A drug that inhibits NMDA receptors (such as ketamine, a surgical
anesthetic) is continuously administered to patients suffering from
neuropathic pain. Unless the NMDA antagonist drug has inherent safening
activity, this treatment requires a "safener" drug to prevent the
neurotoxic side effects of NMDA antagonists. One class of safener drugs
that increase the efficacy of the treatment include alpha-2 adrenergic
agonists, such as clonidine. The treatment lasts for several days and
nights, continuously. A maximum tolerated dosage is titered for each
patient, such as by observing slurring of speech, and the patient does
not lose consciousness except during normal sleep. Magnesium and/or drugs
that inhibit ketamine-degrading enzymes can also be used. Patients who
suffered for years from chronic intractable pain emerged from this
treatment with apparently permanent relief, or with lasting reductions in
their levels of pain.
