RESUMEN
BACKGROUND: This study evaluated the safety and efficacy of tramadol ER 300 mg and 200 mg versus placebo once daily in the treatment of chronic low back pain, using an open-label run-in followed by, without washout, a randomized controlled study design. METHODS: Adults with scores > or = 40 on a pain intensity visual analog scale (VAS; 0 = no pain; 100 = extreme pain) received open-label tramadol ER, initiated at 100 mg once daily and titrated to 300 mg once daily during a three-week open-label run-in. Patients completing run-in were randomized to receive tramadol ER 300 mg, 200 mg, or placebo once daily for 12 weeks. RESULTS: Of 619 patients enrolled, 233 (38 percent) withdrew from the run-in, primarily because of adverse event (n = 128) or lack of efficacy (n = 41). A total of 386 patients were then randomized to receive either 300 mg (n = 128), 200 mg (n = 129), or placebo (n = 129). Following randomization, mean scores for pain intensity VAS since the previous visit, averaged over the 12-week study period, increased more in the placebo group (12.2 mm) than in the tramadol ER 300-mg (5.2 mm, p = 0.009) and 200-mg (7.8 mm, p = 0.052) groups. Secondary efficacy scores for current pain intensity VAS, patient global assessment, Roland Disability Index, and overall sleep quality improved significantly (p < or = 0.029 each) in the tramadol ER groups compared with placebo. The most common adverse events during the double-blind period were nausea, constipation, headache, dizziness, insomnia, and diarrhea. CONCLUSIONS: In patients who tolerated and obtained pain relief from tramadol ER, continuation of tramadol ER treatment for 12 weeks maintained pain relief more effectively than placebo. Adverse events were similar to those previously reported for tramadol ER.