Pharmacological classification of intractable chronic pain (drug challenge tests)]

Intractable chronic pain resists any therapy, and the mechanism of the pain varies from patient to patient even with the same disease. Therefore, patients with chronic pain tend to look for a doctor who would successfully attenuate their pain. Consequently, a patient may visit several doctors only to get similar treatments after wasting time and money. To avoid the situation, pharmacological classification (so called drug challenge test) to determine the mechanism of a patient's pain is conducted. Drugs tested are morphine, ketamine, lidocaine, thiopental, phentolamine, midazolam, ATP clomipramine, PGE1, and neurotropin. A test for each drug is conducted on a separate day. As each drug has a different pain-attenuating mechanism, mechanism of a patient's pain will be clarified when an effective drug is found. A drug is administered as a bolus several times or continuously intravenously. According to the results of our tests conducted in sixty-five patients with neuropathic pain due to peripheral nerve injuries, ketamine proves to be the most effective in alleviating pain followed by ATP, morphine and thiopental. Therapies based on the results were provided to the patients.