Sufferers of the embarrassing problem of overactive bladder may be heartened to hear about new data from an ongoing study into a promising new treatment.

People with overactive bladder often have the sudden and unstoppable need to urinate, even when their bladders contain only a small amount of urine.

The condition, which typically affects people in older age, is primarily a problem of the nerves and muscles of the bladder, particularly the detrusor, one of the bladder's major muscles.

While there are medications available that relax bladder muscles, and exercises that can help strengthen them, there have been few effective long-term treatments.

But recently, researchers have begun experimenting with a treatment involving botulinum toxin (Botox) injection into the detrusor muscle. Now, European researchers are offering data that's studying the long-term efficacy of the treatment.

In a study presented this week at the 25th Annual European Association of Urology (EAU) Congress, Dr. Daniel Max Schmid, of the department of urology at University Hospital Zurich, in Switzerland, reported the results of an eight-year follow-up of the treatment.

The study enrolled 240 patients with overactive bladder who were injected with 100 units of botulinum-A toxin (BoNT-A). Within two weeks, they found:

• 84 per cent of patients experienced significant improvement of their bladder function
• 75 per cent reported that urgency completely disappeared
• 85 per cent reported that incontinence was no longer a problem.

As well, pad usage among the patients dropped from an average of five pads a day each to 0.5 pads per day. Frequency of urination and nighttime urination decreased by 50 per cent, and most participants were able to go longer between urinations.

While 16 patients reported poor benefit from the treatment, no further therapy was required by 30 per cent of patients.

Several patients needed additional treatment: 27.5 per cent required an additional injection, with a mean interval between treatments of 13 months. Fifteen patients received a third BoNT-A injection, which had a longer-lasting effect (5.5 months longer between the second and third treatments than between the first and second injections). Nine patients received a fourth injection, and one patient has received seven injections.

Side effects included 20 urinary infections among the 240 patients, and seven temporary urine retentions.

Nevertheless, Dr. Schmid concluded that the Botox treatment was a safe, long-term treatment for patients with severe overactive bladder.

He noted that although some patients required subsequent injections to maintain symptom-free status, the period of effectiveness lengthened with repeated injections, and the muscle and bladder were not damaged with repeated treatments.