TOPICAL CAPSAICIN - A REVIEW OF ITS PHARMACOLOGICAL PROPERTIES AND THERAPEUTIC POTENTIAL IN POSTHERPETIC NEURALGIA, DIABETIC NEUROPATHY ANDOSTEOARTHRITIS

Capsaicin, the active principle of hot chilli pepper is thought to sel ectively stimulate unmyelinated C fibre afferent neurons and cause the release of substance P. Prolonged application of capsaicin reversibly depletes stores of substance P, and possibly other neurotransmitters, from sensory nerve endings. This reduces ol abolishes the transmissio n of painful stimuli from the peripheral nerve fibres to the higher ce ntres. In clinical studies of patients with post-herpetic neuralgia, d iabetic neuropathy or osteoarthritis, adjunctive therapy with topical capsaicin achieved better pain relief than its vehicle in most studies . In a single trial, topical capsaicin demonstrated similar efficacy t o oral amitriptyline in patients with diabetic neuropathy. Topical cap saicin is not associated with any severe systemic adverse effects. How ever stinging and burning, particularly during the first week of thera py, is reported by many patients. Topical capsaicin merits considerati on as adjuvant therapy in conditions such as post-herpetic neuralgia, diabetic neuropathy and osteoarthritis, where the pain can be chronic and difficult to treat.