The safety and efficacy of Carisoprodol for the relief of acute, idiopathic mechanical low back pain was evaluated in two, 7-day, double blind, randomized, multicenter, placebo controlled, U.S. trials (Study 1). Patients had to be 18 to 65 years old and had to have acute back pain (? 3 days of duration) to be included in the trials. Patients with chronic back pain; at increased risk for vertebral fracture (e.g., history of osteoporosis); with a history of spinal pathology (e.g., herniated nucleus pulposis, spondylolisthesis or spinal stenosis); with inflammatory back pain, or with evidence of a neurologic deficit were excluded from participation. Concomitant use of analgesics (e.g., acetaminophen, NSAIDs, tramadol, opioid agonists), other muscle relaxants, botulinum toxin, sedatives (e.g., barbiturates, benzodiazepines, promethazine hydrochloride), and anti-epileptic drugs was prohibited.
In Study 1, patients were randomized to one of three treatment groups (i.e., Carisoprodol Tablets 350 mg, or placebo). In the study patients received study medication three times a day and at bedtime for seven days.
The primary endpoints were the relief from starting backache and the global impression of change, as reported by patients, on Study Day 3. Both endpoints were scored on a 5-point rating scale from 0 (worst outcome) to 4 (best outcome) in both studies. The primary statistical comparison was between the Carisoprodol 250 mg and placebo groups in both studies.
The proportion of patients who used concomitant acetaminophen, NSAIDs, tramadol, opioid agonists, other muscle relaxants, and benzodiazepines was similar in the treatment groups.
The results for the primary efficacy evaluations in the acute, low back pain studies are presented in Table 3.
Table 3. Results of the Primary Efficacy Endpoints* in Study 1
Study Parameter Placebo Carisoprodol Tablets 350 mg
1 Number of Patients n=269 n=273
Relief for Starting Backache, Mean (SE)† 1.4(0.1) 1.8 (0.1)
Difference between Carisoprodol and Placebo, Mean (SE)† (95% CI) 0.4
(0.2,0.6)
Global Impression of Change, Mean (SE)† 1.9(0.1) 2.2 (0.1)
Difference between Carisoprodol and Placebo, Mean (SE)† (95% CI) 0.3
(0.1,0.4)
*The primary efficacy endpoints (Relief from Starting Backache and Global Impression of Change) were assessed by the patients on Study Day #3. These endpoints were scored on a 5-point rating scale from 0 (worst outcome) to 4 (best outcome).
†Mean is the least squared mean and SE is the standard error of the mean.
Patients treated with Carisoprodol experienced improvement in function as measured by the Roland-Morris Disability Questionnaire (RMDQ) score on Days 3 and 7.