A Two-Arm Study Comparing the Analgesic Efficacy and Safety of Acetaminophen and Tramadol Combination BID Versus Placebo for the Treatment of Acute Low Back Pain

Inclusion Criteria: * Males or females in generally good health aged 18-80 years with moderate to severe acute low back pain. * Current acute low back pain episode within 48h prior to study entry. * Pain must be moderate to severe following incident Exclusion Criteria: * Chronic low back pain * Ongoing or history of alcohol or drug abuse * Body Mass Index greater 39 * Treatment within the last 3 weeks with monoamine oxidase inhibitors; tricyclic antidepressants and other tricyclic compounds; neuroleptics; selective serotonin reuptake inhibitors * Known history or symptoms suspicious for cancer * Significant renal or liver disease * Spinal surgery within 1 year of study entry. * Subjects who are pregnant or lactating. * Subjects with unstable medical disease. * Subjects who have received treatment with an investigational product/device with 30 days prior to study entry.