Sensory and affective pain descriptors respond differentially to pharmacological interventions in neuropathic...

Pain management is limited by inability to match a patient's condition-and pain mechanisms-to optimal treatment(s). Much is known about pain treatment from animal investigations, but antinociceptive mechanisms cannot be readily explored in clinical studies. Evidence suggests that self-report verbal pain descriptors characterize important pain dimensions and may reflect diverse underlying mechanisms.

This exploratory analysis of data from a trial of a gabapentin-morphine combination evaluated effects of treatment on short-form McGill Pain Questionnaire sensory and affective descriptor profiles and prediction of treatment response by these descriptors.

Severity of "throbbing," "shooting," and "aching" improved preferentially with morphine over gabapentin, whereas "tiring-exhausting" and "sickening" improved preferentially with gabapentin over morphine. Improvement in descriptor severity with gabapentin-morphine combination was superior to active placebo for 12 of 15 short-form McGill Pain Questionnaire descriptors, whereas morphine and gabapentin were superior to active placebo for only 7 and 6 descriptors, respectively. Baseline moderate-severe "throbbing" and "hot-burning" predicted poor outcomes with gabapentin, whereas moderate-severe "aching" and "punishing-cruel" predicted favorable outcomes with gabapentin. Baseline "throbbing" severity also predicted poor outcomes with morphine. Baseline allodynia predicted superior reduction of "stabbing" with morphine but not with gabapentin alone.

These results point to the hypothesis that sensory and affective pain descriptor profiles exhibit a treatment-specific response. Larger, more definitive, investigations to evaluate treatment-specific effects on multiple sensory and affective pain descriptors, and prediction of treatment response by these descriptors, will advance efforts toward developing and implementing more effective individualized pain therapies.