Sensory and Affective Pain Descriptors Respond Differentially to Pharmacological Interventions in Neuropathic Conditions

OBJECTIVES: 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. METHODS: 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. RESULTS: 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. DISCUSSION: 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.