Metformin: Potential analgesic?

Objective: To determine the association of self-report use of metformin and pain intensity.

Design: Survey-based cross sectional.

Setting: Primary care in an academic medical center.

Subjects: Three hundred and twenty nine participants with diabetes.

Methods: A total of 329 men and women, aged 18-65, completed a phone-based survey. We utilized the Brief Pain Inventory to assess for pain intensity ratings; Leeds Assessment of Neuropathic Symptoms and Signs to screen for neuropathy; and the Personal Health Questionnaire (PHQ8) Depression Scale to assess for depression.

Results: Three hundred and twenty nine diabetics (mean age 54- ± 8-year old) completed the study (162 metformin users, 167 nonusers). Compared with non-users, metformin users were used more often [38% vs 20%, P = 0.001]; had lower mean depression scores [6.8 vs 8.3; P = 0.026] and fewer comorbidities [1.5 vs 1.8, P = 0.022]. Adjusting for those three variables, pain scores were not significantly different between groups. In a subset analyses of those with neuropathic pain (n = 156), there were no differences in pain scores found between groups.

Conclusions: In a clinic sample of patients with diabetes, the use of metformin at an average dose of 1,432 mg (SD = 596 mg) was not associated with lower pain scores. Given the anti-nociceptive effects of metformin in the animal models of pain, and the relative safety of metformin, future research should evaluate the effect of the higher dose of metformin as a potential analgesic.