methylene on the benzene ring, at the same time, 2,4-dichlorophenyl replaced the 3,4-dichlorophenyl. U-48800 is selective for the µ-opioid receptor, having around 7.5 x the potency of morph in animal models.

Research results shows that U-48800 has the same potency level as originally U-47700.