Clinical neuropharmacology
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Clin Neuropharmacol · Aug 1995
Randomized Controlled Trial Clinical TrialIntravenous infusion of the NMDA antagonist, ketamine, in chronic posttraumatic pain with allodynia: a double-blind comparison to alfentanil and placebo.
NMDA antagonists and opioids relieve experimentally produced hyperalgesia in animals and humans, presumably by attenuating a heightened central nervous system response to afferent input. A few small studies in patients have suggested that intravenous boluses or rapid infusions of the N-methyl-D-aspartate (NMDA) antagonist ketamine relieve some neuropathic pains but also produce disturbances of cognition and mood. In a randomized, double-blind, crossover trial, we treated eight patients with chronic posttraumatic pain and widespread mechanical allodynia with 2-h intravenous infusions of the NMDA antagonist ketamine (mean dose, 58 mg), the opioid mu-receptor agonist alfentanil (mean dose, 11 mg), and placebo. ⋯ Appreciable symptomatic relief developed only after the onset of unpleasant drug side effects. After the infusion was stopped, pain relief disappeared before the side effects resolved. We conclude that NMDA antagonists may have promise for the treatment of neuropathic pain, but strategies are needed to improve their therapeutic ratio, such as intrathecal administration or systemic treatment with more selective drugs.