[Postponed or canceled drug challenge tests and side effects of the test drug--a report of four cases].

Drug challenge test (DCT) is performed to evaluate chronic pain pharmacologically and determine its medical treatment. One test drug is administered in one day for DCT and characterization of the test drug. Four patients developed side effects of the test drugs for DCT in whom other drug tests were postponed or canceled. A 58-year-old man with multiple arthritis of rheumatic arthritis and fibromyalgia had headache, nausea, and vomiting all day after ketamine test. A 76-year-old man with chronic general pain and failed back surgery syndrome had vomiting and abdominal discomfort two hours after morphine test and had redness and itching on his bilateral forearms the following day. A 78-year-old man with chronic lumbar and right lower limb pain due to L 4-5 lumbar disc herniation and postherpetic neuralgia felt dizzy, fell down and bruised on his lower back and left knee twelve hours after morphine test. A 32-year-old woman with chronic pelvic pain had skin eruption on her thigh the day after phentolamine test. Although the amount of the test drug in DCT is small and its half-life is short, long-term side effects might occur. We should decrease the amounts or frequencies of ketamine and morphine, and administer them taking long intervals before other tests.