Comment: The quality of evidence is downgraded by study quality (unclear allocation concealment and blinding), by inconsistency (heterogeneity in interventions and outcomes), and by imprecise results (limited study size for each comparison).
A Cochrane review [Abstract] 1 included 22 studies with a total of 1 278 subjects covering 13 herbal interventions (4 of which were combination products). Evidence from 7 studies indicates potential benefits of gamma linolenic acid (GLA) from evening primrose oil, borage seed oil, or blackcurrent seed oil, in terms of reduced pain intensity (MD -32.83 points, 95% CI -56.25 to -9.42, 100 point pain scale; 3 studies, n=82) and improved disability (MD -15.75%, 95% CI -27.06 to -4.44%; 1 study, n=41). An increase in adverse events was observed (GLA 20% versus placebo 3%) but that was not statistically significant (RR 4.24, 95% CI 0.78 to 22.99; 2 studies, n=61).
Three studies compared Tripterygium wilfordii (thunder god vine) to placebo and one to sulfasalazine and indicated improvements in some outcomes, but data could not be pooled due to differing interventions, comparisons and outcomes. One study reported serious side effects with oral Tripterygium wilfordii Hook F. In the follow-up studies, all side effects were mild to moderate and resolved after the intervention ceased. Two studies compared Phytodolor® N to placebo but poor reporting limited data extraction. The remaining studies each considered differing herbal interventions.
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