A 4-week, Double-blind, Randomized, Comparative and Multi-center Clinical Trial to Evaluate the Efficacy and Safety of Silodosin in the Treatment of Natural Expulsion in Patients With Ureteral Stones.

Lower and mid ureteral calculi, accounting for approximately 70% of ureteral calculi, has a high chance of successful treatment thanks to ureteroscopic lithotripsy or extracorporeal shock wave lithotripsy (ESWL)1-3), but at the same time have problems of postprocedural complications and high expenses4). A lower ureteral calculus, which measures 5 millimeters and less, may be easily expelled by symptomatic therapy. Actually, it has about a 50% chance of successful expulsion5). However, a complication such as urinary tract infection or hydronephrosis or persistent pain may occur before it is expelled. Thus, it is imperative to minimize the occurrence of complications in the process of expectant treatment and also to reduce the time required to expel calculi.

It has been recently reported that pharmacotherapy is adhibited to the expulsion of urinary calculi and the relief of pain. The migration of ureteral calculi is influenced by both the calculus and the ureter. In the case of the calculus, size, shape, number and location influence it. In regard to the ureter, it is significantly influenced by the cramp of the ureteral smooth muscle, the edema of the ureteral submucosa, the pain caused by the calculus and the activities of adrenoreceptors6).

Pharmacotherapy is to relieve ureteral obstruction and thus to expel urinary calculi easily. Ureteral obstruction, caused by urinary calculi, obtunds ureteral peristalsis but strengthens ureteral contraction, which may cause urinary retention or regurgitation7-8). In this connection, studies have been conducted as to methods to reduce abnormal urinary reaction caused by urinary calculi and to smoothen uroflow. Currently, hormone drugs including hydroxyprogesterone, prostaglandin synthetase inhibitors, calcium-channel antagonists, α1-blockers and steroid drugs are used to expel urinary calculi and to suppress pain. The guidelines on urinary calculi, drawn up in 2007, recommend using α-blockers as they are superior to other drugs in efficacy9-12).

The drug to be used in this clinical trial, silodosin, was registered under the proprietary name of 'THRUPAS® Capsule 4mg' and is being marketed after being authorized by Korea Food and Drug Administration (FDA), which selectively acts on the α1A-adrenoreceptor.

This clinical trial is to evaluate the efficacy of silodosin, a selective α1A-blocker, on calculous expulsion in expectant treatment for patients with lower and mid ureteral calculi.