We studied intravenous (IV) ketamine in an outpatient headache/pain clinic to treat refractory migraines with and without aura (RM), chronic daily headaches (CDH), cluster headaches (CH), paroxysmal hemicrania (PH) and migraine/face pain headache subtypes (MFP). Ketamine is an antagonist of NMDA-type glutamate receptors, known to play a role in pain transmission. Little data exists on this receptor subtype in migraine/headache pathophysiology and treatment. This is an open-label study. 247 (191=f, 56=m) patients were treated. 175 patients with RM, 11 with CH, 4 with PH, 39 with CDH, 18 with MFP. 490 ketamine infusions were administered. 0.25-0.3 mg ketamine/kg was administered over 90-120 minutes. 151 patients received a second ketamine infusion and 92 patients received a 3rd. Patients rated their pain on 0-10 VAS every 15 minutes. Beginning pain severity was 7.14/10 VAS; it reduced to 2.15/10 VAS after treatment (p<.001, 2 tailed t-test). Infusion time was 188 min and the average dose of ketamine was 95.6 mg. 6 patients (of 247 treated) had no (or less than 50%) response to IV ketamine with up to 3 treatments. All patients with allodynia (n=224) reported total abolishment by IV ketamine. Side effects were: transient spaciness during 299 of 490 infusions. 8 patients got slightly agitated and there were no hallucinations or dysphoric symptoms. This is a clinical description of successful treatment for multiple types of RM, CH, PH, CDH and MFP variants with IV ketamine. This is a very effective new form of treatment with implications for migraine and pain pathophysiology and is efficacious and tolerated well, with proper monitoring, in an outpatient headache clinic. It has minimal transient side effects and toxicity in subanesthetic doses. IV ketamine should be studied in a double-blind fashion in the treatment of pain and migraines, and other primary headaches.
© 2010 American Pain Society. Published by Elsevier Inc. All rights reserved.