Abstract
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.
Highlights
Painful diabetic neuropathy (PDN) is one of the complications of diabetes mellitus (DM) which consists of various painful sensation as a result of diffuse damage to the peripheral nerve fibers and its consequent peripheral nerve dysfunction [1,2]
The primary outcome of the study was to determine the rate of Numeric pain rating scale (NPRS) reduction between groups, before and after an intervention, whereas the secondary outcome was to determine the onset of NPRS reduction and its sustainability over time
The majority of patients in the treatment group was on insulin therapy, whereas the proportion of those with oral hypoglycemic drugs and insulin in the control group was comparable
Summary
PDN is one of the complications of diabetes mellitus (DM) which consists of various painful sensation (burning, painful cold, electric shocks) as a result of diffuse damage to the peripheral nerve fibers and its consequent peripheral nerve dysfunction [1,2]. There has been limited treatment modalities with high efficacy and sustainable improvement in PDN. MeCbl is considered the best form of vitamin B12 for nerve because of its high concentration in the CSF (constituting 90% of total cobalamin in the CSF) and higher uptake by neuronal organelles [8,9]. MeCbl ameliorates neuropathic pain via multiple mechanisms, including promoting axonal regeneration, protecting against glutamate-induced neurotoxicity, and inhibiting ectopic spontaneous discharge [7,10,11]. MeCbl has been effective in ameliorating neuropathic pain from various pathologies, including sciatica, herpetic, glossopharyngeal, and trigeminal neuralgia [7]. MeCbl for the treatment of DN has been studied in multiple trials with mixed results, and only a few targeted PDN [8,12,13]
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