Intravesical instillations of capsaicin in urology: from pharmacological principles to therapeutic applications.

Capsaicin is a specific neurotoxin for type C nonmyelinated vesical afferen t fibres involved in the transmission of nociceptive stimuli and reorganiza tion of voiding reflexes in disease. The presence of afferents sensitive to vanilloid substances in the human bladder suggests the potential value of intravesical instillations of capsaicin in patients with symptoms of bladde r hypersensitivity or bladder hyperactivity. Ten clinical trials document t he efficacy and safety of vesical instillation capsaicin in 200 patients wi th neurological or non-neurological lower urinary tract symptoms. The objec tive of this review is to analyse these various publications in order to de fine the indications and practical conditions of intravesical instillation of capsaicin. The value of intravesical capsaicin in neurogenic bladder hyp eractivity has been clearly demonstrated. In non-neurological indications, the diversity of instillation protocols and the heterogeneity of the evalua tion parameters complicate analysis of the results. Repeated low-dose capsa icin appears to be useful in bladder hyperactivity, but the value of capsai cin is uncertain in idiopathic detrusor instability. Transient adverse effe cts are almost systematically observed after intravesical capsaicin. The sh ort-term and medium-term local histological safety appears to he satisfacto ry, but needs to be documented in the long-term.