Overactive Bladder Study Finds Fewer Botox Injections Eases Pain Without Sacrificing Treatment Effectiveness

Patients with overactive bladder and urinary incontinence experience significantly less pain and just as much symptom relief when receiving fewer bladder injections of Botox, according to a trial led by Houston Methodist Hospital.

The randomized, single-blind trial evaluated whether reducing the number of injection sites from 20 to five would improve patient comfort and satisfaction during outpatient treatment for neurogenic lower urinary tract dysfunction (NLUTD) and idiopathic overactive bladder (IOAB). It also assessed whether the new approach would deliver equivalent therapeutic benefits.

"Our study shows that five injections are as effective with less discomfort for the patient," said Dr. Rose Khavari, the trial's principal investigator and a professor of urology at Houston Methodist. "The Botox spreads within the bladder regardless of how many places it's injected. It's like taking a pill with one cup of water versus two — the dose is the same."

Dr. Khavari called bladder Botox a game-changer for people with bladder dysfunction who have not responded to medication. But she noted that each needle entry adds time, a small amount of risk and pain in patients, most of whom are awake during the procedure.

Both NLUTD and IOAB can cause urinary urgency, frequency and urge-related incontinence, significantly impacting patients' quality of life. Since its FDA approval early in the previous decade, bladder Botox has significantly improved symptoms in patients with both conditions.

The trial, Smarter Shots: Optimizing the Injection Schema for Higher Doses of OnabotulinumtoxinA in the Office Setting, enrolled 78 adult patients who were randomized to receive their recommended total dose (200-300 units) in either five or 20 injections in the bladder wall. All patients were treated under local anesthesia.

The results showed no difference between groups in their willingness to repeat the procedure — the trial's primary outcome — suggesting that therapeutic effectiveness remained intact regardless of the number of injections. However, pain scores told a different story. The average post-procedural pain score was significantly higher in the 20-injection group (3.39/10) compared to the five-injection group (0.57/10), with some patients in the 20-injection arm reporting maximum pain scores of 10.

There were no statistically significant differences between groups in adverse events, urinary symptoms or rates of urinary tract infections. At 12 months, more patients in the five-injection group had returned for follow-up injections, reinforcing the idea that reduced procedural discomfort may increase long-term adherence.

The trial was conducted at Houston Methodist and supported in part by NIH funding through the CAIRIBU (Collaborating for the Advancement of Interdisciplinary Research in Benign Urology) initiative. Dr. Khavari emphasized the roles of Dr. Annie Chen, URPS fellow, who helped design the study, perform data analysis and present results, and study coordinators Hamida Rajab and Julu Benoy, who fulfilled enrollment objectives well ahead of schedule.

"This research underscores our commitment to patient-centered care," Dr. Khavari said. "We're focused not only on whether this treatment works for overactive bladder, but also on how its delivery can be optimized to reduce its impact on the patient. That's the kind of leadership that advances everyday urologic care."