Repeated injections of botulinum toxin A into the detrusor muscle have a persistent beneficial effect on neurogenic detrusor overactivity, according to a study by French and Swiss investigators.


Clinically, the repeated injections were as efficient as the first injection, the authors wrote. Urodyna-mically, the repeated injections remained as effective on the maximal cystometric bladder capacity and maximal detrusor pressure, and did not have any negative effects on bladder compliance.

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The investigators studied 17 patients who had a total of 91 injections, for a mean of 5.4 per patient. The mean interinjection interval was 262 days between the first and second injection, 265.8 days between the second and third, 230.8 days between the third and fourth, 274.6 days between the fourth and fifth, 275.4 days between the fifth and sixth, and 273.5 days between the sixth and seventh.


The mean number of incontinence episodes per day declined from 2.6 at baseline to 0 after the first injection and remained at 0 after the last injection. After the first injection, the mean maximal cystometric bladder capacity rose significantly from 248.8 to 499.1 mL. After the last injection, the maximal cystometric bladder capacity was 461.8 mL, which was significantly higher than baseline.


Repeated injections did not induce greater increases in maximal cystometric bladder capacity than after the first injection. After the first injection, the mean reflex volume increased significantly from 205.9 to 351.2 mL; after the last injection, it was 381.4 mL. The researchers observed a significant decrease in maximal detrusor pressure from 75.5 cm H2O at baseline to 28.8 cm H2O after the first injection and 27.4 cm H2O after the last injection. The difference in pressure values after the first and last injections were not significant.