Clinical Trial Assessing the Efficacy of Gabapentin Plus B Complex (B1/B12) versus Pregabalin for Treating Painful Diabetic Neuropathy

Diabetic peripheral neuropathy: pathogenetic mechanisms and treatment

Diabetic peripheral neuropathy (DPN) refers to the development of peripheral nerve dysfunction in patients with diabetes when other causes are excluded. Diabetic distal symmetric polyneuropathy (DSPN) is the most representative form of DPN. As one of the most common complications of diabetes, its prevalence increases with the duration of diabetes. 10-15% of newly diagnosed T2DM patients have DSPN, and the prevalence can exceed 50% in patients with diabetes for more than 10 years. Bilateral limb pain, numbness, and paresthesia are the most common clinical manifestations in patients with DPN, and in severe cases, foot ulcers can occur, even leading to amputation. The etiology and pathogenesis of diabetic neuropathy are not yet completely clarified, but hyperglycemia, disorders of lipid metabolism, and abnormalities in insulin signaling pathways are currently considered to be the initiating factors for a range of pathophysiological changes in DPN. In the presence of abnormal metabolic factors, the normal structure and function of the entire peripheral nervous system are disrupted, including myelinated and unmyelinated nerve axons, perikaryon, neurovascular, and glial cells. In addition, abnormalities in the insulin signaling pathway will inhibit neural axon repair and promote apoptosis of damaged cells. Here, we will discuss recent advances in the study of DPN mechanisms, including oxidative stress pathways, mechanisms of microvascular damage, mechanisms of damage to insulin receptor signaling pathways, and other potential mechanisms associated with neuroinflammation, mitochondrial dysfunction, and cellular oxidative damage. Identifying the contributions from each pathway to neuropathy and the associations between them may help us to further explore more targeted screening and treatment interventions.

Mechanisms of action of vitamin B1 (thiamine), B6 (pyridoxine), and B12 (cobalamin) in pain: a narrative review

Pain is a complex sensory and emotional experience with nociceptive, nociplastic, and neuropathic components. An involvement of neurotropic B vitamins (B1 - thiamine, B6 - pyridoxine, and B12 - cyanocobalamin) as modulators of inflammation and pain has been long discussed. New evidence suggests their therapeutic potential in different pain conditions. In this review, we discuss the main role of neurotropic B vitamins on different nociceptive pathways in the nervous system and to describe their analgesic action mechanisms. The performed literature review showed that, through different mechanisms, these vitamins regulate several inflammatory and neural mediators in nociceptive and neuropathic pain. Some of these processes include aiming the activation of the descending pain modulatory system and in specific intracellular pathways, anti-inflammatory, antioxidative and nerve regenerative effects. Moreover, recent data shows the antinociceptive, antiallodynic, and anti-hyperalgesic effects of the combination of these vitamins, as well as their synergistic effects with known analgesics. Understanding how vitamins B1, B6, and B12 affect several nociceptive mechanisms can therefore be of significance in the treatment of various pain conditions.

A Latin American consensus meeting on the essentials of mixed pain

OBJECTIVES

The term "mixed pain" has been established when a mixture of different pain components (e.g. nociceptive, neuropathic, and nociplastic) are present. It has gained more and more acceptance amongst pain experts worldwide, but many questions around the concept of mixed pain are still unsolved. The sensation of pain is very personal. Cultural, social, personal experiences, idiomatic, and taxonomic differences should be taken into account during pain assessment. Therefore, a Latin American consensus committee was formed to further elaborate the essentials of mixed pain, focusing on the specific characteristics of the Latin American population.

METHODS

The current approach was based on a systematic literature search and review carried out in Medline. Eight topics about the definition, diagnosis, and treatment of mixed pain were discussed and voted for by a Latin American consensus committee and recommendations were expressed.

RESULTS

At the end of the meeting a total of 14 voting sheets were collected. The full consensus was obtained for 21 of 25 recommendations (15 strong agreement and 6 unanimous agreement) formulated for the above described 8 topics (7 of the 8 topics had for all questions at least a strong agreement - 1 topic had no agreement for all 4 questions).

CONCLUSION

In a subject as complex as mixed pain, a consensus has been reached among Latin American specialists on points related to the definition and essence of this pain, its diagnosis and treatment. Recommendations for diagnosis and treatment of mixed pain in Latin America were raised.

Gabapentinoids for Pain: A Review of Published Comparative Effectiveness Trials and Data Submitted to the FDA for Approval

Use of the gabapentinoids for pain continues to increase. In 2018, the US Food and Drug Administration (FDA) strengthened the warnings for both gabapentin and pregabalin to emphasize the central nervous system side effects and the risk of respiratory depression, especially when combined with other centrally acting drugs. We reviewed the published comparative effectiveness literature for gabapentinoids for pain as well as all trials (published and unpublished) used by the FDA for the approval of the five pain indications for these agents (one for gabapentin, four for pregabalin). Among the findings of interest are the fact that the FDA rejected the application for gabapentin for diabetic peripheral neuropathy based on the risk versus benefit profile of that drug in the clinical trials that were submitted by the manufacturer. Additionally, both the comparative effectiveness trials as well as the studies used by the FDA tend to be short in duration and show only modest pain benefits for the gabapentinoids. The placebo response in these trials was frequently one-third to one-half as great as the pain benefit demonstrated by the gabapentinoid. Based on the available clinical trial evidence, we feel prescribers should be cautious when using gabapentinoids for pain, particularly when using these agents for a prolonged period or when combined with other, centrally acting agents.

The Effect of Neuromodulatory Drugs on the Intensity of Chronic Pelvic Pain in Women: A Systematic Review

OBJECTIVE

 To evaluate the effect of neuromodulatory drugs on the intensity of chronic pelvic pain (CPP) in women.

DATA SOURCES

 Searches were carried out in the PubMed, Cochrane Central, Embase, Lilacs, OpenGrey, and Clinical Trials databases.

SELECTION OF STUDIES

 The searches were carried out by two of the authors, not delimiting publication date or original language. The following descriptors were used: chronic pelvic pain in women OR endometriosis, associated with MESH/ENTREE/DeCS: gabapentinoids, gabapentin, amitriptyline, antidepressant, pregabalin, anticonvulsant, sertraline, duloxetine, nortriptyline, citalopram, imipramine, venlafaxine, neuromodulation drugs, acyclic pelvic pain, serotonin, noradrenaline reuptake inhibitors, and tricyclic antidepressants, with the Boolean operator OR. Case reports and systematic reviews were excluded.

DATA COLLECTION

 The following data were extracted: author, year of publication, setting, type of study, sample size, intervention details, follow-up time, and results.

DATA SYNTHESIS

 A total of 218 articles were found, with 79 being excluded because they were repeated, leaving 139 articles for analysis: 90 were excluded in the analysis of the titles, 37 after reading the abstract, and 4 after reading the articles in full, and 1 could not be found, therefore, leaving 7 articles that were included in the review.

CONCLUSION

 Most of the studies analyzed have shown pain improvement with the help of neuromodulators for chronic pain. However, no improvement was found in the study with the highest statistical power. There is still not enough evidence that neuromodulatory drugs reduce the intensity of pain in women with CPP.

Xiaoketongbi Formula vs pregabalin for painful diabetic neuropathy: A single-center, randomized, single-blind, double-dummy, and parallel controlled clinical trial

BACKGROUND

We assessed the efficacy and safety of the Xiaoketongbi Formula (XF) vs. pregabalin in patients with painful diabetic neuropathy (PDN).

METHODS

Patients with PDN (n = 68) were included in a single-center, randomized, single-blind, double-dummy, parallel controlled clinical trial. The primary outcome was the change in the Brief Pain Inventory for Diabetic Peripheral Neuropathy (BPI-DPN). Secondary outcomes evaluated included the reduction of BPI-DPN >50%, changes in the numeric rating scale-11 (NRS-11) score for pain, Daily Sleep Interference Diary (DSID), Patient Global Impression of Change (PGIC), nerve conduction velocity (NCV), and adverse events.

RESULTS

After 10 weeks of treatment, the BPI-DPN score reduced from 42.44 ± 17.56 to 26.47 ± 22.22 and from 52.03 ± 14.30 to 37.85 ± 17.23 in the XF and pregabalin group (Ps  < 0.001), respectively. The difference in the absolute change in BPI-DPN score between both groups was -1.79 (95% CI: -9.09, 5.50; p = 0.625). In the XF and pregabalin groups, 44.1% (15/34) and 20.6% (7/34) of patients reported a BPI-DPN reduction >50% (p = 0.038), respectively. There were no significant differences between groups in NRS-11 and DSID (Ps  > 0.05). A significantly greater number of patients in the XF group felt "significantly improved" or "improved" than in the pregabalin group (35.3% (12/34) vs. 11.8% (4/34), p = 0.045). The absolute change in motor nerve conduction velocity of the right median nerve was significantly different between both groups (XF group 0.7 ± 2.3 vs. pregabalin group -2.2 ± 4.1, p = 0.004). No serious adverse events were reported in either group.

CONCLUSIONS

XF is equivalent to pregabalin in reducing pain symptoms and improves the quality of life in patients with PDN. In addition, XF has the potential to improve nerve function by increasing NCV.

Comparing pregabalin and gabapentin for persistent neuropathic pain: A protocol for a pilot N-of-1 trial series

Background

Evidence-based management of neuropathic pain is commonly ineffective due to the large variability in response between cases. Patients often have to trial several drugs before finding one that provides adequate relief, leading to increased costs and worsened outcomes. There is thus a need for tools to guide and streamline prescribing decisions in neuropathic pain. N-of-1 trials provide a potentially precise and economical method of selecting between multiple interventions in an individual patient, and merit a feasibility assessment for use in clinical pain practice.

Aims

We aim to evaluate the feasibility of N-of-1 trials to compare pregabalin and gabapentin for individual presentations of neuropathic pain.

Methods

This is a double-blinded multiple crossover study, with recruitment from existing patients at an outpatient pain clinic in New South Wales, Australia. Participants will undergo three 4-week treatment pairs, comprising 2 weeks of pregabalin (150–600 mg/day) and 2 weeks of gabapentin (900–3600 mg/day), in an individually randomised order. Intervention doses will be derived from participants’ existing treatment dose. Medications will be taken orally three times daily. The primary outcome will be pain intensity; measures will be self-reported daily in patient diaries. After completing all three cycles, participants and their physicians will be presented with the results of the trial to form an informed decision about their treatment.

Discussion

As a stable yet debilitating condition, neuropathic pain is especially amenable to an N-of-1 study design. A successful trial would represent a significant quality of life improvement for the patient, possibly extending over the course of their lifetime.

[Role of B vitamins, thiamine, pyridoxine, and cyanocobalamin in back pain and other musculoskeletal conditions: a narrative review]

Low back pain, as well as other musculoskeletal disorders (neck pain, osteoarthritis, etc.), are a very frequent cause of consultation both in primary care and in other hospital specialties and are usually associated with high functional and work disability. Acute low back pain can present different nociceptive, neuropathic and nonciplastic components, which leads to consider it as a mixed type pain. The importance of the concept of mixed pain is due to the fact that the symptomatic relief of these pathologies requires a multimodal therapeutic approach to various pharmacological targets. The antinociceptive role of the B vitamin complex has been recognized for several decades, specifically the combination of Thiamine, Pyridoxine and Cyanocobalamin (TPC). Likewise, there is accumulated evidence that indicates an adjuvant analgesic action in low back pain. The aim of the present review is to present the existing evidence and the latest findings on the therapeutic effects of the TPC combination in low back pain. Likewise, some of the most relevant mechanisms of action involved that can explain these effects are analyzed. The reviewed evidence indicates that the combined use of PCT has an adjuvant analgesic effect in mixed pain, specifically in low back pain and other musculoskeletal disorders with nociceptive and neuropathic components. This effect can be explained by an anti-inflammatory, antinociceptive, neuroprotective and neuromodulatory action of the TPC combination on the descending pain system.

Considerations for single- versus multiple-drug pharmacotherapy in the management of painful diabetic neuropathy

INTRODUCTION

The efficacy of monotherapy to reduce pain from diabetic peripheral neuropathy (DPN) is frequently not satisfactory and guidelines do not provide unanimous treatment options. In this context, multiple drug pharmacotherapy may provide benefit.

AREAS COVERED

The aim of the present review is to describe the clinical trials addressing the pharmacotherapy of painful DPN. Studies discussing efficacy and tolerability of pharmacological agents that were assessed in monotherapy and in combination treatment are reported and discussed.

EXPERT OPINION

Several clinical trials have reported benefit of multiple-drug pharmacotherapy. Nevertheless, untoward effects of combination treatment are of concern. Importantly, some trials were restricted to comparison with placebo and other compared only with active comparator(s). Only limited clinical trials assessed selected cohorts of individuals experiencing different stages of painful DPN. Despite current limitations, some evidence of studies implicating a comparison to all active comparators points to safety and effectiveness of the combination of oxycodone with pregabalin and that of pregabalin with the 5% lidocaine plaster but future, clear-cut studies are required to drive evidence-based decisions in the clinical setting.

Vitamin B12 Supplementation in Diabetic Neuropathy: A 1-Year, Randomized, Double-Blind, Placebo-Controlled Trial

AIM

To investigate the effect of normalizing vitamin B12 (B12) levels with oral B12 (methylcobalamin) 1000 μg/day for one year in patients with diabetic neuropathy (DN).

PATIENTS AND METHODS

In this prospective, double-blind, placebo-controlled trial, 90 patients with type 2 diabetes on metformin for at least four years and both peripheral and autonomic DN were randomized to an active treatment group (n = 44) receiving B12 and a control group (n = 46) receiving a placebo. All patients had B12 levels less than 400 pmol/L. Subjects underwent measurements of sural nerve conduction velocity (SNCV), sural nerve action potential (amplitude) (SNAP), and vibration perception threshold (VPT), and they performed cardiovascular autonomic reflex tests (CARTs: mean circular resultant (MCR), Valsalva test, postural index, and orthostatic hypotension). Sudomotor function was assessed with the SUDOSCAN that measures electrochemical skin conductance in hands and feet (ESCH and ESCF, respectively). We also used the Michigan Neuropathy Screening Instrument Questionnaire and Examination (MNSIQ and MNSIE, respectively) and questionnaires to evaluate quality of life (QoL) and level of pain (pain score).

RESULTS

B12 levels increased from 232.0 ± 71.8 at baseline to 776.7 ± 242.3 pmol/L at follow-up, p < 0.0001, in the active group but not in the control group. VPT, MNSIQ, QoL, pain score, SNCV, SNAP, and ESCF significantly improved in the active group (p < 0.001, p = 0.002, p < 0.0001, p < 0.000, p < 0.0001, p < 0.0001, and p = 0.014, respectively), whereas CARTS and MNSIE improved but not significantly. MCR, MNSIQ, SNCV, SNAP, and pain score significantly deteriorated in the control group (p = 0.025, p = 0.017, p = 0.045, p < 0.0001, and p < 0.0001, respectively).

CONCLUSIONS

The treatment of patients with DN with 1 mg of oral methylcobalamin for twelve months increased plasma B12 levels and improved all neurophysiological parameters, sudomotor function, pain score, and QoL, but it did not improve CARTS and MNSIE.

B12 as a Treatment for Peripheral Neuropathic Pain: A Systematic Review

Neuropathic pain describes a range of unpleasant sensations caused by a lesion or disease of the somatosensory nervous system. The sensations caused by neuropathic pain are debilitating and improved treatment regimens are sought in order to improve the quality of life of patients. One proposed treatment for neuropathic pain is vitamin B12, which is thought to alleviate pain by a number of mechanisms including promoting myelination, increasing nerve regeneration and decreasing ectopic nerve firing. In this paper, the evidence for B12 as a drug treatment for neuropathic pain is reviewed. Twenty four published articles were eligible for inclusion in this systematic review in which a range of treatment regimens were evaluated including both B12 monotherapy and B12 in combination with other vitamins or conventional treatments, such as gabapentinoids. Overall, this systematic review demonstrates that there is currently some evidence for the therapeutic effect of B12 in the treatment of post-herpetic neuralgia (level II evidence) and the treatment of painful peripheral neuropathy (level III evidence).

High-frequency spinal cord stimulation at 10 kHz for the treatment of painful diabetic neuropathy: design of a multicenter, randomized controlled trial (SENZA-PDN)

BACKGROUND

Painful diabetic neuropathy (PDN), a debilitating and progressive chronic pain condition that significantly impacts quality of life, is one of the common complications seen with long-standing diabetes mellitus. Neither pharmacological treatments nor low-frequency spinal cord stimulation (SCS) has provided significant and long-term pain relief for patients with PDN. This study aims to document the value of 10-kHz SCS in addition to conventional medical management (CMM) compared with CMM alone in patients with refractory PDN.

METHODS

In a prospective, multicenter, randomized controlled trial (SENZA-PDN), 216 subjects with PDN will be assigned 1:1 to receive 10-kHz SCS combined with CMM or CMM alone after appropriate institutional review board approvals and followed for 24 months. Key inclusion criteria include (1) symptoms of PDN for at least 12 months, (2) average pain intensity of at least 5 cm-on a 0- to 10-cm visual analog scale (VAS)-in the lower limbs, and (3) an appropriate candidate for SCS. Key exclusion criteria include (1) large or gangrenous ulcers or (2) average pain intensity of at least 3 cm on VAS in the upper limbs or both. Along with pain VAS, neurological assessments, health-related quality of life, sleep quality, and patient satisfaction will be captured. The primary endpoint comparing responder rates (≥50% pain relief) and safety rates between the treatment groups will be assessed at 3 months. Several secondary endpoints will also be reported on.

DISCUSSION

Enrollment commenced in 2017 and was completed in 2019. This study will help to determine whether 10-kHz SCS improves clinical outcomes and health-related quality of life and is a cost-effective treatment for PDN that is refractory to CMM.

TRIAL REGISTRATION

ClincalTrials.gov identifier: NCT03228420 (registered 24 July 2017).

Supplementation with Korean Red Ginseng Improves Current Perception Threshold in Korean Type 2 Diabetes Patients: A Randomized, Double-Blind, Placebo-Controlled Trial

BACKGROUND

Many Type 2 diabetes (T2DM) patients in Korea take Korean Red Ginseng (KRG) for various reasons. In this study, we investigated the effects of KRG administration on diabetic peripheral neuropathy in T2DM patients.

METHODS

This study was a randomized, double-blind, placebo-controlled trial. Participants were randomly allocated to either the placebo or KRG group and took corresponding tablets for 24 weeks. The primary outcomes were changes in current perception threshold (CPT) at week 24. Secondary outcomes were altered fasting plasma glucose, HbA1c, and various metabolic and inflammatory markers at week 24.

RESULTS

Sixty-one patients completed the study. The CPT of the lower extremities at various frequencies exhibited significant improvements at week 24 in the KRG group. Other metabolic parameters were not altered after 24 weeks in both groups. In the subgroup analysis, CPT levels were improved in those with a longer diabetes duration or who already had neuropathy at the beginning of the study, and insulin resistance was improved in patients with a shorter diabetes duration.

CONCLUSION

Twenty-four week administration of KRG in T2DM patients resulted in a significant improvement in neuropathy, especially in those with a longer diabetes duration. A further, larger population study with a longer follow-up period is warranted to verify the effects of KRG on diabetic neuropathy.

['Point of no return' in diabetic neuropathies: a dangerous delusion]

Polyneuropathy in patients with diabetes mellitus is manifested by a lesion of peripheral sensory, motor and autonomic nervous system. Different severity of damage of sensory, motor and autonomic fibers in typical and atypical forms of diabetic polyneuropathy, requires a differentiated approach to therapy, but not the rejection of its implementation. In an interdisciplinary consensus, consultations are held with physicians from different regions of the Russian Federation, and modern methods of diagnosing and assessing the severity of diabetic polyneuropathies, which determine the algorithm for treating patients, are discussed.

[The efficacy of cocarnit in diabetic neuropathy]

AIM

To study the efficacy of the complex therapy, including cocarnit (group B vitamins, triphosadenine and nicotinamide), of diabetic neuropathy.

MATERIAL AND METHODS

Forty-one patients with diabetes mellitus type 2 and distal symmetric sensorimotor polyneuropathy were examined. Patients were divided into 2 groups. Patients of the main group (n=26) received complex therapy, including cocarnit, and patients of the comparison group (n=15) received standard treatment.

RESULTS AND CONCLUSION

The positive dynamics based on the VAS (р=0.0001), TSS (р=0.0001), NSS (р=0.001), NDS (р=0.0431), SF-36 (р=0.0008), electroneuromyographic results and glycated hemoglobin levels was observed in the main group. In patients of the comparison group, the positive dynamics was instable; the scores of clinical scales did not reach statistical significance. The results suggest the use of cocarnit in the complex treatment of patients with diabetic neuropathy.

[Etiopathogenetic factors of peripheral neuropathic pain in rheumatoid arthritis]

AIM

To determine a neuropathic component of pain and define its causes in patients with rheumatoid arthritis (RA).

MATERIAL AND METHODS

One hundred and eighty-three patients with confirmed RA, mean age 46,5±11,7 years, RA duration from 3 month to 30 years, were studied. Rheumatology, neurological, using the DN4 questionnaire, examinations and stimulation electromyography were used. Results and сonclusion. Signs of neuropathic pain (NP) assessed with the DN4 were identified in 73 (43%) patients with RA. These patients were older, had longer RA duration as well as higher clinical stage of disease and reduced functional abilities. There were no correlation between NP and disease activity. Peripheral nervous system (PNS) lesions were seen in 96% patients with NP: sensory motor neuropathy (55%), tunnel syndrome (14%), mononeuropathy (19%) and their combinations (4%), cervical myelopathy (4%). PNS lesions is the main etiopathogenetic factor of peripheral NP in RA. This finding opens new perspectives for complex treatment, including group B vitamins, of chronic pain in RA.