Effects of creatine supplementation on muscle weakness in patients with rheumatoid arthritis

Background and objectives. Patients with rheumatoid arthritis (RA) frequent ly suffer from muscle weakness. Oral administration of creatine has been sh own to improve muscle strength in healthy subjects. The objective of this s tudy was to examine the effect of oral creatine supplementation on muscle w eakness, disease activity and activities of daily living in patients with R A. Methods. During a period of 3 weeks, 12 patients with RA were treated with creatine monohydrate (20 g/day For 5 days followed by 2 g/day for 16 days). They were examined on entry and at the end of the study. The patients were investigated clinically, blood and urine samples were obtained, muscle bio psies were performed before and after treatment, muscle strength was determ ined, and self-administered patient questionnaires were completed. Results. From all patients we were able to obtain full clinical and questio nnaire data, while biopsies were taken from 12 patients at the start and fr om nine patients at the end of the study. Muscle strength, as determined by the muscle strength index, increased in eight of 12 patients. In contrast, physical functional ability and disease activity did not change significan tly. The creatine concentration in serum and skeletal muscle increased sign ificantly, while creatine phosphate and total creatine did not increase in skeletal muscle. The skeletal muscle creatine content was associated with m uscle strength at baseline but not after administration of creatine. The ch anges in muscle strength were not associated with the changes in skeletal m uscle creatine or creatine phosphate. Conclusion. Although the skeletal muscle creatine content and muscle streng th increased with creatine administration in some patients with RA, a clear clinical benefit could not be demonstrated for this treatment when the pat ients were considered as one group.