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INTRODUCTION

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silodosin (sil-oh-doe-sin)

Rapaflo

Classification

Therapeutic: benign prostatic hyperplasia (BPH) agents

Pharmacologic: alpha-adrenergic blockers

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Indications
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Treatment of the signs/symptoms or BPH.

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Action
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Blocks postsynaptic alpha1-adrenergic receptors. ↓ contractions in the smooth muscle of the prostatic capsule. Therapeutic Effects: ↓ signs and symptoms of BPH (urinary urgency, hesitancy, nocturia).

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Adverse Reactions/Side Effects
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CNS: dizziness, headache. CV: orthostatic hypotension. GI: diarrhea. GU: retrograde ejaculation.

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PHYSICAL THERAPY IMPLICATIONS

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Examination and Evaluation
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  • Monitor signs of BPH such as difficulty starting a urine stream, painful urination, weak urine flow, feeling that the bladder is not completely empty, frequent nighttime urination, and an urge to urinate again soon after urinating. Document any change in BPH symptoms to help assess the effects of drug therapy.

  • Assess blood pressure (BP) when patient assumes a more upright position (lying to standing, sitting to standing, lying to sitting). Document orthostatic hypotension and contact the physician when systolic BP falls >20 mm Hg, or diastolic BP falls >10 mm Hg.

  • Assess dizziness that might affect gait, balance, and other functional activities (see Appendix C). Report balance problems and functional limitations to the physician, and caution the patient and family/caregivers to guard against falls and trauma.

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Interventions
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  • Avoid physical therapy interventions that cause systemic vasodilation (large whirlpool, Hubbard tank). Additive effects of this drug and the intervention may cause a dangerous fall in blood pressure

  • To minimize orthostatic hypotension, advise patient to move slowly when assuming a more upright position.

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Patient/Client-Related Instruction
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  • Advise patient that urinary symptoms (retention, dribbling, hesitancy, urgency) should improve, and to contact the physician if these symptoms continue to worsen.

  • Instruct patient or family/caregivers to report other bothersome side effects such as severe or prolonged headache, diarrhea, or problems with ejaculation.

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Pharmacokinetics
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Absorption: 32% absorbed following oral administration.

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Distribution: Unknown.

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Protein Binding: 97%.

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Metabolism and Excretion: Extensively metabolized (CYP3A4, UGT2B7, and other metabolic pathways involved); 33.5% excreted in urine and 54.9% in feces.

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Half-life: 13.3 hr.

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Table Graphic Jump Location
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TIME/ACTION PROFILE (effect on symptoms of BPH)

ROUTE ONSET PEAK DURATION

PO

rapid

24 hr

24 hr*

*Following discontinuation.

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Contraindications/Precautions
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Contraindicated in: Not indicated for use in women or children; Severe renal impairment (CrCl <30 mL/min); Severe hepatic impairment (Child-Pugh score of 10 or greater); Concurrent use of strong CYP3A4 inhibitors or P-glycoprotein (P-gp) inhibitors.

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Use Cautiously in: Moderate inhibitors of the CYP3A4 enzyme system; Cataract surgery (may cause Intraoperative Floppy Iris Syndrome); Moderate renal impairment (lower dose recommended); Geri: Increased risk of orthostatic hypotension; Pedi: Safety and effectiveness have not been established.

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Interactions
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