T J Schnitzer, W L Gray, R Z Paster, M Kamin

To evaluate the efficacy and safety of tramadol in the treatment of chronic low back pain. A 3 phase trial: (1) a washout/screening phase; (2) a 3 week, open label, run-in phase; and (3) a 4 week, randomized, placebo controlled, double blind treatment phase. Three hundred eighty outpatients between 21 and 79 years with chronic low back pain with no or a distant history of back surgery enrolled in the open label phase and were treated with tramadol up to 400 mg/day. At the end of the open label phase, patients who tolerated tramadol and perceived benefit from it were randomized to continue treatment with tramadol or to convert to placebo in the double blind phase. Reasons for discontinuing from the open label phase included adverse events, 78 patients (20.5%); drug ineffective, 23 patients (6.1%); and other reasons, 25 patients (6.6%). Two hundred fifty-four patients entered the double blind phase, during which the daily dose was maintained within the range 200-400 mg tramadol or equivalent amount of placebo. The primary outcome measure in the double blind phase was the time to discontinuation due to inadequate pain relief. The distribution of time to therapeutic failure was significantly (p < or = 0.0001) different in the tramadol group compared to placebo. Kaplan-Meier estimate of the cumulative discontinuation rate due to therapeutic failure was 20.7% in the tramadol group and 51.3% in the placebo group. There were significantly lower (p < or = 0.0001) mean pain visual analog scores (10 cm scale) among tramadol patients (3.5 cm) compared to placebo patients (5.1 cm) at the final visit of the double blind phase. Tramadol patients scored significantly better on the McGill Pain Questionnaire (p = 0.0007) and the Roland Disability Questionnaire (p = 0.0001). Five of 127 tramadol treated patients and 6/127 placebo treated patients discontinued treatment during the double blind phase due to an adverse event. Commonly reported adverse events with tramadol included nausea, dizziness, somnolence, and headache. Among patients who tolerated it well, tramadol was effective for the treatment of chronic low back pain.