Ketamine IV in outpatient setting: effective treatment for neuropathic pain syndromes

Ketamine is an antagonist of NMDA-type glutamate receptors, These play a strong promoting role in pain transmission in the CNS, in sub-anesthetic doses. We have also used this for migraines and headaches. This is an ongoing study of this agent for treating pain flareups in neuropathic pain syndromes. 389 patients (264=f, 125=m) were treated for pain flareups. All had allodynia or hyperalgesia in the region of pain, Conditions treated were: CRPS (n=126), cervical/lumbar radiculopathy (n=145), TN (n=34), TMD (n=47), pelvic/vulvodynia pain (n=37). 285 patients had co-existent headache/migraine. Antecubital IV was placed; pulse oximetry monitoring was used in each patient. Patients rated their pain on a 0-10 VAS both before treatment and at 15 minute intervals during and after treatment. 0.25-0.30 mg ketamine/kg was administered by IV infusion over 120-180 minutes. Another 0.30 mg/kg, or slightly higher dose ,was administered again over the same time. Up to 4 infusions were given, not necessarily on the same day. We defined success as greater than 50% reduction in pain VAS from baseline. Beginning pain (8.45/10) reduced to 2.03/10 after treatment (p< .001, 2 tailed t test). Average ketamine infusion time was 149 min; average ketamine dose was 185.6mg. Time of pain reduction was 4.4 days (range = 26 hrs to 233 hrs). Side effects were transient spaciness/calm (n=344). Allodynia was gone in all but 2 patients. 12 patients reported less than 25% reduction in pain. 271 patients reported better than 50% decrease in headache. Our data supports NMDA-type glutamate receptor over-activity in many neuropathic pain disorders, with great efficacy, safety and tolerability for the treatment.