Use of gabapentin for attenuation of symptoms following rapid opiate detoxification (ROD)--correlation with neurophysiological parameters--.

Rapid opiate detoxification (ROD) is a technique whereby the opiate-dependent patient is withdrawn acutely, under anesthesia, from the opioid. Following detoxification, patients experience severe back pain and restlessness often accompanied by a restless-leg-syndrome. We evaluated gabapentin given immediately following detoxification to attenuate these symptoms. In addition, we evaluated the use of the somatosensory-evoked potential (SEP) as a parameter to quantitate pain responses. Patients (n=21; mean age 32.5 +/- 7 SD; 12 males, 9 females) underwent ROD with naltrexone (2 x 50 mg) during propofol anesthesia and artificial ventilation (IPPV). Sympathetic overshoot was attenuated by clonidine, and increased bowl movement was managed by continuous i.v. somatostatin. Back pain, restlessness, and restless-leg-syndrome were treated with gabapentin (1200 mg) in the ICU. Efficacy was assessed by the patient's subjective ratings of restlessness (0-4). In addition, measurements of amplitude (microV), latency (ms) of late N100-peak of the somatosensory evoked potential (SEP), and tolerance to an increased electrical nociceptive stimulus (mA) to the forearm were performed. Data were compared to pre-treatment control and to the period shortly after detoxification. From a mean of 8.4 +/- 2.5 microV, N100-peak increased to a mean of 12.3 microV +/- 3.3 (p < 0.005) following opioid detoxification. Gabapentin reduced amplitude height to a mean of 3.5 +/- 1.5 microV. Also, tolerance to nociceptive stimulus, which had dropped to 4.4 mA, increased to 12.5 mA (p < 0.01), while intensity for restlessness and thrashing of limbs dropped from 3.2 to 1.2 (p < 0.05). The sudden displacement of the opiate from its receptor site induced by naltrexone, resulted in a post inhibitory SEP overshoot with an increase in nociceptive afferent volleys, and a lowering in pain threshold. This was associated with back pain, limb thrashing and a restless-leg-syndrome, all of which could be attenuated by gabapentin. The amplitude of late N100-peak parameter appears to be a potential candidate to quantify the increase of nociception in such patients.