The purpose of this study is to determine if two sustained released formulations of carisoprodol are more effective than placebo.

Methodology:

This was a randomized, double-blind, double-dummy, placebo-controlled, parallel-group study in subjects 18-70 years of age with acute, painful, muscle spasm of the lower back. The study consisted of a baseline screening (Study Day 1), during which subjects were evaluated for inclusion/exclusion criteria, and a 7-day double-blind treatment period (Study Day 1 through Study Day 7). Subjects were randomly assigned to be dosed twice daily with one of the following double-blind treatments: sustained release(SR) carisoprodol 500-mg tablets,sustained release (SR) carisoprodol 700-mg tablets, or placebo.

Subjects were evaluated in the clinic on Study Days 1, 3 and 7. Subjects who remained symptomatic on Study Day 7 were allowed to continue in the study for a 7-day, double-blind extension period at the discretion of the Investigator. Subjects were contacted by telephone for a safety follow-up 7 days after the last dose of study medication.

A pharmacokinetic (PK) substudy was conducted at selected sites. These sites obtained blood samples for PK analysis at the end of the 7-day treatment period and the 14-day treatment period, if applicable.

Inclusion Criteria:

• Onset of pain is within 3 days of first visit
• Subject rating of pain must be 40 mm or greater on visual analog scale( VAS)
• Ability to discontinue all analgesics, non steroidal anti inflammatory drug (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 nucleas pulposis, spondylolisthesis, spinal stenosis
• Presence of underlying chronic back pain
• Neurological signs and symptoms such as numbness, tingling, foot drop, parethesia, unexplained constipation, urinary retention or urinary incontinence
• Myocardial infaction 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 vetebral fracture
• Underlying rheumatologic disease such as rheumatoid arthritis, ankylosing spondylitis, etc.
• Presence of active influenze or other viral syndromes
• Morbid obesity basal metabolic index(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 hypereflexic 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