Drug Monograph
Silodosin (Rapaflo)
silodosin
Pharmacokinetic Profile
Half-Life
5–13 h (parent); ~24 h (active glucuronide)
Metabolism
UGT2B7 (glucuronidation), CYP3A4, ADH/ALDH
Protein Binding
~97%
Bioavailability
~32% (oral, fed)
Volume of Distribution
49.5 L
Clinical Information
Drug Class
Alpha-1A adrenergic antagonist
Available Doses
4 mg, 8 mg capsules
Route
Oral
Renal Adjustment
Yes — reduce to 4 mg if CrCl 30–50; CI if <30
Hepatic Adjustment
CI in severe (Child-Pugh ≥10)
Pregnancy
Category B (not indicated in women)
Lactation
Not applicable (male-only indication)
Schedule / Legal Status
Rx only (not scheduled)
Generic Available
Yes
Indications
| Indication | Approved Population | Therapy Type | Status |
|---|---|---|---|
| Signs and symptoms of benign prostatic hyperplasia (BPH) | Adult males | Monotherapy | FDA Approved |
Silodosin is a highly selective alpha-1A adrenergic receptor blocker developed specifically for lower urinary tract symptoms associated with BPH. Its unprecedented selectivity for the alpha-1A subtype (162-fold over alpha-1B) means it predominantly relaxes prostatic and urethral smooth muscle with comparatively less effect on vascular smooth muscle. Clinical trials demonstrate rapid onset of symptom improvement, with measurable increases in peak urinary flow rate within 2–6 hours of the first dose and significant IPSS reductions within 3–4 days. Silodosin is not indicated for the treatment of hypertension.
Off-Label Uses
Distal ureteral stone expulsion (medical expulsive therapy): Multiple randomised controlled trials and meta-analyses support silodosin 8 mg once daily to facilitate passage of distal ureteral stones <10 mm. One meta-analysis of six RCTs (n = 916) found silodosin significantly increased stone expulsion rates compared to controls (OR 2.16, 95% CI 1.62–2.86). The AUA and EAU guidelines recommend alpha-blockers as MET for distal ureteral stones. Evidence quality: Moderate.
Dosing
Adult Dosing — By Clinical Scenario
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| BPH — standard therapy, normal renal function | 8 mg once daily | 8 mg once daily | 8 mg/day | Take with a meal; no titration needed Fixed-dose regimen; onset of symptom relief in 3–4 days |
| BPH — moderate renal impairment (CrCl 30–50 mL/min) | 4 mg once daily | 4 mg once daily | 4 mg/day | Exposure ~3-fold higher than normal function Monitor closely for orthostatic hypotension |
| BPH — mild renal impairment (CrCl 50–80 mL/min) | 8 mg once daily | 8 mg once daily | 8 mg/day | No dose adjustment needed |
| BPH — mild-to-moderate hepatic impairment (Child-Pugh A or B) | 8 mg once daily | 8 mg once daily | 8 mg/day | No dose adjustment needed PK not significantly altered in moderate hepatic impairment |
| Ureteral stone expulsion (off-label MET) | 8 mg once daily | 8 mg once daily | 8 mg/day | Discontinue after stone passage; typical duration 3–28 days Primarily studied for distal stones <10 mm |
| Patients with swallowing difficulty | 8 mg (sprinkle) | 8 mg (sprinkle) | 8 mg/day | Open capsule, sprinkle on applesauce (not hot), swallow within 5 min without chewing Bioequivalent to intact capsule; follow with 240 mL cool water |
Clinical Pearl — No Titration Required
Unlike older non-selective alpha-blockers (doxazosin, terazosin) that require gradual dose escalation, silodosin can be initiated at the full therapeutic dose of 8 mg without titration thanks to its high alpha-1A selectivity and minimal vascular alpha-1B blockade. Peak urine flow rate improvement is measurable within 2–6 hours of the first dose (FDA PI).
Pharmacology
Mechanism of Action
Silodosin is a competitive antagonist at alpha-1 adrenergic receptors with an exceptionally high binding selectivity for the alpha-1A subtype. Its alpha-1A-to-alpha-1B selectivity ratio is approximately 162:1, and its alpha-1A-to-alpha-1D ratio is approximately 55:1, making it the most alpha-1A-selective agent in clinical use. Alpha-1A receptors are the predominant subtype in the prostatic stroma, bladder neck, and prostatic urethra. By blocking these receptors, silodosin relaxes smooth muscle in the lower urinary tract, reducing the dynamic component of bladder outlet obstruction. This leads to improved urinary flow rate and reduced storage and voiding symptoms. The low affinity for alpha-1B receptors in peripheral vasculature accounts for the reduced cardiovascular effects relative to non-selective alpha-blockers. Emerging evidence also suggests silodosin may modulate afferent nerve signaling in the bladder, contributing to improvement in storage symptoms beyond simple smooth muscle relaxation.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | Bioavailability ~32%; Tmax ~2.6 h; food decreases Cmax 18–43%, AUC 4–49% | Must be taken with a meal to ensure consistent exposure and match clinical trial conditions; rapid absorption enables early symptom relief |
| Distribution | Vd = 49.5 L; protein binding ~97% (primarily to alpha-1 acid glycoprotein) | High protein binding limits free fraction; conditions altering AGP levels (inflammation, hepatic disease) may change free drug concentrations |
| Metabolism | UGT2B7 (glucuronidation to KMD-3213G, active), CYP3A4, alcohol/aldehyde dehydrogenases | Glucuronide metabolite (KMD-3213G) reaches 4x parent AUC with t½ ~24 h and retains partial alpha-1A activity; CYP3A4 inhibitors substantially increase exposure |
| Elimination | Feces 55%, urine 34%; t½ 5–13 h (parent), ~24 h (KMD-3213G) | Dual elimination pathway; in moderate renal impairment, AUC triples and half-life doubles — mandating dose reduction to 4 mg |
Side Effects
≥10%
Very Common
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Retrograde ejaculation / anejaculation | 28.1% | Most distinctive side effect of silodosin; results from alpha-1A-mediated relaxation of the vas deferens and bladder neck. Reversible on discontinuation. Not a safety concern, but a significant cause of non-adherence in sexually active men. |
1–10%
Common
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Dizziness | 3.2% | Typically occurs at treatment initiation; advise caution with driving and operating machinery in the first week |
| Diarrhea | 2.6% | Generally mild and self-limiting; rarely requires treatment modification |
| Orthostatic hypotension | 2.6% | Higher in patients ≥65 years and those on concomitant antihypertensives (3.4% vs general population); lower than non-selective alpha-blockers |
| Headache | 2.4% | Comparable to placebo incidence in extended studies; generally transient |
| Nasopharyngitis | 2.4% | Similar to placebo rate (2.2%); likely incidental rather than drug-related |
| Nasal congestion | 2.1% | Vasodilatory effect on nasal mucosa; typically mild |
| Insomnia | 1–2% | Reported more often than placebo; consider morning dosing if symptomatic |
| Abdominal pain | 1–2% | Mild gastrointestinal complaints, usually transient |
| Asthenia | 1–2% | Mild fatigue; usually resolves with continued therapy |
Serious
Serious (Regardless of Frequency)
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| Syncope | Rare (<1%) | First days of therapy | Discontinue if recurrent; evaluate for cardiac aetiology; counsel on hydration and positional changes |
| Priapism | Very rare (case report) | Any time during therapy | Urological emergency; permanent discontinuation; immediate aspiration/irrigation if >4 hours |
| Intraoperative Floppy Iris Syndrome (IFIS) | Rare (observed in open-label study) | During cataract surgery | Alert ophthalmologist before any planned cataract or intraocular surgery; surgical technique modification (iris hooks/dilator rings) may be needed. Note: stopping silodosin preoperatively may not eliminate risk. |
| Allergic reactions (including pharyngeal oedema, tongue swelling) | Very rare (postmarketing) | Any time | Permanent discontinuation; emergency airway management as needed; silodosin contraindicated with known hypersensitivity |
| Hepatotoxicity (jaundice, transaminase elevation) | Very rare (postmarketing) | Variable | Check LFTs; discontinue if clinically significant elevations; investigate alternative causes |
| Toxic skin eruption / purpura | Very rare (postmarketing) | Variable | Discontinue; dermatology referral; supportive care |
Discontinuation
Discontinuation Rates
Overall (12-Week Pivotal Trials)
6.4% vs 2.2% placebo
Top reason: Retrograde ejaculation (2.8%)
Long-Term Extension (40-Week Open-Label)
7.5% (de novo) vs 1.9% (continuing)
Top reason: Retrograde ejaculation; higher rates in treatment-naive patients
| Reason for Discontinuation | Incidence | Context |
|---|---|---|
| Retrograde ejaculation | 2.8% | Reversible on cessation; primary reason for treatment withdrawal despite not being a safety concern |
| Dizziness | <1% | Typically resolved with continued treatment in most patients |
| Orthostatic hypotension | <1% | More common in elderly and those on antihypertensives |
| Other reasons combined | ~1.6% | Includes diarrhea, headache, and rare individual events |
Managing Retrograde Ejaculation
Retrograde ejaculation occurs in approximately 28% of patients but led to discontinuation in only 2.8% in pivotal trials. This adverse effect is a direct pharmacological consequence of alpha-1A-mediated relaxation of the vas deferens and bladder neck, and resolves completely after stopping silodosin. Clinicians should proactively discuss this with patients before prescribing, emphasising its reversibility and lack of impact on fertility or orgasmic function. Data suggest that patients who experience ejaculatory changes actually demonstrate the greatest IPSS improvement (FDA PI).
Drug Interactions
Silodosin is metabolised primarily through UGT2B7-mediated glucuronidation with secondary contributions from CYP3A4 and alcohol/aldehyde dehydrogenases. It is also a substrate of the P-glycoprotein (P-gp) efflux transporter. In vitro data indicate silodosin does not significantly inhibit or induce CYP450 enzymes or P-gp, limiting the risk of silodosin affecting co-administered drugs. However, inhibitors of these pathways can substantially increase silodosin exposure.
Major
Strong CYP3A4 Inhibitors (e.g., ketoconazole, itraconazole, clarithromycin, ritonavir)
MechanismInhibition of CYP3A4 and P-gp reduces silodosin clearance
EffectKetoconazole 400 mg caused 3.8-fold increase in Cmax and 3.2-fold increase in AUC
ManagementCombination is contraindicated. Use an alternative antifungal, antibiotic, or antiretroviral that does not strongly inhibit CYP3A4.
FDA PI
Major
Strong P-glycoprotein Inhibitors (e.g., cyclosporine)
MechanismInhibition of P-gp efflux transporter increases silodosin absorption and reduces biliary clearance
EffectExpected significant increase in silodosin plasma concentrations (magnitude not formally studied)
ManagementConcomitant use not recommended. Consider tamsulosin or alfuzosin as alternatives where P-gp inhibition is unavoidable.
FDA PI
Major
Other Alpha-Adrenergic Blockers (e.g., tamsulosin, doxazosin, terazosin, alfuzosin)
MechanismAdditive alpha-1 blockade
EffectExpected potentiation of hypotension, dizziness, and syncope risk
ManagementCombination is not recommended. Select a single alpha-blocker agent.
FDA PI
Moderate
PDE5 Inhibitors (e.g., sildenafil, tadalafil, vardenafil)
MechanismBoth classes produce vasodilation through complementary mechanisms
EffectRisk of symptomatic hypotension; however, clinical studies with healthy volunteers showed no symptomatic events or dizziness
ManagementUse with caution. Ensure silodosin is at steady state before initiating PDE5 inhibitor at the lowest dose. Monitor for hypotension.
FDA PI
Moderate
Moderate CYP3A4 Inhibitors (e.g., diltiazem, erythromycin, verapamil)
MechanismPartial CYP3A4 inhibition increases silodosin concentrations
EffectModerate increase in silodosin exposure; clinical significance not fully characterised
ManagementUse with caution. Monitor for orthostatic symptoms, dizziness, and ejaculatory changes. Dose reduction may be considered.
FDA PI
Moderate
UGT2B7 Inhibitors (e.g., probenecid, valproic acid, fluconazole)
MechanismInhibition of the primary glucuronidation pathway of silodosin
EffectMay increase silodosin parent compound and/or alter glucuronide metabolite exposure
ManagementMonitor for adverse effects. Clinical impact not well defined; use clinical judgement.
FDA PI
Moderate
Antihypertensive Agents
MechanismAdditive blood-pressure lowering
EffectIn clinical trials, one-third of patients used concomitant antihypertensives; dizziness was 4.6% vs 3.8% and orthostatic hypotension 3.4% vs 3.2%
ManagementExercise caution. Monitor blood pressure and orthostatic symptoms, particularly at initiation.
FDA PI
Minor
Digoxin
MechanismEvaluated as a potential P-gp substrate interaction
EffectNo clinically relevant changes in digoxin pharmacokinetics observed in dedicated interaction study (n = 16)
ManagementNo dose adjustment needed for either drug.
FDA PIMonitoring
-
Blood Pressure
Baseline; at 1–2 weeks; then as indicated
Routine Assess sitting and standing blood pressure at initiation to detect orthostatic hypotension. Monitor more frequently in elderly patients and those on concomitant antihypertensives. -
Renal Function
Baseline; then annually or as indicated
Routine Creatinine clearance before initiation to determine dose. Repeat if renal function may have changed (intercurrent illness, nephrotoxin exposure) to verify continued appropriateness of 8 mg vs 4 mg dosing. -
BPH Symptom Assessment (IPSS)
Baseline; at 4–12 weeks; then every 6–12 months
Routine International Prostate Symptom Score to assess therapeutic response. Significant improvement expected within 3–4 days of initiation with full effect by 4–12 weeks. -
PSA
Baseline; then as per screening guidelines
Routine Silodosin does not significantly affect PSA levels. A normal PSA does not exclude prostate cancer. Rule out carcinoma before initiating alpha-blocker therapy. -
Ejaculatory Function
At each follow-up visit
Routine Proactively ask about ejaculatory changes. Document impact on quality of life and sexual satisfaction. Discuss reversibility if considering discontinuation. -
Liver Function Tests
If symptoms suggest hepatotoxicity
Trigger-based Postmarketing reports of jaundice and elevated transaminases. Check LFTs if patient develops unexplained jaundice, dark urine, or right upper quadrant pain. -
Cataract Surgery Planning
Before any intraocular procedure
Trigger-based Document silodosin use (current or past) and notify the ophthalmologist about IFIS risk. This applies even if silodosin has been discontinued, as the risk may persist.
Contraindications & Cautions
Absolute Contraindications
- Severe renal impairment (CrCl <30 mL/min) — Substantially increased exposure without adequate safety data at any dose
- Severe hepatic impairment (Child-Pugh ≥10) — Not studied in this population; pharmacokinetic behaviour unpredictable
- Concomitant strong CYP3A4 inhibitors (ketoconazole, itraconazole, clarithromycin, ritonavir) — 3.2–3.8-fold increase in silodosin exposure
- Known hypersensitivity to silodosin or any excipient — Postmarketing reports of pharyngeal oedema and tongue swelling
Relative Contraindications (Specialist Input Recommended)
- Planned cataract or intraocular surgery — IFIS risk persists even after discontinuation; ophthalmology should be informed and surgical technique may need modification
- Concomitant use of strong P-gp inhibitors (e.g., cyclosporine) — Not formally studied but expected to significantly increase exposure
- Patients with history of orthostatic hypotension or syncope — Higher risk population; consider alternative agents with lower alpha-1A selectivity
Use with Caution
- Moderate renal impairment (CrCl 30–50 mL/min) — Must use 4 mg dose; monitor for orthostatic hypotension and adverse effects
- Elderly patients (≥65 years) — Exposure increased ~15%; higher incidence of orthostatic effects reported in clinical trials
- Concomitant antihypertensive therapy — Slightly increased risk of dizziness (4.6% vs 3.8%) and orthostatic hypotension (3.4% vs 3.2%)
- Concomitant PDE5 inhibitors — Potential for symptomatic hypotension despite reassuring clinical study data in healthy volunteers
- Moderate CYP3A4 inhibitors (diltiazem, erythromycin, verapamil) — May increase silodosin exposure; magnitude not fully characterised
- Sexually active men who prioritise normal ejaculatory function — 28% incidence of retrograde ejaculation may impact adherence and satisfaction
FDA Class-Wide Regulatory Warning
Alpha-1 Adrenergic Blockers and Intraoperative Floppy Iris Syndrome
IFIS has been observed during cataract and other intraocular surgery in patients who are on, or have previously been treated with, alpha-1 adrenergic blockers. This class-wide warning applies to all alpha-1 blockers, including silodosin, tamsulosin, alfuzosin, doxazosin, and terazosin. Patients should inform their ophthalmologist about current or prior use of any alpha-blocker. Stopping the alpha-blocker before surgery has not been shown to eliminate IFIS risk. Surgical teams should be prepared to modify their technique accordingly.
Patient Counselling
Purpose of Therapy
Silodosin relaxes the muscles around the prostate and bladder neck to improve urinary flow and reduce symptoms such as hesitancy, weak stream, frequency, urgency, and nocturia. It does not shrink the prostate or change PSA levels and is not a treatment for prostate cancer. Symptom improvement typically begins within days but should be evaluated at 4–12 weeks to confirm adequate response.
How to Take
Take one capsule once daily with a meal, ideally in the morning. Swallow the capsule whole. If swallowing capsules is difficult, the capsule can be opened and the contents sprinkled onto a tablespoon of cool or room-temperature applesauce, then swallowed within five minutes without chewing, followed by a full glass of cool water. Do not subdivide the contents or save for later use.
Retrograde Ejaculation
Tell patient
About one in four men notice reduced or absent semen during orgasm. This is not harmful, does not affect orgasm, and reverses completely after stopping the medication. It occurs because the same muscles the drug relaxes for urinary improvement also control semen flow.
Call prescriber
If the ejaculatory change is distressing and affecting quality of life or sexual satisfaction, as the prescriber can discuss alternative medications that carry a lower risk of this effect.
Dizziness & Orthostatic Hypotension
Tell patient
Dizziness or light-headedness may occur, especially in the first few days. Rise slowly from sitting or lying positions. Avoid driving or operating heavy machinery until you know how the medication affects you. Stay well hydrated and avoid prolonged standing in hot environments.
Call prescriber
If you faint or feel like you are about to faint, experience chest pain, or if dizziness is persistent or worsening after the first week of treatment.
Cataract Surgery & Eye Procedures
Tell patient
If you are planning cataract surgery or any eye procedure, tell your eye doctor that you take (or have previously taken) silodosin. The medication can cause a condition during surgery where the iris becomes floppy, and your surgeon needs to know in advance to adjust their technique.
Call prescriber
Before scheduling any eye surgery, so the prescriber and ophthalmologist can coordinate care. Do not stop silodosin on your own before surgery without consulting your doctor.
Missed Dose
Tell patient
If you miss a dose, take it with your next meal. Do not take two capsules to make up for a missed dose.
Call prescriber
If you have been missing doses frequently, as your symptoms may return and an alternative dosing strategy or medication review may be warranted.
Allergic Reactions
Tell patient
Though rare, allergic reactions including skin rash, itching, swelling of the tongue or throat have been reported. These are serious and require immediate medical attention.
Call prescriber
Seek emergency medical help immediately if you develop swelling of the face, lips, tongue, or throat, difficulty breathing, or a severe skin rash.
Sources
Regulatory (PI / SmPC)
- Rapaflo (silodosin) capsules. Full Prescribing Information. Watson Pharmaceuticals, Inc. Revised 2013. FDA Label Primary source for all FDA-approved dosing, contraindications, adverse reaction rates, and pharmacokinetic parameters used throughout this monograph.
- Silodosin capsules. DailyMed label (Amneal Pharmaceuticals). Updated March 2021. DailyMed Current generic label confirming consistency of prescribing information with original NDA.
- Silodyx (silodosin). European Public Assessment Report — Product Information. European Medicines Agency. EMA SmPC European regulatory document providing additional pharmacokinetic data, including protein binding of the glucuronide metabolite and clinical study summaries.
Key Clinical Trials
- Marks LS, Gittelman MC, Hill LA, Volinn W, Hoel G. Rapid efficacy of the highly selective alpha1A-adrenoceptor antagonist silodosin in men with signs and symptoms of benign prostatic hyperplasia: pooled results of 2 phase 3 studies. J Urol. 2009;181(6):2634–2640. doi:10.1016/j.juro.2009.02.034 Pooled analysis of the two US pivotal trials (n = 923) demonstrating rapid IPSS improvement within 3–4 days and sustained efficacy through 12 weeks.
- Marks LS, Gittelman MC, Hill LA, Volinn W, Hoel G. Silodosin in the treatment of the signs and symptoms of benign prostatic hyperplasia: a 9-month, open-label extension study. Urology. 2009;74(6):1318–1322. doi:10.1016/j.urology.2009.04.089 Long-term safety extension providing 40-week data on adverse events, discontinuation rates, and sustained efficacy.
- Kawabe K, Yoshida M, Homma Y; Silodosin Clinical Study Group. Silodosin, a new alpha1A-adrenoceptor-selective antagonist for treating benign prostatic hyperplasia: results of a phase III randomized, placebo-controlled, double-blind study in Japanese men. BJU Int. 2006;98(5):1019–1024. doi:10.1111/j.1464-410X.2006.06448.x Japanese phase III trial (n = 457) comparing silodosin to tamsulosin and placebo, confirming efficacy and characterising the high rate of ejaculatory dysfunction.
Guidelines
- McVary KT, Roehrborn CG, Avins AL, et al. Update on AUA Guideline on the Management of Benign Prostatic Hyperplasia. J Urol. 2011;185(5):1793–1803. doi:10.1016/j.juro.2011.01.074 AUA guideline recommending alpha-blockers (including silodosin) as first-line pharmacotherapy for moderate-to-severe LUTS due to BPH.
- Gravas S, Cornu JN, Gacci M, et al. EAU Guidelines on Management of Non-Neurogenic Male Lower Urinary Tract Symptoms (LUTS), incl. Benign Prostatic Obstruction (BPO). European Association of Urology. 2024. EAU Guidelines Current European guideline positioning alpha-blockers as first-line and supporting MET with alpha-blockers for ureteral stones.
Mechanistic / Basic Science
- Yoshida M, Homma Y, Kawabe K. Silodosin, a novel selective alpha 1A-adrenoceptor selective antagonist for the treatment of benign prostatic hyperplasia. Expert Opin Investig Drugs. 2007;16(12):1955–1966. doi:10.1517/13543784.16.12.1955 Comprehensive mechanistic review covering silodosin’s receptor binding profile, 162-fold alpha-1A selectivity, and preclinical pharmacology.
- Lepor H. Alpha-blockers for the treatment of benign prostatic hyperplasia. Rev Urol. 2007;9(4):181–190. PMID: 18231614. Review of alpha-blocker pharmacology and comparative receptor selectivity profiles relevant to understanding silodosin’s uroselectivity.
Pharmacokinetics / Special Populations
- Katashima M, Yamamoto K, Tokuma Y, Hata T, Sawada Y, Iga T. Pharmacokinetics and disposition of silodosin (KMD-3213). Xenobiotica. 2006;36(7):603–613. doi:10.1080/00498250600692962 Primary PK reference characterising species differences, human bioavailability (~32%), protein binding (~95.6%), and dual elimination via feces (55%) and urine (34%).
- Montorsi F. Profile of silodosin. Eur Urol Suppl. 2010;9(4):491–495. doi:10.1016/j.eursup.2010.03.001 Clinical pharmacology profile summarising ADME, special populations (renal/hepatic impairment, elderly), and drug interaction data.
- Capitanio U, Brescia A, Salonia A, et al. Silodosin in the treatment of benign prostatic hyperplasia. Drug Des Devel Ther. 2010;4:291–297. doi:10.2147/DDDT.S10018 Narrative review consolidating pharmacokinetics, clinical efficacy, and safety data from both US and Japanese clinical programmes.
Medical Expulsive Therapy (Off-Label)
- Sur RL, Shore N, L’Esperance J, et al. Silodosin to facilitate passage of ureteral stones: a multi-institutional, randomized, double-blinded, placebo-controlled trial. Eur Urol. 2015;67(3):449–456. doi:10.1016/j.eururo.2014.10.021 Phase 2 multicentre RCT (n = 232) demonstrating silodosin’s benefit for distal (but not proximal/mid) ureteral stone passage compared with placebo.
- Wang H, Man LB, Huang GL, Li GZ, Wang JW. Comparative efficacy of tamsulosin versus silodosin for distal ureteral stones: a meta-analysis. PLoS One. 2018;13(8):e0203035. doi:10.1371/journal.pone.0203035 Meta-analysis of 16 studies (n = 1824) showing silodosin achieves 13% higher stone expulsion rates than tamsulosin, particularly for stones >5 mm.