Medical term:

silo

silodosin

Rapaflo

Pharmacologic class: Alpha₁-adrenergic receptor antagonist

Therapeutic class: Benign prostatic hyperplasia (BPH) agent

Pregnancy risk category B

Action

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

Availability

Capsules: 4 mg, 8 mg

Indications and dosages

➣ BPH

Adults: 8 mg P.O. daily

Dosage adjustment

• Moderate renal impairment

Contraindications

• Severe hepatic or renal impairment

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

Precautions

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).

Administration

• 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

Interactions

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

silodosin

(si-lo-do-sin) ,

Rapaflo

(trade name)

Classification

Therapeutic: benign prostatic hyperplasia bph agents
Pharmacologic: alpha adrenergic blockers

Pregnancy Category: B

Indications

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

Action

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).

Pharmacokinetics

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)

ROUTE	ONSET	PEAK	DURATION
PO	rapid	24 hr	24 hr*

*Following discontinuation.

Contraindications/Precautions

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

Cardiovascular

orthostatic hypotension

Gastrointestinal

diarrhea

Genitourinary

retrograde ejaculation (most frequent)

Dermatologic

pruritis
rash
urticaria

Miscellaneous

allergic reactions

Interactions

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.

Route/Dosage

Oral (Adults) 8 mg once daily.

Renal Impairment

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

Availability

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)

Implementation

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.

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