Neuropathy and Neuropathic Pain in Patients with Type 2 Diabetes Mellitus Receiving Metformin - A Cross-Sectional Study from Navi Mumbai, Maharashtra

BACKGROUND Metformin is reported to induce vitamin B12 deficiency and distinguishing peripheral neuropathy due to vitamin B12 deficiency from diabetic peripheral neuropathy can be challenging. The present study was conducted to assess and compare the clinical presentation of diabetic patients taking metformin with those not taking metformin using Toronto clinical scoring system (TCSS). METHODS This cross-sectional study included 60 patients with diabetes mellitus, 30 patients on metformin therapy (at least 6 months) and 30 patients not on metformin use. Clinical presentation of the patients was assessed using the TCSS. Patients were diagnosed according to the American diabetic association criteria. RESULTS The mean age of the patients in metformin and non-metformin group was 57.27 ± 9.38 and 58.63 ± 10.27 years respectively. Gender distribution was observed to be similar in both the study groups. Mean duration of diabetes mellitus was found to be similar in both the study groups (5.4 ± 1.01 vs 5.2 ± 1.27 years) and duration of peripheral neuropathy was also found to be similar in the two study groups (3.2 ± 1.6 vs 3.3 ± 1.5 years). Numbness was observed in maximum number of cases in both study groups. It was seen in 100 % (n = 30) patients on metformin drug while in 90 % (n = 27) patients without metformin. Pain accounts to be approximately 77 % (n = 23) and 24 % (n = 7) in patients on metformin and without metformin. Neuropathic symptoms and neuropathic reflex scoring appear to be higher common in patients on metformin as compared to those without metformin. Mean pain score was found to be significantly higher among patients on metformin as compared to those not on metformin (8.43 ± 2.13 vs 4.03 ± 3.13; P value < 0.001). CONCLUSIONS Our results show that patients on metformin for diabetes mellitus experience higher neuropathic symptoms as compared to those not taking metformin. KEYWORDS Diabetes Mellitus, Metformin, Peripheral Neuropathy, Vitamin B12