Effects of Silodosin and Naftopidil on the Distal Ureter and Cardiovascular System in Anesthetized Dogs: Comparison of Potential Medications for Distal Ureteral Stone Passage

Silodosin: An Update on Efficacy, Safety and Clinical Indications in Urology

INTRODUCTION

Silodosin determines smooth muscle relaxation in bladder and prostate tissues, increases bladder blood flow in conditions of chronic bladder ischemia and regulates the activity of transcriptional factors responsible for stromal growth and prostate hyperplasia. Phase III trials have already demonstrated the efficacy and safety of silodosin in the treatment of patients bothered by lower urinary tract symptoms (LUTS) secondary to benign prostatic hyperplasia (BPH).

OBJECTIVE

We aimed to describe the rationality for the use of silodosin and to summarize the current literature on the use of Silodosin for the treatment of LUTS.

METHODS

PubMed and Web of Science were queried with the terms: 'silodosin' in combination (AND) with the terms 'lower urinary tract symptoms', 'LUTS', 'pathophysiology', 'symptoms' OR 'therapy'. Studies published in the last 10 years (2007-2017) in adults and core clinical journals in English were included.

RESULTS

Silodosin 8 mg once-daily was superior to placebo in improving IPSS total score, voiding subscore, storage subscore and QoL score, and at least as effective as tamsulosin 0.4 mg once-daily in all the efficacy analyses. In addition, studies assessing the effect on urodynamic parameters showed that silodosin determined a higher improvement in the bladder outlet obstruction index compared to other alpha1 adrenergic receptor antagonists. Concerning the safety profile, long-term data (after 9 months of treatment) confirmed the limited effect of silodosin on the cardiovascular and gastrointestinal systems. Although ejaculatory disorders represented the main complaint of patients taking silodosin, the discontinuation rate due to this condition remained low even in a long-term follow-up study (7.5%). Encouraging findings showed that silodosin may be administered as a medical expulsive therapy for promoting spontaneous stone passage of distal ureteral stones < 10 mm, to relieve LUTS in patients who underwent prostate cancer brachytherapy and to increase the likelihood of successful trials without a catheter in patients experiencing acute urinary retention.

CONCLUSION

Silodosin is one of the drugs approved for the treatment of BPH, being highly effective in improving not only LUTS but also urodynamic parameter impairments secondary to BPH. Moreover, it has shown efficacy as medical expulsive therapy for distal ureteral stones in previous prospective randomized trials.

FUNDING

Sponsorship for this study and article processing charges were funded by Recordati.

Effects by silodosin on the partially obstructed rat ureter in vivo and on human and rat isolated ureters

BACKGROUND AND PURPOSE

α1 -adrenoceptor (-AR) antagonists may facilitate ureter stone passage in humans. We aimed to study effects by the α1 A -AR selective antagonist silodosin (compared to tamsulosin and prazosin) on ureter pressures in a rat model of ureter obstruction, and on contractions of human and rat isolated ureters.

EXPERIMENTAL APPROACH

After ethical approval, ureters of male rats were cannulated beneath the kidney pelvis for in vivo ureteral intraluminal recording of autonomous peristaltic pressure waves. A partial ureter obstruction was applied to the distal ureter. Mean arterial blood pressure (MAP) was recorded. Approximate clinical and triple clinical doses of the α1 -AR antagonists were given intravenously. Effects by the α1 -AR antagonists on isolated human and rat ureters were studied in organ baths.

KEY RESULTS

Intravenous silodosin (0.1-0.3 mg kg(-1) ) or prazosin (0.03-0.1 mg kg(-1) ) reduced obstruction-induced increases in intraluminal ureter pressures by 21-37% or 18-40% respectively. Corresponding effects by tamsulosin (0.01 or 0.03 mg kg(-1) ) were 9-20%. Silodosin, prazosin and tamsulosin reduced MAP by 10-12%, 25-26% (P < 0.05), or 18-25% (P < 0.05) respectively. When effects by the α1 A -AR antagonists on obstruction-induced ureter pressures were expressed as a function of MAP, silodosin had six- to eightfold and 2.5- to eightfold better efficacy than tamsulosin or prazosin respectively. Silodosin effectively reduced contractions of both human and rat isolated ureters.

CONCLUSIONS AND IMPLICATIONS

Silodosin inhibits contractions of the rat and human isolated ureters and has excellent functional selectivity in vivo to relieve pressure-load of the rat obstructed ureter. Silodosin as pharmacological ureter stone expulsive therapy should be clinically further explored.

Silodosin in the management of lower urinary tract symptoms as a result of benign prostatic hyperplasia: who are the best candidates

BACKGROUND

As the clinical effects of the available α1-adrenoceptors (ARs) blockers are usually considered comparable for treatment in patients suffering from lower urinary tract symptoms (LUTS) secondary to prostatic enlargement, officially recognised guidelines do not make specific recommendations regarding the choice of which agent should be considered according to the patient's characteristics.

AIM

To analyse data supporting the use of silodosin, a highly selective once-daily dosing α1-ARs blocker, in different daily clinical practice scenarios.

MATERIALS AND METHODS

A structured literature review was performed using data retrieved from articles assessing the role of silodosin in the management of LUTS secondary to benign prostatic hyperplasia (BPH). A literature search of English language publications was performed using MEDLINE(®) and Web of Science from 2000 to 2012 using the terms LUTS; BPH; silodosin; α1-ARs blockers. The papers with the highest level of evidence were identified and represent the basis of the present review.

RESULTS

Available data coming from basic research analyses, randomised trials and prospective studies showed that silodosin is efficacious for the initial management of patients with LUTS. Clinical developmental safety data from patients receiving silodosin with concomitant antihypertensive therapy do not indicate an increase in risk of orthostatic hypotension. In this context, a recent study demonstrated that silodosin can be safely administered to patients who are consensually assuming phosphodiesterase type 5 inhibitors. A recent randomised crossover study comparing the efficacy of silodosin and tamsulosin in patients with LUTS showed that further significant improvement was observed after switching to silodosin treatment, while worsening or little improvement was observed after switching to tamsulosin treatment. Preliminary results seem to demonstrate a potential role of silodosin in the treatment of chronic prostatitis/chronic pelvic pain syndrome and to facilitate ureteral stone passage, as well.

DISCUSSION

When considering the above cited pharmacological and clinical characteristics of the drug, silodosin can be considered in the following clinical scenario: patients suffering from moderate-severe nocturia, patients with low normal blood pressure levels and patients concomitantly treated with antihypertensive medications, patients concomitantly treated with phosphodiesterase type 5 inhibitors, patients not satisfied (for efficacy or tolerability) with previous treatment with other α1-ARs blockers.

CONCLUSION

Silodosin is efficacious for the initial management of patients with LUTS. Silodosin has a good cardiovascular safety profile and can be considered an option in patients with cardiovascular co-morbidities. It seems to be especially beneficial in patients with nocturia alone or presenting with the symptomatic trial nocturia-frequency-incomplete emptying. Patients on phosphodiesterase type 5 inhibitors treatment can be safely managed with silodosin.