Are herbal medicines alone or in combination for diabetic peripheral neuropathy more effective than methylcobalamin alone? A systematic review and meta-analysis

Highlights

• Herbal medicines have been used to treat diabetic peripheral neuropathy (DPN).

• Seventy-two randomized controlled trials were included in the present study.

• Herbal medicines revealed a better effect on treating patients with DPN compared to methylcobalamin alone.

• Herbal medicine and CHM were found to be relatively safe without adverse effects.

• Further rigorous studies will have to be conducted.

Abstract

Background and purpose

In Asian countries, herbal medicines have been used to treat diabetic peripheral neuropathy (DPN) as an adjunctive therapy. This review aims to assess the effectiveness and safety of herbal medicines for the treatment of DPN.

Methods

A literature search was conducted on PubMed, Embase, CENTRAL, Scopus, CINAHL, CNKI, DBPIA, and OASIS for randomized controlled trials that evaluated the effects of herbal medicines on DPN. The oral methylcobalamin administered group was selected as the control. The primary outcome measure was nerve conduction velocity (NCV), and the secondary outcome measure was the total efficacy rate (TER). The methodological quality of the included studies was assessed using the Cochrane risk of bias tool. A meta-analysis was conducted using Review Manager 5.4.1 software.

Results

Seventy-two RCTs with a total of 6260 patients were included. The meta-analysis showed that herbal medicine and co-administration of herbal medicine and methylcobalamin (CHM) treatment for DPN significantly increased the sensory nerve conduction velocity (SNCV) and motor nerve conduction velocity (MNCV) of the median and common peroneal nerves than methylcobalamin treatment alone. Herbal medicine and CHM treatment for DPN also significantly improved the TER compared to the control group. Herbal medicine and CHM treatment was found to be relatively safe.

Conclusion

Our study suggests that herbal medicine and CHM might be more effective than methylcobalamin alone in the management of DPN. Further rigorous studies should be conducted to make more definite conclusions.

Introduction

Diabetic peripheral neuropathy (DPN) is one of the most common peripheral neuropathic complications of diabetes [1]. The prevalence of DPN varies according to previous studies. In Korea, it is reported that the prevalence of DPN per year in diabetic patients is 20.5–26.6% [2]. Many patients with DPN experience pain, anxiety, depression, and insomnia. This lowers patients’ quality of life and productivity and causes economic losses for both patients and society [3]. In DPN, gradual damage to the nerve fibers affects sensory and motor functions and leads to clinical features such as symmetrical numbness and pain in the limbs [4]. Although controlling the blood sugar level is essential to prevent and slow the progression of DPN, normalization of the blood sugar level through strict dietary control is difficult for most patients. In addition, controlling blood sugar alone may not be effective for DPN that has already occurred [5]. Different medications are available for pain relief. However, there is a lack of evidence on the most effective medication for DPN, and medications cannot treat underlying nerve damage.

As there is a lack of treatment for DPN, which is a major complication of diabetes, studies are actively being conducted to assess the effectiveness and safety of herbal medicines for the treatment of DPN. Previous randomized controlled studies have shown that herbal medicines improve symptoms, nerve conduction velocity, and pain in DPN [6,7]. Additionally, herbal medicines inhibit apoptosis and induce the proliferation of Schwann cells, reduce oxidative stress, and increase the expression of various neurotrophic factors and genes for nerve regeneration in animal models [8,9].

Systematic reviews of the effectiveness of herbal medicines on DPN have been reported. However, there are methodological limitations, such as poor study quality and a small number of samples [[10], [11], [12], [13]]. As many studies have been published, the current study aims to systematically review the literature and meta-analyze the latest studies to verify the effectiveness and safety of herbal medicine for DPN.