Meperidine is a mu agonist that appears to have effects similar to local anesthetics by blocking sodium channels and the activity of neurons in the dorsal horn of the spinal cord.  Meperidine also features some weak alpha2 adrenergic agonist activity and anticholinergic effects.11, 12

Because of these effects, meperidine tends to produce reliable sedation while maintaining, even increasing, heart rate (unlike other opioids). Meperidine has a relatively short duration of action (about 1 hour) and can produce histamine release when bolused intravenously.13 For this reason, meperidine is typically used intramuscularly as a premedicant.