Intravesical Capsaicin

Capsaicin is an extract from red pepper and exerts a selective action on certain sensory nerves, most notably those involved in reflex contractions of the bladder after spinal cord injury.

Discussion

One RCT (Giannantoni et al. 2002) and one pre-post study (Igawa et al. 2003) evaluated the effect of capsaicin. Capsaicin exerts a selective action on sensory nerves involved in reflex contractions of the bladder after SCI. Igawa et al. (2003) demonstrated that intravesical capsaicin decreased episodes of AD in people with SCI during catheterization, thereby suggesting its therapeutic potential for both AD and detrusor hyperreflexia in individuals with SCI. Moreover, Giannantoni et al. (2002) used an analogue of capsaicin (resiniferatoxin RXT) that is more than 1,000 times more potent in desensitizing C-fiber bladder afferents, and found reduced episodes of AD. Additionally, Giannantoni et al. (2002) found that intravesical administration of resiniferatoxin within 60 days of treatment did not cause the inflammatory side effects often seen with capsaicin, suggesting superior urodynamic results and clinical benefits. However, long-term effects of capsaicin or resiniferatoxin on AD have not been evaluated.

Conclusion

There is level 1 evidence (from 2 RCTs) (Kim et al. 2003; Giannantoni et al. 2002) that intravesical resiniferatoxin is effective for reducing episodes of AD in patients with SCI.

There is level 1 evidence (from 1 RCT) (Giannantoni et al. 2002) that intravesical resiniferatoxin is more effective than intravesical capsaicin.

There is level 4 evidence (from 1 pre-post study) (Igawa et el. 2003) that intravesical capsaicin is effective for reducing episodes of AD in SCI.