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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
• 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.
CNS: dizziness, headache, insomnia, asthenia
CV: orthostatic hypotension
EENT: nasopharyngitis, nasal congestion, rhinorrhea, sinusitis
GI: diarrhea, abdominal pain
GU: retrograde ejaculation
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
• Monitor renal and hepatic function tests closely.
• Monitor blood pressure. Stay alert for orthostatic hypotension.
• 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
ClassificationTherapeutic: benign prostatic hyperplasia bph agents
Pharmacologic: alpha adrenergic blockers
Time/action profile (effect on symptoms of BPH)
|PO||rapid||24 hr||24 hr*|
Adverse Reactions/Side Effects
Central nervous system
- orthostatic hypotension
- retrograde ejaculation (most frequent)
- allergic reactions
Drug-Drug interactionStrong 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.
Renal ImpairmentOral (Adults) CCr 30–50 mL/min—4 mg once daily.
- 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 DiagnosesRisk 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.
- 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.
- Decreased symptoms of benign prostatic hyperplasia.