Products
Capsaicin is commercially available in many countries as creams and patches, among other products. Capsaicin cream at 0.025% and 0.075% is not commercially available as a finished drug product. It is produced as a magisterial formulation in pharmacies. See also under the article capsaicin cream.
Structure and properties
Capsaicin (C18H27NO3, Mr = 305.4 g/mol) exists as a white, crystalline, and odorless powder that is practically insoluble in water. The lipophilic vanillylamide occurs naturally in -species such as cayenne pepper of the Solanaceae family.
Effects
Capsaicin (ATC N01BX04) has initial warming, circulatory, irritant, burning, vasodilator, and pruritic properties. On the other hand, with prolonged use, it has analgesic, antinociceptive and antipruritic effects. The drug target of capsaicin is TRPV1 (Transient Receptor Potential Vanilloid 1), a non-selective cation channel that is also activated by heat and protons. In skin, TRPV1 is found in the cell membrane of sensory nerve fibers. Capsaicin is an agonist to this ion channel. It activates TRPV1-expressing nociceptors and stimulates the release of neuropeptides such as substance P. This initially leads to the adverse effects mentioned. This is followed by a refractory period with reduced sensitivity and, after repeated applications, permanent desensitization. This causes insensitivity of the nerve fibers to various stimuli and leads to pain relief.
Indications for use
Indications for use include:
- For the treatment of peripheral neuropathic pain (nerve pain, neuralgia) in adults. These include postherpetic neuralgia and diabetic neuropathy.
- For the symptomatic treatment of pain in osteoarthritis, back pain.
- Nerve disorders (neuropathies).
- Idiopathic pruritus.
- Joint and muscle pain, neck tension, rheumatic complaints.
Capsaicin is studied and used for numerous other applications, for example, for burning of the oral mucosa, headaches, paresthesias, allergic rhinitis, itching and psoriasis. Corresponding preparations are also used as aphrodisiacs, doping agents in equestrian sports, as pepper sprays, chemical weapons, repellents against dogs, squirrels in the park and sharks when diving. Cayenne pepper is a popular spice (e.g. Tabasco).
Dosage
The application depends on the product.
Contraindications
- Hypersensitivity
- Application to injured, irritated or diseased skin.
- Contact with the eyes, respiratory tract or mucous membrane.
- Pregnancy, lactation
- Babies, children
Full precautions can be found in the SmPC.
Interactions
Interactions are possible with other topically administered drugs that irritate the skin.
Adverse effects
The most common possible adverse effects include local reactions such as a burning sensation, pain, redness of the skin, and itching. These symptoms usually subside after a few days. Capsaicin may cause a temporary increase in blood pressure and irritate the respiratory tract. Ingestion of high doses of cayenne bell pepper is associated with a burning sensation, tearing, runny nose, difficult urination, and a burning sensation during defecation within one to two days (“peppers burn twice”). Ingestion of capsaicin may cause breathing and swallowing difficulties.