A Cochrane review included 14 RCTs with a total of 364 patients with muscle disease. They were given creatine with doses ranging from 3 to 20 g daily. Meta-analysis of 6 trials (n=192) in muscular dystrophies with follow-up periods ranging from 8 weeks to 6 months revealed a significant increase in muscle strength in the creatine group compared to placebo, with a weighted mean difference of 8.47% (95% CI 3.55 to 13.38). Pooled data of 4 trials (n=115) showed that a significantly higher number of patients with muscle dystrophies felt better during creatine treatment compared to placebo with a risk ratio of 4.51 (95% CI 2.33 to 8.74). One trial in 37 participants with idiopathic inflammatory myopathies also showed a significant improvement in functional performance. No trial reported any clinically relevant adverse event. In metabolic myopathies, meta-analyses of 3 cross-over trials (n=33) revealed no significant difference in muscle strength. One trial of McArdle disease (n=19) reported a significant deterioration of activities of daily living (mean difference 0.54 on a 1 to 10 scale; 95% CI 0.14 to 0.93) and an increase in muscle pain during high-dose creatine treatment.
Comment: The quality of the evidence is downgraded by imprecise results (limited study size for each comparison).