Combination of low frequency electroacupuncture plus subdissociative doses of ketamine in post-herpetic neuralgia patients. A pilot study

Context: Pain processing implicates multiple concurrent mechanisms of nociceptive transmission and modulation. Electroacupuncture (EA) analgesia involves mainly the activation of the endogenous anti-nociceptive systems that modulate pain transmission in addition to the regulation of glial activity and inhibition of pro-inflammatory cytokines in the spinal cord. Aims: To examine the potential anti-hyperalgesic effects the EA and the combination EA-ketamine in patients with post-herpetic neuralgia (PHN). Methods: Sixty-eight patients with PHN irritable nociceptor type were randomly allocated to 3 groups: group I (n=26), that received treatment with EA (10 Hz, 2-3 mA, 0.5 ms, 20 min/15 sessions) alone, group II (n=21) with a combination EA-ketamine (0.25-0.5 mg/kg, i.m.) or group III (n=21) with sham EA-ketamine for 15 days. The average daily pain score (ADPS) using the Likert scale, area and rate of dynamic allodynia, the rate of thermal allodynia, and frequency of intermittent lancinating pain were evaluated during five visits – before treatment and at 15, 30, 60, 90 days. Results: ADPS and sensory abnormalities decreased significantly concerning baseline data at 90 days in the three groups, but patients treated with the combination EA-ketamine significantly improved compared with the other groups. Conclusions: These results suggest that the combination EA-ketamine shows an early and long-term anti-hyperalgesic effect in PHN patients. However, a controlled clinical trial is necessary to confirm this hypothesis.