Vitamin B6 in Health Supplements and Neuropathy: Case Series Assessment of Spontaneously Reported Cases

The potential hazards of high doses of vitamin B6 in treating nausea and vomiting in pregnancy: A systematic review

Vitamin B6 is frequently utilized as a therapeutic agent for nausea and vomiting of pregnancy (NVP). Research indicates that excessive intake of vitamin B6 can have implications on neurological function, underscoring the importance of cautious consideration when administering vitamin B6 treatment during early pregnancy. This systematic review investigates the effects of high doses of vitamin B6 on pregnant women experiencing NVP. We searched the PubMed® MEDLINE® database for articles using the following terms: "pregnancy" or "nausea and vomiting during pregnancy" and "vitamin B6." Women with nausea and vomiting symptoms during pregnancy use more than the tolerable amount of vitamin B6. A total of 136 articles were identified from the PubMed® MEDLINE® database. The etiology and treatment of NVP are briefly outlined, followed by a summary and analysis of 19 relevant literature sources. Among these sources, 12 reports detailed the adverse effects of excessive vitamin B6 intake in women; 164/1226 individuals experienced neurological symptoms such as burning, tingling, paresthesia, ataxia, or perioral numbness. Additionally, out of 245 women, four experienced miscarriages and one had an intrauterine demise. The overconsumption of vitamin B6 has the potential to impact nerve function, particularly during the critical first trimester of embryonic development. It might result in adverse outcomes such as miscarriage, intrauterine fetal demise, and congenital abnormalities.

The association between the knowledge, perception, and practice of dietary supplement among Chinese adults

Introduction

Rapid growth has been found in the market of dietary supplements (DSs) in China. However, studies about the knowledge level, intentions, and behavior related to DS remained limited in the Chinese population. This study aimed to explore the knowledge level, perception, and practice toward DS among Chinese adults.

Methods

This is a cross-sectional design among 1,714 participants aged between 18 and 65 years. A total of 54.1% of participants reported purchasing supplements in the past 6 months. Knowledge levels were assessed with a score from 1 to 10 based on correct answers to 10 binary questions about supplements.

Results

Only 29.1% of participants answered seven or more questions correctly, while 7.9% answered three or fewer questions correctly. Participants with high and middle knowledge levels were more likely to seek medical advice when experiencing discomfort symptoms and were less likely to choose DS, with corresponding odd ratios (ORs) of 1.58 (95% CI: 1.16, 2.13) and 0.69 (95% CI: 0.52, 0.91) in high knowledge group and ORs of 1.36 (95% CI: 1.03, 1.80) and 0.96 (95% CI: 0.72, 1.30) in middle knowledge group (P for trend = 0.003 and 0.028, respectively). No significant differences were found in the motivation of DS use between knowledge levels. Although higher knowledge levels were associated with less spending on DS (OR high = 0.69; 95% CI: 0.49, 0.99; OR middle = 0.88; 95% CI: 0.64, 1.20; P for trend = 0.038), it did not guarantee better and more accurate awareness toward DS use.

Discussion

In conclusion, there is a growing demand for supplements among Chinese adults, but a significant gap between knowledge and behavior exists, affecting decision-making behaviors regarding DS.

Vitamin B6 Toxicity Secondary to Daily Multivitamin Use: A Case Report

Vitamin B6 is a water-soluble vitamin that is an important cofactor in various metabolic processes. Although rare, its consumption can sometimes result in toxicity, which typically presents with peripheral neuropathy in the early stage. While vitamin B6 toxicity is most often associated with supplemental mega-doses of more than 50 mg/day, more recent studies have shown that toxicity can occur in cases of much smaller doses as well. We present a case of a 73-year-old male with a three-year history of progressive peripheral neuropathy who was found to have a serum vitamin B6 level of 259.9 nmol/L (reference range: 20-125 nmol/L) but only reported taking a daily multivitamin containing 6 mg of vitamin B6. This case of toxicity in the setting of a daily intake lower than the European Food Safety Administration's (EFSA) newly established Tolerable Upper Intake Level (UL) of 12 mg/day highlights the need for further research into the effects of relatively low-dose vitamin B6 supplementation.

The Role of Vitamin B6 in Peripheral Neuropathy: A Systematic Review

INTRODUCTION

Vitamin B6 is a water-soluble vitamin that is naturally present in many foods and is accessible in many dietary supplements. The three natural forms are pyridoxine, pyridoxal, and pyridoxamine. Both vitamin B6 deficiency and high B6 intake have been described as risk factors for developing peripheral neuropathy (PN). The aim of this systematic review is to characterize and comprehensively describe B6-related PN.

METHOD

A systematic, computer-based search was conducted using the PubMed database. Twenty articles were included in this review.

RESULTS

Higher vitamin B6 levels, which usually occur following the taking of nutritional supplements, may lead to the development of a predominantly, if not exclusively, sensory neuropathy of the axonal type. After pyridoxine discontinuation, such patients subjectively report improved symptoms. However, although low vitamin B6 levels can be seen in patients suffering from peripheral neuropathy of various etiologies, there is no firm evidence that low B6 levels have a direct causal relationship with PN. Many studies suggest subjective improvement of neuropathy symptoms in patients suffering from PN of various etiologies after receiving B6 supplementation; however, no data about B6 administration as a monotherapy exist, only as part of a combination treatment, usually with other vitamins. Therefore, the potential therapeutic role of B6 cannot be confirmed to date. Supplementation with vitamin B6, even as part of a nutritional multivitamin supplement, has not been proven harmful at permitted daily doses in patients who already suffer from PN.

CONCLUSION

Current scientific evidence supports a neurotoxic role of B6 at high levels. Although some studies suggest that low B6 is also a potential risk factor, further studies in this area are needed.

Scientific opinion on the tolerable upper intake level for vitamin B6

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver a scientific opinion on the tolerable upper intake level (UL) for vitamin B6. Systematic reviews of the literature were conducted by a contractor. The relationship between excess vitamin B6 intakes and the development of peripheral neuropathy is well established and is the critical effect on which the UL is based. A lowest-observed-effect-level (LOAEL) could not be established based on human data. A reference point (RP) of 50 mg/day is identified by the Panel from a case-control study, supported by data from case reports and vigilance data. An uncertainty factor (UF) of 4 is applied to the RP to account for the inverse relationship between dose and time to onset of symptoms and the limited data available. The latter covers uncertainties as to the level of intake that would represent a LOAEL. This leads to a UL of 12.5 mg/day. From a subchronic study in Beagle dogs, a LOAEL of 50 mg/kg body weight (bw) per day can be identified. Using an UF of 300, and a default bw of 70 kg, a UL of 11.7 mg/day can be calculated. From the midpoint of the range of these two ULs and rounding down, a UL of 12 mg/day is established by the Panel for vitamin B6 for adults (including pregnant and lactating women). ULs for infants and children are derived from the UL for adults using allometric scaling: 2.2-2.5 mg/day (4-11 months), 3.2-4.5 mg/day (1-6 years), 6.1-10.7 mg/day (7-17 years). Based on available intake data, EU populations are unlikely to exceed ULs, except for regular users of food supplements containing high doses of vitamin B6.

Electrochemical preparation and the characterizations of poly(3,5-diamino 1,2,4-triazole) film for the selective determination of pyridoxine in pharmaceutical formulations

This work describes the synthesis and characterization of a polymeric film of 3,5-diamino 1,2,4-triazole on a pencil graphite electrode for the selective sensing of pyridoxine (PY). The PGE was modified using the electropolymerization process by the potentiodynamic method. The polymerized electrode (PDAT/PGE) was characterized by IR, SEM, AFM, cyclic voltammetry, and electrochemical impedance spectroscopy. PY undergoes irreversible oxidation at 0.79 V on PDAT/PGE in phosphate buffer of pH 5. Using the differential pulse voltammetric technique (DPV), PY showed a linear range from 5 to 950 μM with a lower detection limit of 2.96 μM. The PDAT/PGE was applied for the analytical determination of PY in pharmaceutical tablets with good recovery.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11696-023-02777-5.

Pneumocystis jirovecii pneumonia associated with immune checkpoint inhibitors: A systematic literature review of published case reports and disproportionality analysis based on the FAERS database

Background: Pneumocystis jirovecii pneumonia (PJP) has been reported with ICIs but limited to case reports. The clinical features of PJP with ICIs remain mostly unknown. This study aims to investigate the association of PJP with ICIs and describe clinical features.

Methods: Reports of PJP recorded in FAERS (January 2004–December 2022) were identified through the preferred term “Pneumocystis jirovecii pneumonia”. Demographic and clinical features were described, and disproportionality signals were assessed through the Reporting Odds Ratio (ROR) and Information Component (IC), using traditional chemotherapy and targeted therapy as comparators, and adjusting signals by excluding contaminant immunosuppressive drugs and pre-existing diseases. A systematic literature review was conducted to describe clinical features of published PJP reports with ICIs. Bradford Hill criteria was adopted for global assessment of the evidence.

Results: We identified 677 reports of PJP associated with ICIs, in which 300 (44.3%) PJP cases with fatal outcome. Nivolumab (IC025 2.05), pembrolizumab (IC025 1.88), ipilimumab (IC025 1.43), atezolizumab (IC025 0.36), durvalumab (IC025 1.65), nivolumab plus ipilimumab (IC025 1.59) have significant signals compared to other drugs in FAERS database. After excluding pre-existing diseases and immunosuppressive agents which may increase susceptibility of PJP, the signals for PJP associated with nivolumab, pembrolizumab, durvalumab, nivolumab plus ipilimumab remained robust (IC025 > 0). When compared to other anticancer regimens, although all ICIs showed a lower disproportionate signal for PJP than chemotherapy, nivolumab (IC025 0.33, p < 0.001), pembrolizumab (IC025 0.16, p < 0.001), both PD-1 inhibitors, presented a higher signal for PJP than targeted therapy. Male gender (IC025 0.26, p < 0.001) and age >65 years (IC025 0.38, p < 0.001) were predominant in PJP cases associated with across all ICIs. In literature, 15 PJP cases associated with ICIs were reported in 10 published case reports. 12 of 15 (80.0%) of cases received PD-1 inhibitors before PJP was diagnosed.

Conclusion: By the combined analysis of post-marketing data from FAERS and published case reports, we identified ICIs may be associated with PJP, especially in males aged >65years. After accounting for confounders, PD-1 inhibitors emerged with a robust disproportionality signal when compared to PD-L1/CTLA-4 inhibitors as well as targeted therapy. Further research is warranted to validate our findings.

Hypophosphatasia: Vitamin B6 status of affected children and adults

Hypophosphatasia (HPP) is the heritable dento-osseous disease caused by loss-of-function mutation(s) of the gene ALPL that encodes the tissue-nonspecific isoenzyme of alkaline phosphatase (TNSALP). TNSALP is a cell-surface homodimeric phosphomonoester phosphohydrolase expressed in healthy people especially in the skeleton, liver, kidneys, and developing teeth. In HPP, diminished TNSALP activity leads to extracellular accumulation of its natural substrates including inorganic pyrophosphate (PPi), an inhibitor of mineralization, and pyridoxal 5'-phosphate (PLP), the principal circulating form of vitamin B₆ (B₆). Autosomal dominant and autosomal recessive inheritance involving >450 usually missense defects scattered throughout ALPL largely explains the remarkably broad-ranging severity of this inborn-error-of-metabolism. In 1985 when we identified elevated plasma PLP as a biochemical hallmark of HPP, all 14 investigated affected children and adults had markedly increased PLP levels. However, pyridoxal (PL), the dephosphorylated form of PLP that enters cells to cofactor many enzymatic reactions, was not low but often inexplicably elevated. Levels of pyridoxic acid (PA), the B₆ degradation product quantified to assess B₆ sufficiency, were unremarkable. Canonical signs or symptoms of B₆ deficiency or toxicity were absent. B₆-dependent seizures in infants with life-threatening HPP were later explained by their profound deficiency of TNSALP activity blocking PLP dephosphorylation to PL and diminishing gamma-aminobutyric acid synthesis in the brain. Now, there is speculation that altered B₆ metabolism causes further clinical complications in HPP. Herein, we assessed the plasma PL and PA levels accompanying previously reported elevated plasma PLP concentrations in 150 children and adolescents with HPP. Their mean (SD) plasma PL level was nearly double the mean for our healthy pediatric controls: 66.7 (59.0) nM versus 37.1 (22.2) nM (P < 0.0001), respectively. Their PA levels were broader than our pediatric control range, but their mean value was normal; 40.2 (25.1) nM versus 39.3 (9.9) nM (P = 0.7793), respectively. In contrast, adults with HPP often had plasma PL and PA levels suggestive of dietary B₆ insufficiency. We discuss why the B₆ levels of our pediatric patients with HPP would not cause B₆ toxicity or deficiency, whereas in affected adults dietary B₆ insufficiency can develop.

Nutraceuticals as Potential Targets for the Development of a Functional Beverage for Improving Sleep Quality

Functional beverages can be a valuable component of the human diet with the ability to not only provide essential hydration but to deliver important bioactive compounds that can contribute to chronic disease treatment and prevention. One area of the functional beverage market that has seen an increase in demand in recent years are beverages that promote relaxation and sleep. Sleep is an essential biological process, with optimal sleep being defined as one of adequate duration, quality and timing. It is regulated by a number of neurotransmitters which are, in turn, regulated by dietary intake of essential bioactive compounds. This narrative review aimed to evaluate the latest evidence of the sleep promoting properties of a selection of bioactive compounds (such as L-theanine and L-tryptophan) for the development of a functional beverage to improve sleep quality; and the effectiveness of traditional sleep promoting beverages (such as milk and chamomile). Overall, the bioactive compounds identified in this review, play essential roles in the synthesis and regulation of important neurotransmitters involved in the sleep-wake cycle. There is also significant potential for their inclusion in a number of functional beverages as the main ingredient on their own or in combination. Future studies should consider dosage; interactions with the beverage matrix, medications and other nutraceuticals; bioavailability during storage and following ingestion; as well as the sensory profile of the developed beverages, among others, when determining their effectiveness in a functional beverage to improve sleep quality.

Vitamin B-6-Induced Neuropathy: Exploring the Mechanisms of Pyridoxine Toxicity

Vitamin B-6 in the form of pyridoxine (PN) is commonly used by the general population. The use of PN-containing supplements has gained lots of attention over the past years as they have been related to the development of peripheral neuropathy. In light of this, the number of reported cases of adverse health effects due to the use of vitamin B-6 have increased. Despite a long history of study, the pathogenic mechanisms associated with PN toxicity remain elusive. Therefore, the present review is focused on investigating the mechanistic link between PN supplementation and sensory peripheral neuropathy. Excessive PN intake induces neuropathy through the preferential injury of sensory neurons. Recent reports on hereditary neuropathy due to pyridoxal kinase (PDXK) mutations may provide some insight into the mechanism, as genetic deficiencies in PDXK lead to the development of axonal sensory neuropathy. High circulating concentrations of PN may lead to a similar condition via the inhibition of PDXK. The mechanism behind PDXK-induced neuropathy is unknown; however, there is reason to believe that it may be related to γ-aminobutyric acid (GABA) neurotransmission. Compounds that inhibit PDXK lead to convulsions and reductions in GABA biosynthesis. The absence of central nervous system-related symptoms in PDXK deficiency could be due to differences in the regulation of PDXK, where PDXK activity is preserved in the brain but not in peripheral tissues. As PN is relatively impermeable to the blood-brain barrier, PDXK inhibition would similarly be confined to the peripheries and, as a result, GABA signaling may be perturbed within peripheral tissues, such as sensory neurons. Perturbed GABA signaling within sensory neurons may lead to excitotoxicity, neurodegeneration, and ultimately, the development of peripheral neuropathy. For several reasons, we conclude that PDXK inhibition and consequently disrupted GABA neurotransmission is the most plausible mechanism of toxicity.

Neuropsychiatric toxicity and cycloserine concentrations during treatment for multidrug-resistant tuberculosis

BACKGROUND

Cycloserine, or its structural analogue terizidone, has been associated with neuropsychiatric toxicity (psychosis, depression, and neuropathy). Prospective clinical data on the incidence of and risk factors for neuropsychiatric toxicity in TB patients treated with cycloserine are limited.

METHODS

A prospective evaluation of neuropsychiatric toxicity was performed using validated screening tools in patients with multidrug-resistant tuberculosis treated with terizidone. Cox proportional hazard modelling was performed to explore the effects of clinical variables and measures of cycloserine pharmacokinetics in plasma.

RESULTS

A total 144 participants were recruited: 86 were male and 58 were female; their median age was 35.7 years and 91 (63%) were HIV-infected. Fifty-five (38%) participants developed at least one neuropsychiatric event (30 cases per 100 person-months): 50 (35%) neuropathy, 14 (10%) depression, and 11 (8%) psychosis. Neuropathy was independently associated with cycloserine clearance ((adjusted hazard ratio 0.34 (aHR), P = 0.03)) and high-dose pyridoxine (200 mg vs 150 mg daily, aHR: 2.79, P = 0.01).

CONCLUSIONS

A high incidence of early neuropsychiatric toxicity was observed in this cohort of patients treated with terizidone. Cycloserine clearance and higher doses of pyridoxine are associated with incident or worsening peripheral neuropathy.

[B vitamins in geriatrics - what to determine, what to replace?]

Deficiencies in B-vitamins have recently been recognized as risk factors for stroke and dementia. With increasing age there is an increased prevalence of metabolic and nutritional changes leading to increased vulnerability of vitamin deficiency. Especially in geriatric patients, these changes can have effects on the nervous system that are often not recognized. Often, however, vitamins in particular are taken uncritically and attributed with a variety of unspecific properties.With regard to the knowledge about the water-soluble B vitamins (B₆, B₁₂, folic acid and homocysteine as well as B₁), there have recently been new findings and recommendations by various professional societies. An overview of the basics, causes, diagnostic and therapeutic concepts of B-vitamins and the current state of research in this area is given.

Update on Safety Profiles of Vitamins B1, B6, and B12: A Narrative Review

The neurotropic B vitamins B1 (thiamine), B6 (pyridoxine), and B12 (cobalamin) are essential for proper functioning of the nervous system. Deficiencies may induce neurological disorders like peripheral neuropathy (PN) and mainly occur in vulnerable populations (eg, elderly, diabetics, alcoholics). As epidemiologic cohort studies raised safety concerns about vitamin B6/B12 intake being potentially associated with increased risks of hip fracture (HF) and lung cancer (LC), we explored these aspects and performed comprehensive literature searches. However, we suggest not to neglect actual high-risk factors (eg, smoking in LC, higher age in HF) by focusing on individual nutrients, but to examine the complex interaction of numerous factors involved in disease development. Because it warrants continued consideration, we also provide an update on neurotoxicity associated with vitamin B6. We consider that neurological side effects due to vitamin B6 intake are rare and only occur with high daily doses and/or longer treatment duration. The benefit-risk ratio of high-dose treatment with neurotropic B vitamins in indications like PN is therefore considered advantageous, particularly if dosing recommendations are followed and serum levels monitored.

The use of animal models to study cell transplantation in neuropathic hearing loss

Auditory neuropathy (AN) is a form of sensorineural deafness specifically affecting the conduction of the nerve impulse from the cochlear hair cells to the auditory centres of the brain. As such, the condition is a potential clinical target for 'cell replacement therapy', in which a functioning auditory nerve is regenerated by transplanting an appropriated neural progenitor. In this review, we survey the current literature and examine possible experimental models for this condition, with particular reference to their compatibility as suitable hosts for transplantation. The use of exogenous neurotoxic agents such as ouabain or β-bungarotoxin is discussed, as are ageing and noise-induced synaptopathy models. Lesioning of the nerve by mechanical damage during surgery and the neuropathy resulting from infectious diseases may be very relevant clinically, and we discuss whether there are good models for these situations. We also address genetic models for AN, examining whether the phenotypes truly model the clinical situation in their human counterpart syndromes - we use the example of the hyperbilirubinaemic Gunn rat as a particular instance in this regard.

Fifteen years of patient reporting -what have we learned and where are we heading to?

INTRODUCTION

In April 2003, the Netherlands Pharmacovigilance Centre Lareb successfully implemented patient reporting to their spontaneous reporting system. The number of reports by patients rapidly grew, prompting the need to evaluate the value of the patient reporting scheme and to compare experiences with other countries. The aim of this article is to summarize our 15-year experience of working with direct patient reporting in pharmacovigilance and to discuss necessary steps in order to optimize the use of patient reports in the future.

AREAS COVERED

This article is based on Lareb studies on patient reporting from 2004 onwards and covers the evolution of the Dutch patient reporting system, the value of patient participation in pharmacovigilance, the impact of patient reporting on the spontaneous reporting system and future steps to strengthen patient reporting.

EXPERT OPINION

After 15 years of experience with patient reporting we conclude that patients can add value to pharmacovigilance. We recognize that there is a big leap between allowing patients to report and actual patient involvement in pharmacovigilance. It is our belief that increased patient involvement in pharmacovigilance is a way to improve pharmacovigilance, enhancing the general public's trust in medicines.

Regressive pyridoxine-induced sensory neuronopathy in a patient with homocystinuria

Pyridoxine (vitamin B6) is an essential vitamin playing a crucial role in amino acid metabolism. Pyridoxine is used for isoniazid side-effects prevention, pyridoxine-dependent epilepsy treatment and cystathionine beta-synthase deficiency (homocystinuria) treatment. However, vitamin B6 hypervitaminosis is neurotoxic and may provoke a progressive sensory neuronopathy (sensory ganglionopathy), usually when daily uptake is above 50 mg. We describe the case of a 30-year-old patient with homocystinuria who was treated with pyridoxine 1250-1750 mg/day for 20 years and developed progressive sensory neuropathy with ataxia and impaired sensation in the extremities. Electrodiagnostic testing demonstrated non-length-dependent abnormalities of sensory nerve potentials, and sensory ganglionopathy was diagnosed. Pyridoxine dosage was reduced to 500 mg/day, resulting in the disappearance of sensory symptoms and ataxia, and the normalisation of sensory nerve potentials. Our case indicates that pyridoxine-induced sensory ganglionopathy may be reversible, even after prolonged ingestion of high doses of vitamin B6 for more than 20 years.