Can Acapatch Be Used Over a Tendon?
No, capsaicin patches should not be applied directly over tendons, as there is evidence suggesting that capsaicin-induced substance P depletion may impair tendon healing and reduce tensile strength.
Evidence Against Direct Tendon Application
The primary concern stems from research demonstrating that capsaicin treatment interferes with the healing process in tendon tissue:
- Capsaicin depletes substance P by approximately 60% in neural tissue, and this depletion directly correlates with impaired tendon repair 1
- Rats with higher residual substance P levels after capsaicin treatment developed significantly better tensile strength and stress at failure during Achilles tendon healing 1
- Individual residual substance P levels in dorsal root ganglia correlated with critical biomechanical properties including transverse area (r = 0.39), ultimate tensile strength (r = 0.53), and stress at failure (r = 0.43) 1
Mechanism of Concern
Capsaicin works by depleting substance P from sensory C-fibers, creating a desensitizing effect that is fully reversible 2. However, this same mechanism appears problematic for tendon healing:
- Substance P plays a crucial role in tendon repair, and its depletion compromises the biomechanical integrity of healing tendon tissue 1
- The correlation between pain sensitivity (which reflects substance P presence) and improved tensile strength (r = 0.89) and stress at failure (r = 0.78) suggests substance P is essential for proper tendon healing 1
Approved Indications for Capsaicin Patches
Capsaicin 8% dermal patches are indicated for peripheral neuropathic pain in adults, not for tendinopathy 3. The evidence supports use in:
- Painful diabetic peripheral neuropathy 3
- Postherpetic neuralgia 3
- Non-diabetic peripheral neuropathic pain 3
- Chronic non-specific low back pain (musculoskeletal disorders) 2
Recommended Alternatives for Tendinopathy
For tendon-related pain, evidence-based treatments should be prioritized instead:
- Topical NSAIDs are the preferred topical analgesic for tendon pain, as they effectively reduce pain without the gastrointestinal risks of systemic NSAIDs and do not interfere with tendon healing 4
- Relative rest, cryotherapy (ice through wet towel for 10-minute periods), and eccentric strengthening exercises form the foundation of tendinopathy management 4, 5, 6
- Approximately 80% of patients with overuse tendinopathies recover within 3-6 months using conservative treatment without capsaicin 4, 5, 6
Critical Caveat
Avoid any intervention that may compromise tendon integrity, particularly in patients with active tendinopathy or recent tendon injury, as the risk of impaired healing and reduced tensile strength could predispose to tendon rupture 4, 1.