Intravenous methylcobalamin effectively ameliorated painful diabetic neuropathy: A randomized double-blind placebo controlled trial

Objective. Painful diabetic neuropathy (PDN) is a prevalent debilitating consequence of diabetes mellitus with lack of satisfactory therapeutic options. Methylcobalamin (MeCbl) is one of vitamin B12 analogs with known neurotrophic effects. We aimed to determine if MeCbl can relieve PDN. Materials and methods. This was a randomized (1:1) double-blind placebo-controlled trial involving PDN patients. Treatment and control group received daily 12.5 mg oral amitriptyline bid with either 500 µg of intravenous MeCbl or saline injection given on alternating days, respectively, for a 9-consecutive day period. PDN was assessed with douleur neuropathique 4 (DN4) questionnaire. Numeric pain rating scale (NPRS) was used to monitor pain intensity and treatment response. All investigators and patients were kept blinded throughout the study period. Outcomes. 42 patients, 21 on each arm had completed the study. The NPRS reduction can already be observed as early as day 2 post-intervention. Both the treatment and control group demonstrated sustained reduction of NPRS by almost one point per each time point of evaluation in the first three days (p<0.001). NPRS reduction remained until the end of the study period. The treatment group had a significantly lower NPRS score by 1.29 than that of the control group during the entire study period (95% CI -1.84 – -0.75; p < 0.001). Treatment group experienced significantly higher NPRS reduction when compared with control (4.19±1.54 vs. 2.1± 0.83; 95% CI 1.32-2.87; p < 0.001), i.e. 62.6% from baseline. Conclusions. MeCbl significantly and safely relieved PDN in a relatively rapid onset.