Capsaicin

• Neuropathic Pain:
  Used for symptomatic relief of neuropathic pain, including postherpetic neuralgia and diabetic peripheral neuropathy.
• Osteoarthritis Pain:
  Indicated for relief of mild to moderate localized pain associated with osteoarthritis.
• Musculoskeletal Pain:
  Used for temporary relief of minor aches and pains of muscles and joints due to strains, sprains, and arthritis.
• Psoriasis:
  Topical capsaicin may be used off-label for symptomatic relief of pruritus and pain in psoriasis.
• Other Off-label Uses:
  Management of chronic pruritus and cluster headaches (nasal formulation).

• Topical Creams/Ointments (0.025% to 0.1%):
  Apply thinly to affected area 3 to 4 times daily. Wash hands thoroughly after application.
• Patch (8%):
  For postherpetic neuralgia, a single application of an 8% capsaicin patch for 30 to 60 minutes under medical supervision. May be repeated every 3 months or as needed.
• Nasal Spray:
  Used for cluster headache; dose varies, typically 0.1% solution, administered into each nostril as directed.
• Precautions:
  Avoid contact with eyes and mucous membranes. Do not apply to broken or irritated skin.
• Pediatrics:
  Safety not established; use generally not recommended.
• Elderly:
  Use caution due to potential skin sensitivity.

Capsaicin is a naturally occurring alkaloid derived from chili peppers that selectively binds to the transient receptor potential vanilloid 1 (TRPV1) receptor on nociceptive nerve fibers. This binding initially causes depolarization and release of substance P, a neuropeptide involved in pain transmission. Repeated or prolonged exposure depletes substance P and desensitizes sensory neurons, leading to decreased pain signaling and analgesia in the treated area.

• Absorption:
  Minimal systemic absorption through intact skin; systemic bioavailability is negligible with topical use.
• Distribution:
  Primarily localized effect at application site.
• Metabolism:
  Metabolized hepatically after systemic absorption (very limited).
• Elimination:
  Primarily renal excretion of metabolites.
• Onset of Action:
  Initial burning sensation within minutes; analgesic effect develops over days to weeks with repeated use.
• Duration:
  Analgesic effects can persist for weeks after discontinuation due to nerve desensitization.

• Pregnancy:
  No well-controlled studies in pregnant women; topical use generally considered low risk due to minimal systemic absorption but should be used only if clearly needed.
• Lactation:
  Unknown if excreted in breast milk; caution advised. Avoid application on large areas during breastfeeding.

• Primary: Analgesic
• Subclass: Topical sensory neuron desensitizer

• Known hypersensitivity to capsaicin or formulation excipients.
• Open wounds, broken, or inflamed skin at application site.
• Use contraindicated in patients with severe skin conditions in the treatment area.

• Avoid contact with eyes, mucous membranes, and sensitive areas.
• Initial burning or stinging sensation common; usually diminishes with continued use.
• Use with caution in patients with dermatologic conditions.
• Monitor for allergic reactions or severe skin irritation.
• Not for systemic pain or deep tissue pain.
• Keep out of reach of children.

Common:

• Local burning, stinging, or itching sensation at application site
• Erythema and mild skin irritation
• Dryness or peeling of skin

Rare/Serious:

• Severe dermatitis or allergic contact dermatitis
• Urticaria
• Respiratory irritation with nasal formulations

• Minimal systemic absorption reduces interaction potential.
• Concomitant use with other topical irritants may increase skin irritation.
• Avoid simultaneous use with topical anesthetics at the same site.

• Recent clinical guidelines endorse capsaicin 8% patches as an effective option for localized neuropathic pain after failure of first-line treatments.
• Updated safety recommendations emphasize careful application and avoidance of mucous membranes.
• New formulations and delivery methods under investigation for improved tolerability.

• Store at controlled room temperature, 20°C to 25°C (68°F to 77°F).
• Protect from light and moisture.
• Keep container tightly closed.
• Keep out of reach of children.