A study published in PAIN Practice found that in women with fibromyalgia, the use of allopurinol may not be effective as adjuvant therapy, thereby contradicting its earlier findings of analgesic effects. Allopurinol, a potent xanthine oxidase inhibitor, is used to treat hyperuricemia and gout. Considering its analgesic benefits, Aécio C Fagundes et al. hypothesized that the allopurinol could be a valid approach for the treatment of pain.

This randomized, double-blinded, placebo-controlled study compared the pain-relieving efficacy of allopurinol taken orally versus placebo as adjuvant therapy in fibromyalgia. Sixty women with fibromyalgia received either oral allopurinol 300 mg (31 patients) or placebo (29 patients) twice every day for the duration of 30 days. Their pain sensitivity, depression, anxiety, and functional status were examined prior to the therapy and, 15 and 30 days after.

Allopurinol oral 300 mg taken twice daily was ineffective in improving pain scores for up to 30 days of therapy. No significant effects of allopurinol over depressive symptoms, anxiety, and functional status were found.