Purpose: The objective of this placebo-controlled trial was to determine the efficacy and safety of carisoprodol (Soma, MedPointe Pharmaceuticals, Somerset, NJ, USA), a centrally acting skeletal muscle relaxant used to treat acute, painful musculoskeletal conditions, at a dosage of 250 mg three times daily and at bedtime in patients with acute, painful muscle spasm of the lower back.
Methods: This was a 7-day, multicenter, randomized, double-blind, placebo-controlled, parallel-group study. Qualified patients were randomly assigned to treatment with carisoprodol 250-mg tablets (n = 277) or matching placebo tablets (n = 285). The coprimary efficacy endpoints were patient-rated global impression of change and patient-rated relief from starting backache scored on a 5-point rating scale. The primary analysis was on study Day 3. Four secondary endpoints were also assessed: (1) the Roland-Morris Disability Questionnaire (RMDQ), (2) time to symptom improvement, (3) patient-rated medication helpfulness, and (4) physician assessment of range of motion.
Results: Carisoprodol was significantly more effective than placebo for patient-rated global impression of change (2.24 vs. 1.70; p < 0.0001) and patient-rated relief from starting backache (1.83 vs. 1.12; p < 0.0001). Patients experienced clinical improvement with or without sedation. Onset of moderate or marked improvement was 3 days with carisoprodol compared to 6 days with placebo (p < 0.0001). No patient discontinued treatment with carisoprodol because of drowsiness, and there were no serious adverse events or clinically significant effects on laboratory values or vital signs.
Conclusions: In this study, patients with acute muscle spasm of the lower back had significantly greater and more rapid relief from starting backache, and had improved functional status, as measured by the RMDQ, during treatment with carisoprodol 250-mg tablets compared to placebo. Patients experienced clinical improvement with or without sedation.