Tamsulosin in men with confirmed bladder outlet obstruction: a clinical and urodynamic analysis from a single centre in New Zealand
Authors: Arnold E.P. 
Published: March 2003

Objective To evaluate the clinical and pressure‐flow effects of tamsulosin 0.4 mg once daily in patients with lower urinary tract symptoms (LUTS) caused by benign prostatic obstruction (BPO), as documented by pressure‐flow studies performed according to a standardized protocol in one centre.

Patients and methods A single‐centre study was conducted with an open‐label design comprising a 2‐week, single‐blind, placebo run‐in period and a 12‐week active treatment period with tamsulosin 0.4 mg once daily. Eligible patients were men (aged  45 years) with LUTS (total International Prostate Symptom Score, IPSS,  13) with a free‐flow maximum urinary flow rate (Qmax) of  4 mL/s for a voided volume of  120 mL. After the 2‐week placebo run‐in period, only patients with BPO (i.e. in the obstructed zone of the Abrams‐Griffiths, AG, nomogram) received active treatment with tamsulosin. The two primary efficacy variables were the change in detrusor pressure at maximum flow (PdetQmax) and the total IPSS, from baseline to endpoint. A standardized protocol was used for all pressure‐flow studies.

Results In all, 42 patients were enrolled into the 2‐week placebo run‐in period, after which 30 received active treatment with tamsulosin 0.4 mg once daily. All 12 patients (29%) who discontinued during the placebo run‐in period failed to fulfil the pressure‐flow entry criterion of confirmed obstruction. The 30 patients who received tamsulosin had a high mean PdetQmax (82.1 cm H2O) and high mean AG number (68.1) at baseline, as would be expected in obstructed patients. Tamsulosin produced a significant reduction in mean PdetQmax (− 10.6 cm H2O or −13%; P = 0.005 vs baseline). The mean AG number decreased accordingly (− 15.5 points or −23%; P < 0.001 vs baseline). The pressure‐flow mean Qmax was increased by 2.5 mL/s (36%) from 7.0 mL/s at baseline (P = 0.002 vs baseline). Urodynamic improvements were accompanied by a good symptomatic response; the mean total IPSS was reduced by 6.7 points from a baseline value of 18.1 (− 37%, P < 0.001 vs baseline). At the endpoint, 67% of patients had a clinically significant symptomatic response (defined as a decrease in total IPSS of  25% from baseline). Twenty‐six patients (87%) were either slightly improved (13) or were much improved (13) in the opinion of the investigator. Twelve patients with LUTS who were unobstructed after the 2‐week placebo run‐in (PdetQmax 44.1 cm H2O) received tamsulosin treatment outside of the study protocol. Although these patients had no decrease in mean PdetQmax, the magnitude of the symptomatic response (decrease in total IPSS −6.4 or −34%, P = 0.001) was comparable with that in unobstructed patients; the free‐flow Qmax was also significantly improved. Possibly or probably drug‐related adverse events were reported in nine patients; one discontinued tamsulosin treatment because of a serious adverse event.

Conclusion Tamsulosin 0.4 mg once daily can produce a significant decrease in detrusor pressure, increase in flow rate and a symptomatic improvement in patients with LUTS and confirmed obstruction. Patients with LUTS who are unobstructed and have a low initial detrusor pressure appear to have no improvement in detrusor pressure, but have similar clinical responses to those in obstructed patients. Pressure‐flow studies can be reserved for those patients with LUTS who fail to respond to these agents and in whom further diagnosis and management is warranted.