Dasgupta, Prokar; (2000) Towards an understanding of the role of intravesical capsaicin in the treatment of detrusor hyperreflexia. Doctoral thesis (Ph.D.), University College London (United Kingdom).

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Abstract

Capsaicin is the pungent extract of red-hot chilli peppers. Chillies were grown as early as 5000 BC in Mexico and have been used medicinally, for a variety of seemingly unrelated disorders, for thousands of years. Animal experiments have demonstrated that capsaicin blocks a C-fibre mediated micturition reflex in spinal cats. The aim of this study was to investigate its role in the treatment of detrusor hyperreflexia due to spinal cord disease. Intravesical instillations of 1-2 mmol/l of capsaicin, dissolved as a powder in 30% alcohol in saline, were effective in 70% of patients with refractory detrusor hyperreflexia. After initial deterioration in voiding symptoms capsaicin caused an increase in the functional bladder capacity and decrease in the amplitude of hyperreflexic detrusor contractions. The beneficial effect of a single instillation lasted for 3-6 months. Even after repeated instillations over 5 years there was no evidence of pre-malignant or malignant changes in biopsies from bladders thus treated. Suprapubic discomfort during instillations was reduced by the prior use of intravesical lignocaine (40ml of 2% for 20 mins) or by anaesthetising the bladder with iontophoresis of intravesical lignocaine (electromotive drug administration) before capsaicin. Cryostat sections of flexible cystoscopic biopsies before and 6 weeks after capsaicin treatment were stained with the neuronal markers S 100 and PGP 9.5. By using computerized image analysis of lamina propria nerve densities ('MiniMOP' for S 100 and 'Seescan' imaging for PGP 9.5) it was found that intravesical capsaicin caused a reduction in densities of the presumptive sensory suburothelial nerves. Early data using electron microscopy seemed to show a reduction in the densities of clear and dense cored vesicles after capsaicin treatment. These findings indicate that capsaicin causes a sensory denervation the bladder in these patients. Intravesical capsaicin is a significant advance in Uro-Neurology and is likely to lead to the application of other vanilloids, such as resiniferatoxin, in the treatment of detrusor hyperreflexia.

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