Study to Evaluate Two Formulations of Carisoprodol in Subjects With Musculoskeletal Spasm of the Lower Back

Inclusion Criteria: * Onset of pain is within 3 days of first visit * Subject rating of pain must be 40 mm or greater on VAS * Ability to discontinue all analgesics, NSAIDs, and other muscle relaxants * Willingness to provide written informed consent * Must be in generally good health Exclusion Criteria: * Presence of sciatic pain * History of clinically significant spine pathology such as herniated nucleus pulpous, spondylolisthesis, spinal stenosis * Presence of underlying chronic back pain * Neurological signs and symptoms such as numbness, tingling, foot drop, paresthesia, unexplained constipation, urinary retention or urinary incontinence * Myocardial infarction within one year of study * Cancer not in remission or in remission less than one year * HIV or other immunodeficiency syndromes * History of osteoporosis or at high risk for vertebral fracture * Underlying rheumatologic disease such as rheumatoid arthritis, ankylosing spondylitis, etc. * Presence of active influenza or other viral syndromes * Morbid obesity (BMI \>39) * Evidence of infection, such as low grade fever or neutrophilia * Existence of any medical/surgical condition that could interfere with the evaluation of the study medication * Known history of alcohol or drug abuse * Injury involving high potential for litigation, including worker's compensation or automobile accidents * Pregnancy or breast feeding * Women of child-bearing potential not abstinent or not practicing a medically acceptable method of contraception * Vertebral body or spinous process, percussive tenderness on physical exam * Any abnormalities in the following tests of both lower extremities: ankle dorsiflexion strength, great toe dorsiflexion strength, absent or hyperreflexic Achilles or patellar tendor reflexes, abnormal sensory exam in the medial, dorsal or lateral aspect of the foot and positive straight leg raise test * Urgent medical conditions on comprehensive exam that might indicate a more serious condition should be treated urgently