Understanding Capsaicin and How It Works
Capsaicin is the active compound in chili peppers that creates a sensation of heat [1.3.5]. When applied to the skin, it works as a topical analgesic. Its primary mechanism of action involves interacting with a specific receptor on nerve cells called the Transient Receptor Potential Vanilloid 1 (TRPV1) [1.5.4]. Initially, capsaicin activates these receptors, causing the familiar burning or stinging sensation. With prolonged or high-concentration exposure, this activation leads to a "defunctionalization" of the nerve fibers. This process makes the nerve endings less sensitive to pain signals, resulting in an extended period of pain relief [1.5.1]. This is a more complex process than the previously believed theory of simply depleting a chemical called Substance P [1.5.1].
Prescription vs. Over-the-Counter (OTC) Capsaicin
There is a significant difference between the capsaicin products you can buy at a pharmacy and what a doctor can prescribe.
- OTC Capsaicin: These products are typically available as creams, gels, lotions, and low-dose patches. They contain a low concentration of capsaicin, usually ranging from 0.025% to 0.1% [1.2.4]. They are intended for minor aches and pains associated with conditions like arthritis, muscle strains, and sprains [1.4.2].
- Prescription Capsaicin: The only FDA-approved prescription-strength formulation is a high-concentration 8% capsaicin patch sold under the brand name Qutenza [1.2.4, 1.2.7]. It contains approximately 80 times more capsaicin than typical high-potency OTC products [1.3.7]. Due to its high strength, it is not available as a take-home cream and must be administered by a healthcare professional in a clinical setting [1.3.2].
Conditions Treated by Prescription-Strength Capsaicin
The Qutenza (capsaicin 8%) patch is specifically approved by the FDA for treating certain types of neuropathic pain (pain caused by nerve damage) [1.4.4].
- Postherpetic Neuralgia (PHN): This is persistent, often severe nerve pain that can occur after a shingles infection [1.3.5].
- Diabetic Peripheral Neuropathy (DPN): This is nerve damage in the feet caused by diabetes, leading to pain, numbness, or tingling [1.3.3, 1.3.5].
In some cases, it may also be used for other types of neuropathic pain, such as post-surgical nerve pain [1.4.5]. OTC capsaicin is not recommended for treating pain caused by damaged nerves [1.2.1].
Comparison: OTC vs. Prescription Capsaicin
| Feature | Over-the-Counter (OTC) Capsaicin | Prescription Capsaicin (Qutenza) |
|---|---|---|
| Form | Creams, lotions, gels, low-dose patches [1.4.2] | High-concentration 8% patch [1.2.4] |
| Concentration | 0.025% to 0.1% [1.2.4] | 8% (179 mg of capsaicin per patch) [1.3.1, 1.3.7] |
| Application | Self-applied at home, often 3-4 times daily [1.4.2] | Applied by a healthcare professional in-office [1.3.2] |
| Treatment Frequency | Daily application required [1.4.2] | Single 30-60 minute application every 3 months as needed [1.3.1] |
| Primary Use | Minor muscle/joint pain, arthritis [1.2.1, 1.4.2] | Neuropathic pain (PHN, DPN) [1.3.2, 1.4.1] |
| Cost | Relatively low, e.g., $10-$20 per tube [1.7.3, 1.4.5] | High, often several hundred dollars plus clinician fees per treatment [1.4.5, 1.7.3] |
The Qutenza Application Process
Receiving a Qutenza treatment is a medically supervised procedure designed to maximize safety and efficacy [1.8.3].
- Preparation: The healthcare provider identifies and marks the painful area. To reduce the intense burning sensation from the patch, a topical anesthetic may be applied to the site for about an hour beforehand [1.8.1, 1.8.6].
- Application: The Qutenza patch (or up to four patches) is cut to size and applied to the clean, dry, treatment area. It is left in place for 30 minutes for diabetic foot pain or 60 minutes for postherpetic neuralgia [1.3.2]. Healthcare providers wear nitrile gloves and often protective glasses and masks, as aerosolized capsaicin can be an irritant [1.3.6, 1.8.3].
- Monitoring: During the application, the patient is monitored. It is common to experience pain and burning, and the patient's blood pressure may be checked as the pain can cause a temporary increase [1.6.2, 1.8.2].
- Removal and Cleansing: After the allotted time, the patch is gently and slowly removed. A special cleansing gel is applied to the area to remove any residual capsaicin from the skin, and the area is then washed [1.3.1, 1.8.1]. Pain relief can begin within a week or two and may last for up to three months [1.3.7].
Potential Side Effects and Risks
The most common side effects are related to the application site and are generally temporary.
- Application Site Reactions: Significant pain, burning, and redness are very common during and immediately after the procedure [1.6.3]. Swelling, itching, and dryness can also occur [1.6.4].
- Increased Blood Pressure: A temporary increase in blood pressure can happen due to the pain of the application. This is monitored during the procedure [1.6.6].
- Sensory Changes: Some patients may experience a temporary reduction in sensation (like sensing heat) in the treated area, which is usually minor and resolves on its own [1.6.3].
- Respiratory Irritation: Inhalation of capsaicin particles can cause coughing or sneezing, which is why the procedure is done in a well-ventilated area [1.6.2, 1.8.3].
Conclusion
While there is no prescription-strength capsaicin cream, a highly potent prescription option exists in the form of the Qutenza 8% patch. This treatment is a targeted therapy for specific, difficult-to-treat neuropathic pain conditions like PHN and DPN. Unlike daily OTC creams for muscle aches, Qutenza offers the potential for long-lasting pain relief from a single, in-office application every three months. Due to its strength and potential side effects, its use is strictly controlled and administered only by healthcare professionals.
For more information on the mechanism of capsaicin, you can review this article from the National Institutes of Health: Topical capsaicin for pain management: therapeutic potential and mechanisms of action [1.5.1]
