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

Capsaicin is a specific neurotoxin for type C nonmyelinated vesical afferent fibres involved in the transmission of nociceptive stimuli and reorganization 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 bladder hypersensitivity or bladder hyperactivity. Ten clinical trials document the efficacy and safety of vesical instillation capsaicin in 200 patients with neurological or non-neurological lower urinary tract symptoms. The objective of this review is to analyse these various publications in order to define the indications and practical conditions of intravesical instillation of capsaicin. The value of intravesical capsaicin in neurogenic bladder hyperactivity has been clearly demonstrated. In non-neurological indications, the diversity of instillation protocols and the heterogeneity of the evaluation parameters complicate analysis of the results. Repeated low-dose capsaicin appears to be useful in bladder hyperactivity, but the value of capsaicin is uncertain in idiopathic detrusor instability. Transient adverse effects are almost systematically observed after intravesical capsaicin. The short-term and medium-term local histological safety appears to he satisfactory, but needs to be documented in the long-term.