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Pharmacologic class: Alpha1-adrenergic receptor antagonist

Therapeutic class: Benign prostatic hyperplasia (BPH) agent

Pregnancy risk category B


Selectively inhibits alpha1-adrenergic receptors in the lower urinary tract, relaxing smooth muscle in bladder neck and prostate


Capsules: 4 mg, 8 mg

Indications and dosages


Adults: 8 mg P.O. daily

Dosage adjustment

• Moderate renal impairment


• Severe hepatic or renal impairment

• Concomitant administration with strong CP450 3A4 (CYP3A4) inhibitors


Use cautiously in:

• moderate renal impairment

• orthostatic hypotension

• cataract surgery (risk of intraoperative floppy iris syndrome)

• concurrent use with other alpha blockers, antihypertensives, moderate CYP3A4 inhibitors, PDE5 inhibitors

• concurrent use with strong P-glycoprotein inhibitors (not recommended)

• females (not indicated)

• children (safety and efficacy not established).


• Administer drug with a meal.

Adverse reactions

CNS: dizziness, headache, insomnia, asthenia

CV: orthostatic hypotension

EENT: nasopharyngitis, nasal congestion, rhinorrhea, sinusitis

GI: diarrhea, abdominal pain

GU: retrograde ejaculation

Hematologic: purpura


Drug-drug. Antihypertensives: increased dizziness and hypotension

PDE5 inhibitors (such as tadalafil): increased risk of symptomatic hypotension

Strong CYP3A4 inhibitors (such as clarithromycin, itraconazole, ketoconazole, ritonavir, strong P-glycoprotein inhibitors (such as cyclosporine): increased silodosin plasma concentration

Drug-diagnostic tests. Prostate-specific antigen: increased level

Patient monitoring

• Monitor renal and hepatic function tests closely.

• Monitor blood pressure. Stay alert for orthostatic hypotension.

Patient teaching

• Instruct patient to take drug with a meal.

• Advise patient to move slowly when sitting up or standing, to avoid dizziness or light-headedness from sudden blood pressure decrease.

• Caution patient to avoid driving and other hazardous activities until drug's effects on concentration and alertness are known.

• Advise patient to tell ophthalmologist about taking silodosin before cataract surgery or other procedures involving the eyes, even if patient is no longer taking drug.

• As appropriate, review all other significant adverse reactions and interactions, especially those related to the drugs and tests mentioned above


(si-lo-do-sin) ,


(trade name)


Therapeutic: benign prostatic hyperplasia bph agents
Pharmacologic: alpha adrenergic blockers
Pregnancy Category: B


Treatment of the signs/symptoms or benign prostatic hyperplasia (BPH).


Blocks post synaptic alpha1-adrenergic receptors. Decreases contractions in the smooth muscle of the prostatic capsule.

Therapeutic effects

Decreased signs and symptoms of BPH (urinary urgency, hesitancy, nocturia).


Absorption: 32% absorbed following oral administration.
Distribution: Unknown.
Protein Binding: 97%.
Metabolism and Excretion: Extensively metabolized (CYP3A4, UGT2B7, and other metabolic pathways involved); 33.5% excreted in urine and 54.9% in feces.
Half-life: 13.3 hr.

Time/action profile (effect on symptoms of BPH)

POrapid24 hr24 hr*
*Following discontinuation.


Contraindicated in: HypersensitivityNot indicated for use in women or children;Severe renal impairment (CrCl less than 30 mL/min);Severe hepatic impairment (Child-Pugh score of ≥10);Concurrent use of strong CYP3A4 inhibitors or P-gp inhibitors.
Use Cautiously in: Moderate inhibitors of the CYP3A4 enzyme system;Cataract surgery (may cause intraoperative floppy iris syndrome);Moderate renal impairment (lower dose recommended); Geriatric: ↑ risk of orthostatic hypotention; Pediatric: Safety and effectiveness have not been established.

Adverse Reactions/Side Effects

Central nervous system

  • dizziness
  • headache


  • orthostatic hypotension


  • diarrhea


  • retrograde ejaculation (most frequent)


  • pruritis
  • rash
  • urticaria


  • allergic reactions


Drug-Drug interaction

Strong inhibitors of CYP3A4 (including ketoconazole, clarithromycin, itraconazole, and ritonavir ) ↓ metabolism, ↑ blood levels and risk of toxicity; concurrent use is contraindicated.Concurrent use with moderate CYP3A4 inhibitors (including diltiazem, erythromycin, and verapamil ) may ↑ levels; use cautiously.Concurrent use with antihypertensives (including calcium channel blockers and thiazides ), other alpha blockers and phosphodiesterase type 5 inhibitors (including sildenafil, tadalafil, and vardenafil )↑ the risk of dizziness and orthostatic hypotension.P-glycoprotein (P-gp) inhibitors including cyclosporine ) may ↑ levels; concurrent use not recommended.


Oral (Adults) 8 mg once daily.

Renal Impairment

Oral (Adults) CCr 30–50 mL/min—4 mg once daily.


Capsules: 4 mg, 8 mg

Nursing implications

Nursing assessment

  • Assess patient for symptoms of benign prostatic hyperplasia (urinary hesitancy, feeling of incomplete bladder emptying, interruption of urinary stream, impairment of size and force of urinary stream, terminal urinary dribbling, straining to start flow, frequency, dysuria, nocturia, urgency) before and periodically during therapy.
    • Assess patient for orthostatic reaction and syncope. Monitor BP (lying and standing) and during initial therapy and periodically thereafter.
    • Rule out prostatic carcinoma before therapy; symptoms are similar.

Potential Nursing Diagnoses

Risk for injury (Side Effects)
Noncompliance (Patient/Family Teaching)


  • Oral: Administer with food at the same meal each day.
    • If unable to swallow capsule, may open capsule and sprinkle powder inside on a tablespoonful of applesauce. Swallow immediately, within 5 min, without chewing; follow with 8 oz of cool water to ensure complete dose is swallowed. Use cool applesauce, soft enough to be swallowed without chewing. Do not store for future use or subdivide capsule contents.

Patient/Family Teaching

  • Instruct patient to take medication with the same meal each day.
    • May cause dizziness. Caution patient to avoid driving or other activities requiring alertness until response to the medication is known.
    • Caution patient to avoid sudden changes in position to decrease orthostatic hypotension, especially patients with low BP or concurrently taking antihypertensives.
    • Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and consult health care professional before taking any new medications, especially cough, cold, or allergy remedies.
    • Instruct patient to notify health care professional of medication regimen before any surgery. Patients planning cataract surgery should notify opthalmologist of silodosin therapy prior to surgery.
    • Inform patient that silodosin may cause retrograde ejaculation (orgasm with reduced or no semen). This does not pose a safety concern and is reversible with discontinuation.
    • Emphasize the importance of follow-up exams to evaluate effectiveness of medication.
    • Geriatric: Assess risk for falls; implement fall prevention program and instruct patient and family in preventing falls at home.

Evaluation/Desired Outcomes

  • Decreased symptoms of benign prostatic hyperplasia.
References in periodicals archive ?
Kissei has been aggressively promoting international development of its original products such as silodosin, mitiglinide (a diabetic medicine, brand name in Japan: Glufast(R)), etc, through outlicensing.
However, published data are limited on the use of silodosin as MET for DUS; thus we conducted a prospective randomized study to compare the efficacy and safety of silodosin vs tamsulosin as MET for single, symptomatic, uncomplicated lower ureteric stones in adults.
While no head-to-head studies have been conducted, it appears that silodosin may have a lower incidence of dizziness and orthostasis than other drugs.
Men taking certain drugs for benign prostate enlargement--such as alfuzosin (Uroxatral[R]), tamsulosin (Flomax[R]) and silodosin (Rapaflo[R])--may be at greater risk of complications during cataract surgery, so tell your surgeon if you're using one of these drugs.
M2 PHARMA-September 15, 2011-Daiichi Sankyo gains China's govt nod for silodosin for dysuria treatment(C)2011 M2 COMMUNICATIONS
Silodosin is a selective a-1 receptor (1A, 1B, 1D) antagonist with documented use in urology in the management of LUTS in BPH6 and also in spontaneous expulsion of distal ureteric stones (7).
13) Dell'Atti compared the effectiveness of silodosin and tamsulosin in the expulsion of distal ureteral stones measuring 4 to 10 mm.
Drugs known as alpha-blockers--alfuzosin (Uroxatral) silodosin (Rapaflo) or tamsulosin (Flomax)--or anticholinergic drugs like tolterodine (Detrol) or oxybutynin (Ditropan) may be used to treat urinary symptoms.
14) The selective alpha1A adrenergic receptor antagonist, silodosin, was more effective than other drugs used MET.
4] The selective alpha-blocker silodosin was recently made available in Canada and offers another option.