Can capsaicin ointment be used on the upper and lower extremities for breakthrough neuropathy in a patient already on gabapentin (Neurontin)?

Capsaicin Ointment for Upper and Lower Extremity Neuropathy

Yes, capsaicin can be applied to both upper and lower extremities for breakthrough neuropathic pain in patients already on gabapentin, though the formulation and application protocol matter significantly for efficacy and tolerability.

Formulation Selection

For breakthrough neuropathic pain, you have two distinct options with different evidence profiles:

High-Concentration Capsaicin (8% Patch) - Preferred Option

• The 8% capsaicin patch is FDA-approved and provides sustained pain relief lasting up to 12 weeks from a single 30-60 minute application 1, 2
• This formulation can be applied to any affected area of intact skin on upper or lower extremities under medical supervision 1
• Approximately 31% of patients achieve >30% pain reduction compared to 14% with placebo, with effects beginning around week 2 and lasting through 8-12 weeks 1, 2

Low-Concentration Capsaicin (0.075% Cream)

• The cream formulation requires application 3-4 times daily for 6 weeks to achieve efficacy 1
• This has moderate evidence supporting its use, with a number needed to treat (NNT) of 6.6 for any pain relief over 6-8 weeks 3
• The cream can be applied to upper and lower extremities but requires consistent adherence to the frequent dosing schedule 1

Application Protocol for 8% Patch (Recommended)

Critical pre-treatment steps to ensure tolerability:

• Apply topical lidocaine 4% to the treatment area for 60 minutes before capsaicin patch application - this is the most critical step for tolerability 1, 4
• Consider prescribing short-acting opioids (such as hydrocodone with acetaminophen) or acetaminophen for use during application and up to 7 days post-application for breakthrough burning pain 1
• The patch should remain in place for 30-60 minutes (60 minutes for postherpetic neuralgia, 30 minutes for other neuropathic conditions) 1

Safety Precautions for Extremity Application

Essential warnings to prevent serious adverse events:

• Warn patients to avoid contact with eyes, mucous membranes, and genitalia - capsaicin is a potent local irritant 1
• Patients must wear gloves during application to avoid inadvertent transfer to sensitive areas 1
• Only apply to intact skin; avoid broken or irritated skin 1

Expected Outcomes and Timeline

• Pain relief typically begins around week 2 and continues through 8-12 weeks after a single application 1, 2
• Treatment can be repeated every 90 days if pain persists or returns 1
• Local skin reactions (erythema, burning, application site pain) are common but usually mild and transient 1, 3

Combination with Gabapentin

Capsaicin works through a different mechanism than gabapentin, making it a rational add-on therapy:

• Capsaicin binds to TRPV1 receptors and decreases release of pain neurotransmitters like substance P 1
• This mechanism is complementary to gabapentin's action on calcium channels 5
• Topical treatments like capsaicin are particularly valuable when oral medications provide inadequate relief or when localized pain is present 1

Common Pitfalls to Avoid

• Do not skip lidocaine pretreatment - this is the most common reason for poor tolerability 1
• Do not use low-concentration cream expecting rapid relief - it requires 6 weeks of consistent 3-4 times daily application 1
• Do not apply to large surface areas simultaneously with the 8% patch - treat the most painful areas first 4
• Inadequate pain management during and after application leads to poor patient experience and discontinuation 1