Amitriptyline for fibromyalgia - 2008 update
Clinical bottom line
There is evidence of limited size and quality that amitriptyline 25 mg daily is effective in fibromyalgia.
Reference
Nishishinya et al. Amitriptyline in the treatment of fibromyalgia: a systematic review of its efficacy. Rheumatology 2008 Epub.
Study
- Date review completed: 2007
- Number of trials included: 10
- Number of patients: 615
- Control group: placebo
- Main outcomes: various
Results
Four randomised, double blind trials comparing amitriptyline 50 mg with placebo, two of four weeks' duration and the others of nine and 24 weeks, failed to find any difference between them for any outcome.
Six randomised, double blind trials comparing amitriptyline 25 mg with placebo found consistent improvements for patient global assessment, pain, sleep, and fatigue in trials of six or eight weeks, but no effect in a trial lasting 12 weeks.
Comment
The ators conclude that 50 mg of amitriptyline daily is ineffective in fibromyalgia, and that 25 mg daily is effective only up to about eight weeks. The idea of a reverse dose-response with less benefit with higher doses of amitriptyline is difficult to explain, there is good evidence for effect of 25 mg daily. Trying to conclude that the effects of 25 mg daily are only short term pusheds the evidence too far - based on a single trial with a large (almost 30%) loss of patients.
If we should be concerned it is about small trials that frequently had large loss of follow up (half lost more than 10% of patients), but that generally did not perform an intention to treat analysis. Only three did so. This should concern us about the positive and the negative results.