StatPearls [Internet].
Persevering with Training Exercise
This exercise describes the toxicity related to vitamin B6 at larger doses. It explains intimately the pathophysiology and toxicokinetics of vitamin B6 toxicity and affected person signs. This exercise opinions the analysis and remedy of vitamin B6 toxicity and highlights the function of the interprofessional crew in evaluating and treating sufferers with this situation.
Aims:Establish the etiology and epidemiology of vitamin B6 toxicity medical circumstances and emergencies.Define an acceptable historical past, bodily, and analysis for suspected vitamin B6 toxicity.Evaluate an inexpensive differential prognosis for sufferers presenting with indicators and signs of pyridoxine toxicity. Choose the remedy and administration choices accessible to the healthcare crew for vitamin B6 toxicity.Earn persevering with schooling credit (CME/CE) on this subject.
Introduction
Vitamin B6 is a micronutrient required by the physique. Vitamin B6 refers to a number of chemically related compounds of which pyridoxine is the most typical and is the compound present in commercially accessible vitamin dietary supplements. The physique makes use of vitamin B6 in quite a few enzymatic reactions, together with neurotransmitter manufacturing, amino acid metabolism, glucose metabolism, lipid metabolism, hemoglobin synthesis and performance, and gene expression.[1] In the USA, vitamin B6 consumption from meals averages about 1.9 mg/day.[2] Consumption of food-based sources of pyridoxine won’t trigger toxicity. The one reported circumstances of vitamin B6 toxicity are from supratherapeutic dosing of dietary supplements or iatrogenic.
Etiology – “b vitamin toxicity symptoms”
All circumstances of vitamin B6 toxicity are from supratherapeutic dosing, both iatrogenic or laypersons self-treating with over-the-counter dietary supplements. Each day dietary consumption won’t present sufficient pyridoxine to trigger toxicity. Each day dietary consumption of vitamin B6 is roughly 1.9 mg/day in the USA.[2] Moreover, typical pyridoxine doses used for co-treatment with isoniazid is 10 to 25 mg/day. Pyridoxine toxicity sometimes manifests as neurologic signs, together with paresthesias within the extremities and, in extreme circumstances, problem with ambulation. This sensory neuropathy often develops at doses of pyridoxine above 1000 mg per day. There are some case reviews of sensory neuropathies at doses of lower than 500 mg per day in sufferers taking dietary supplements for months. Nevertheless, not one of the research had sensory nerve injury at every day consumption beneath 200 mg pyridoxine per day.[3]
Epidemiology
Vitamin B6 supplementation is a therapeutic possibility for quite a lot of medical circumstances. Pyridoxine is utilized in supratherapeutic doses as an antidote to deal with seizures from isoniazid toxicity.[4] It’s utilized in therapeutic doses for hyperemesis gravidarum and isoniazid.[5][6] It’s used as a dietary complement by the lay public for quite a lot of perceived well being advantages, together with morning illness, heart problems, premenstrual syndrome, despair, and carpal tunnel syndrome. Proof for efficacy for a lot of of those makes use of are blended.
Over-the-counter dietary supplements are the probably offender for sufferers taking in a pyridoxine stage above the protected really helpful higher restrict. Usually sufferers are unaware that top dose pyridoxine might be dangerous. One illustrative case report describes a affected person presenting to a healthcare facility with peripheral neuropathy, and he reported taking vitamin B-complex dietary supplements at fifty instances the every day instructed allowance for ten years.[7]
In response to the 2017 U.S. poison heart knowledge, there have been 566 reviews of utilizing pyridoxine therapeutically as an antidote.[8] Moreover, there have been 377 pyridoxine publicity circumstances reported, together with eight circumstances with solely minor or average medical results. There have been no critical outcomes or deaths reported.
Pathophysiology
Paradoxically the most typical signs related to vitamin B6 toxicity are just like these with vitamin B6 deficiency. A affected person will expertise peripheral sensory neuropathy. Mostly, this causes numbness in a stocking-glove distribution over the extremities. Along with peripheral neuropathy, sufferers can expertise ataxia and disequilibrium as effectively.[9] One giant research discovered that sufferers additionally may expertise hyperesthesia, bone pains, muscle weak point, numbness, and fasciculations.[10]
One research examined the function of pyridoxine toxicity on human cells to look at the neurotoxic results additional. They discovered that pyridoxine induced cell demise in a concentration-dependent trend and inhibited pyridoxal-5-phosphate dependent enzymes.[11] Thus it seems that the inactive type of B6, pyridoxine, competitively inhibits the lively vitamin B6 type, pyridoxal-5’-phosphate inflicting the signs of vitamin B6 toxicity to imitate the signs of vitamin B6 deficiency.