External OTC Vagus Nerve Stimulators: Safety and Efficacy
Direct Answer
External over-the-counter vagus nerve stimulators are not FDA-approved for any medical condition, and there is insufficient evidence to recommend their use for epilepsy, depression, anxiety, or other conditions. 1, 2
FDA-Approved VNS Indications
The FDA has only approved implantable vagus nerve stimulation devices for two specific conditions:
- Refractory epilepsy (approved 1997) as adjunctive therapy after failure of two or more anti-epileptic drugs 2, 3, 4
- Treatment-resistant depression (approved 2005) after failure of multiple antidepressant treatments 2
No external or OTC vagus nerve stimulators have FDA approval for any medical indication. 2, 3
Evidence Quality for Non-Invasive VNS
The 2024 VA/DoD Headache Guidelines explicitly state there is insufficient evidence to recommend for or against noninvasive vagus nerve stimulation for migraine treatment or prevention, despite reviewing the available literature through 2023. 1 This represents the most recent high-quality guideline assessment of non-invasive VNS technology.
For other conditions beyond headache:
- Epilepsy: Non-invasive VNS has not been investigated beyond small pilot studies 5
- Depression: Only small pilot studies exist, with no established efficacy 5
- Anxiety: No substantial clinical trial evidence exists 5
Why External Devices Differ from Implantable VNS
Implantable VNS devices achieve therapeutic effects through:
- Direct electrode placement on the left cervical vagal trunk with helical cuff electrodes connected to an implanted pulse generator 2, 4
- Precise stimulation parameters that activate specific nerve fiber types (B-fibers) at therapeutic thresholds 1
- Consistent nerve activation with approximately 51% of epilepsy patients achieving ≥50% seizure reduction 2, 4
External devices cannot replicate these conditions because:
- They lack direct nerve contact, making selective fiber activation extremely difficult 1
- The vagus nerve's broad innervation creates challenges in targeting therapy-producing fibers without activating non-targeted fibers 2
- Optimal stimulation parameters established for implantable devices (typically 20-30 Hz, specific pulse widths, and amplitudes calibrated to individual nerve responses) cannot be reliably delivered transcutaneously 1, 4
Clinical Recommendation Algorithm
For patients considering VNS therapy:
Determine if FDA-approved indication exists (refractory epilepsy after ≥2 failed anti-epileptic drugs, or treatment-resistant depression after multiple failed antidepressants) 2, 3, 4
If yes: Refer for evaluation for implantable VNS device 2, 4
If no: VNS is not indicated; external/OTC devices lack evidence and FDA approval 1, 2, 3
For experimental conditions (stroke rehabilitation, heart failure, anxiety): These remain investigational even for implantable devices and should not be pursued with OTC products 2, 3, 5
Critical Safety Considerations
While implantable VNS has a well-established safety profile with minor side effects (hoarseness, voice alteration, cough during stimulation, ~3% infection rate), 6, 7 the safety profile of external OTC devices has not been adequately studied in rigorous clinical trials. 8, 5
Common pitfall: Patients may purchase OTC vagus nerve stimulators marketed for wellness or various medical conditions based on preliminary research or marketing claims, but these devices lack the clinical validation and FDA oversight that implantable devices underwent through multicenter randomized controlled trials. 4, 8
Bottom Line for Clinical Practice
Do not recommend external OTC vagus nerve stimulators for any medical condition. 1, 2, 3 For patients with refractory epilepsy or treatment-resistant depression who meet FDA-approved criteria, refer for evaluation for implantable VNS therapy, which has demonstrated efficacy in rigorous clinical trials. 2, 4, 6