Pilot Study to Assess the Efficacy of Botulinum Toxin B on Pain and Disability in Subjects With Acute Low Back Pain

Inclusion Criteria: * Male or female subjects, 18 to 60 years of age, active duty military, retired military or other DOD beneficiaries eligible for care at military treatment facilities. * Written informed consent and written authorization for use or release of health and research study information. * Clear history of an identifiable muscle strain or trauma preceding the onset of low back pain. * No prior history of vertebral disk disease/condition, sciatica or radiculopathy. * Normal neurological examination without evidence of radiculopathy. * Evidence of trigger point tenderness or muscle spasm upon palpation or EMG findings of muscle spasm. * History of low back pain lasting 3 to 6 weeks from the time of injury or strain. * VAS score minimum of 5 cm at time of entry into study. * Ability to follow study instructions and likely to complete all required visits. * Negative urine pregnancy test prior to the administration of study medication (for females of childbearing potential) (if applicable). Exclusion Criteria: * Age less than 18 or greater than 60. * Not active duty. * Concomitant use of aminoglycoside antibiotics, curare-like agents, or other agents that might interfere with neuromuscular function. * Any medical condition that may put the subject at increased risk with exposure to Myobloc®, including diagnosed myasthenia gravis, Eaton-Lambert syndrome, amyotrophic lateral sclerosis/motor neuron disease, neuropathy, renal stones, or any other disorder that might interfere with neuromuscular function or produce a similar type of low back pain. * Females who are pregnant, breast-feeding, or planning a pregnancy during the study, or who think that they may be pregnant at the start of the study, or females of childbearing potential who are unable or unwilling to use a reliable form of contraception during the study. * Known allergy or sensitivity to any of the components in the study medication. * Evidence of alcohol or substance abuse in 6 months prior to enrollment. * Systemic medical conditions (such as thyroid disease, hypertension, bleeding disorders, diabetes, cancers, etc.) that are not currently medically managed or controlled. * Concurrent participation in another investigational drug or device study or participation in the 30 days immediately prior to study enrollment. * Any condition or situation that, in the investigator's opinion, may put the subject at significant risk, confound the study results, or interfere significantly with the subject's participation in the study. * Significant Axis I or II diagnosis determined by a neurologist or psychiatrist in the 6 months prior to entry into the study. * Duration of low back pain \< 3 weeks or \> 6 weeks. * Thoracic or cervical spine pain in the absence of acute low back pain. * Anesthetic or corticosteroid injection to the lumbosacral spine within 8 weeks of enrollment. * Spine MRI (any region) positive for acute pathology or evidence of radiculopathy on neurological examination. * History of back surgery within one year or incomplete resolution of back pain due to a previous injury or surgery. * Subjects involved in litigation, seeking significant disability for low back pain, or with evident secondary gain as determined by the neurologist through chart review and subject interview. * Any previous use of Myobloc®, Dysport®, or BOTOX®.