RELIEF OF PAIN FOLLOWING INTRAVESICAL CAPSAICIN IN PATIENTS WITH HYPERSENSITIVE DISORDERS OF THE LOWER URINARY-TRACT

We have extended our earlier observations on pain relief produced by i ntravesical instillation of capsaicin (10 muM in saline) in patients w ith hypersensitive disorders of the lower urinary tract. Patients in g roup A (n = 15) received intravesical capsaicin on days 0, 14 and 28: on each occasion the drug produced a warm or burning sensation, reduct ion in bladder capacity and a delayed, transient improvement or disapp earance of symptoms. Patients in group B (n = 5) received intravesical capsaicin (10 muM at cystometry) 3 times on day 0. The initial sensat ion of warmth was experienced on each occasion, indicating that no sig nificant desensitisation has been produced by the first instillation. Clinical improvement similar to that found in group A was observed. Th ree patients (group C) received warm saline (42-degrees-C) at cystomet ry. This produced a pricking sensation, no change at cystometry and no subjective clinical improvement. Apart from the initial sensation of warmth, no patient in group A or B experienced side effects, either lo cal or systemic. These findings confirm that intravesical instillation of capsaicin has a beneficial effect on patients with hypersensitive bladder disorders. Counter-irritation rather than desensitisation of p rimary afferents could be a possible mechanism of action. Further stud ies are needed to establish whether the intravesical administration of capsaicin or capsaicin-like agents represents a new form of treatment for relief of bladder pain.