Narcotic analgesia: fentanyl reduces the intensity but not the unpleasantness of painful tooth pulp sensations.

Forty subjects rated the magnitude of painful electrical stimulation of tooth pulp before and after the intravenous administration of either fentanyl, a short-acting narcotic, or a saline placebo. The responses were choices of verbal descriptors from randomized lists of either sensory intensity (that is, weak, mild, intense) or unpleasantness (annoying, unpleasant, distressing) descriptors. The fentanyl significantly reduced the sensory intensity without reducing the unpleasantness of the tooth pulp stimuli, indicating that the mechanisms of narcotic analgesia may include a significant attenuation in pain sensation in addition to effects on pain reaction. These results stress the importance of using multiple measures of pain.