Alpha-1 Selective Blockers

• blocks Alpha-1 receptors at the postsynaptic sites (vs. presynaptic sites) – so they blocks effects of both NE & E
• leads to ↓ vascular tone & vasodilation leads to ↓ BP (w/o the reflex tachy that accompanies a BP drop)
• also blocks smooth muscle receptors in the prostate, urethra, urinary bladder neck which ↑ urine flow
• most end in -zosin/-osin

Indications

• BPH ( blocks smooth muscle in prostate/urinary tract to ↑ urine flow) 
• HTN (↓ vascular tone & vasodilates)

Contraindications

• lactation

Cautions

• CHF
• renal failure
• pregnancy

Adverse Effects

• CNS: dizziness, weakness, fatigue
• CV: arrhythmia, hypotension, edema, CHF, angina
• GI: N/V, abd pain, diarrhea
• (vasodilation may cause flushing, reddened eyes, congestion, priapism/sexual dysfunction)

Kinetics

• well absorbed after oral admin
• undergo extensive hepatic metabolism and are excreted in the urine

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Drugs
1. Doxazosin (Cardura)

• Tx HTN 
• Tx BPH

Nursing Considerations for Doxazosin

• by selective competitive inhibition of alpha 1-adrenoreceptors,  produces vasodilation in both resistance (arterioles) and capacitance (veins) vessels – results in both ↓ peripheral vascular resistance & ↓ BP
• Monitor BP w/ pt lying down & standing – teach slow change of position
• Monitor BP 2–6 h after initial dose or any ↑ dose. (this is when postural hypotension is most likely to occur)
•        doses > 4mg ↑ risk postural hypotension
• Do not drive or engage in other potentially hazardous activities for 12–24 h after first dose or an ↑ dosage or when med is restarted after an interruption in dosage. 
• Report to the physician episodes of dizziness or palpitations. These will require a dosage adjustment.
• Do not breast feed while taking this drug.

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2. Terazosin (Hytrin)

• Tx HTN
• Tx BPH

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3. Prazosin (Minipress)

• Tx HTN (usually adjunct w/ another med)

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4. Tamsulosin (Flomax)

• only for BPH

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5. Alfuzosin (Uroxatral)

• only for BPH

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Drug Interactions

• ↑ hypotensive effects w/ other vasodilators or antihypertensives (nitrates, Ca blockers, ACE-I)

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Nursing Mgmt for All A&B Agonists

• When treating BPH, must first rule out prostate cancer so the drug can't mask cancer Sx
• Cardura & Terazosin can be used to treat BPH – must educate pt about antihypertensive AE
• check labs per usual (esp kidney function)
• baseline cardiac assessment
• ask pt about UO & urine flow (force of stream? full emptying? nocturia? frequency?)
•        monitor I&O if hospitalized