Intraprostatic Injection of Botulinum Toxin for the Management of Benign Prostatic Hyperplasia (MIST)

Benign prostatic hyperplasia (BPH) and lower urinary tract symptoms are bothersome and costly conditions affecting nearly half of men older than age 50 years and 90% of men older than age 80. In the search for more effective noninvasive therapies, the role of the neural activity in BPH has been studied. Botulinum toxin injection has been used for several urological conditions including voiding dysfunction, and studies have shown that intraprostatic injection may be beneficial in lower urinary tract symptoms secondary to BPH.

Eligible men were randomized in a 1:1 ratio to a 100 or a 300 U dose of onabotulinum toxin A. The study was double-blind as to the toxin dose. The drug was injected transrectally into the prostatic peripheral transitional zone with ultrasound guidance. It was administered as 2 cc per lobe in 1 ml aliquots at 2 injection sites for a total of 4 sites.

Men were contacted by telephone at 1 week after treatment, and evaluated in person at 1, 2, 3, 6, 9 and 12 months. Uroflowmetry, vital signs, AUASI and medical conditions were collected or performed at baseline and each visit; transrectal ultrasound and questionnaires on the impact of BPH, bladder function, erectile function and ejaculatory function were administered at baseline, and 3 and 12 months; bladder ultrasound was performed at baseline and 12 months; and physical and digital rectal examination, and prostate specific antigen were determined at baseline, and at 3, 6 and 12 months.