Open Source Apothecary At Home / Muscles, joints and nerves

Nerve pain: capsaicin, alpha-lipoic acid, and what has real evidence

Capsaicin has regulatory approval and trial evidence. Most of what is sold for nerve pain does not.

remedy

Neuropathic pain — the burning, shooting, electric quality of diabetic neuropathy, post-herpetic neuralgia, and nerve injury — responds poorly to ordinary painkillers and is genuinely difficult to treat. The options with evidence are prescription drugs (gabapentinoids, tricyclics, duloxetine), and two topical or nutritional approaches.

Capsaicin, topically, is the best-supported plant intervention here. It works by depleting substance P and desensitising TRPV1-expressing nociceptors, and high-concentration patches have regulatory approval for post-herpetic neuralgia and painful diabetic peripheral neuropathy. It hurts when applied — that is the mechanism — and the first week of low-concentration cream is uncomfortable. Do not apply it to the face, near the eyes, or to broken skin, and wash hands thoroughly afterwards.

Alpha-lipoic acid has trials in diabetic peripheral neuropathy showing improvement in symptoms, with the evidence being moderate at best and the trials mostly small and short. It is well tolerated. It is the most reasonable oral adjunct on this page.

What has weak or absent evidence. Many products sold for "nerve support" — B-vitamin combinations beyond correcting a deficiency, various herbal blends, and most of what is marketed for neuropathy. Where a person has a deficiency, correcting it is the intervention; beyond that, the evidence is thin.

The thing that actually changes the disease in diabetic neuropathy. Glycaemic control and, where present, alcohol reduction and B12 status. Stopping the progression is the treatment, and it is unglamorous. A person with diabetes and burning feet needs their glucose control, their B12 checked (metformin lowers it), their alcohol intake reviewed, and their feet examined — not a supplement.

Topical NSAIDs are for musculoskeletal pain, not neuropathy, and are mentioned here only because people apply them to burning feet. They will not help.

What the studies found

Preparation

Capsaicin cream (low concentration)

• Start with 0.025-0.075%, a small amount, no more than 3-4 times daily
• It burns. That is expected. Apply with gloves or wash hands immediately and thoroughly.
• Do not use near the eyes, on the face, on broken skin, or on a large area at once
• Give it 2-4 weeks; the stinging reduces with repeated use

Capsaicin patch (high concentration)

• 8% patch applied in a clinic, for post-herpetic neuralgia or diabetic neuropathy
• This is a procedure, not a home treatment

Alpha-lipoic acid

• 600 mg daily in the trials, usually by mouth
• Well tolerated; can lower blood sugar slightly, so monitor if on insulin or a sulfonylurea

What to correct before supplementing

• Vitamin B12, which metformin lowers. A deficiency causes neuropathy and it is the treatable cause.
• Blood glucose control in diabetes
• Alcohol intake
• Thyroid function
• These are blood tests and they are the highest-value actions on the page.

Feet, specifically

• Examine daily for wounds, especially with reduced sensation
• Proper footwear; nothing tight
• Any ulcer means medical care, not a cream

Cautions and interactions

• Capsaicin burns. Do not get it in the eyes or on mucous membranes.
• Do not use capsaicin on broken skin or a foot ulcer.
• High-dose B6 can itself cause neuropathy. Do not take large B-vitamin doses for nerve pain without checking the content.
• Alpha-lipoic acid can lower blood glucose. Monitor if on glucose-lowering drugs.
• Metformin lowers B12 — get it checked rather than supplementing blindly.

When this is not a self-care problem — get help

• A new foot ulcer, a black area, spreading redness, or fever in a person with diabetes — urgent assessment. Diabetic foot infections are limb-threatening.
• Rapidly progressive weakness, a foot drop, or loss of bladder control — urgent neurological assessment.

Known interactions

• Alpha-lipoic acid may add to the effect of insulin and sulfonylureas.

Related

• Type 2 diabetes: the herbs with glycaemic trials, and the one that is nearly a drug
• Muscle cramps, and the remedy that failed
• Herb-drug interactions: the ones with numbers behind them
• Exercise and load: the intervention with the best evidence in this section

Sources

1. Disease-modifying therapies for diabetic peripheral neuropathy: A systematic review and meta-analysis of randomized controlled trials. Journal of diabetes and its complications 2024; doi:10.1016/j.jdiacomp.2024.108691 PubMed 38330524
2. Comparative efficacy and safety of Chinese patent medicines as an adjunctive therapy for diabetic peripheral neuropathy: systematic review and network meta-analysis of randomized controlled trials. Pharmaceutical biology 2024; doi:10.1016/j.jep.2024.118355 PubMed 39497372
3. Effects of Oral Alpha-Lipoic Acid Treatment on Diabetic Polyneuropathy: A Meta-Analysis and Systematic Review. Nutrients 2023; doi:10.1212/WNL.0000000000013038 PubMed 37630823
4. Relative safety and efficacy of topical and oral NSAIDs in the treatment of osteoarthritis: A systematic review and meta-analysis. Medicine 2022; doi:10.1097/MD.0000000000030354 PubMed 36086745
5. Effectiveness and safety of non-steroidal anti-inflammatory drugs and opioid treatment for knee and hip osteoarthritis: network meta-analysis. BMJ (Clinical research ed.) 2021; doi:10.1186/1471-2296-13-23 PubMed 34642179