Nalbuphine, 10 mg IM, produces analgesia with an onset of effect and duration similar to morphine. Depression of ventilation is similar to morphine until 30 mg IM of nalbuphine is exceeded, after which no further depression of ventilation occurs (ceiling effect).
The plateau (ceiling) effect mechanism is due to nalbuphine’s partial agonist/antagonist properties and holds true for all major effects: opiate, euphoria, and respiratory depression. After a certain point, taking higher dosages won’t result in much intoxication, but it also won’t cause much risk of respiratory depression and possible overdose death.
For this reason nalbuphine is considered to have a reduced addiction liability and is commonly used to treat opiate addiction.