Alpha1 adrenergic blockers selectively block postsynaptic alpha1-adrenergic receptors, decreasing sympathetic tone on the vasculature, dilating arterioles and veins, and lowering both supine and standing BP; unlike conventional alpha adrenergic blockers (phentolamine), they do not also block alpha2 presynaptic receptors, so they do not cause reflex tachycardia. They also relax smooth muscle of bladder and prostate.

Indications

Treatment of hypertension (alone or with other drugs)

Treatment of BPH (alfuzosin, doxazosin, terazosin, tamsulosin)

Unlabeled uses: Symptomatic treatment of chronic abacterial prostatitis (terazosin)

Contraindications and cautions

Contraindicated with hypersensitivity to any alpha1-adrenergic blocker, lactation.

Use cautiously with heart failure, renal failure, pregnancy.

Adverse effects

CNS: Dizziness, headache, drowsiness, lack of energy, weakness,nervousness, vertigo, depression, paresthesias

CV: Palpitations, sodium and water re- tention, increased plasma volume, edema, dyspnea, syncope, tachycardia, orthostatic hypotension

Dermatologic: Rash, pruritus, lichen planus

EENT: Blurred vision, reddened sclera, epistaxis, tinnitus, dry mouth, nasal congestion

GI: Nausea,vomiting, diarrhea, constipation, abdominal discomfort or pain

GU: Urinary frequency, incontinence, impotence

Other: Diaphoresis

Interactions

Drug-drug

Severity and duration of hy- potension following first dose of drug may be greater in patients receiving beta-adrenergic blockers (propranolol), verapamil

Risk of severe hypotension if combined with sildenafil, tadalafil, vardenafil

Increased risk of hypotension if combined with alcohol

Nursing considerations

Assessment

History: Hypersensitivity to any alpha1- adrenergic blocker, heart failure, renal failure, lactation

Physical: Weight; skin color, lesions; orientation, affect, reflexes; ophthalmologic examination; P, BP, orthostatic BP, supine BP, perfusion, edema, auscultation; R, adventitious sounds, status of nasal mucous membranes; bowel sounds, normal output; voiding pattern, normal output; renal function tests, urinalysis

Interventions

Administer, or have patient take, first dose at night to lessen likelihood of first-dose syn- cope believed to be caused by excessive ortho- static hypotension.

Have patient lie down, and treat supportively if syncope occurs; condition is self-limiting.

Monitor patient for orthostatic hypotension: most marked in the morning, accentuated by hot weather, alcohol, exercise.

Monitor edema, weight in patients with incipient cardiac decompensation; arrange to add a thiazide diuretic to the drug regimen if sodium and fluid retention, signs of impending heart failure occur.

Provide frequent small meals, frequent mouth care if GI effects occur.

Establish safety precautions if CNS, hypotensive changes occur (side rails, accompany patient).

Arrange for analgesic for patients experiencing headache.

Teaching points

Take these drugs exactly as prescribed. Take the first dose at bedtime. Do not drive a car or operate machinery for 4 hours after the first dose.

Avoid over-the-counter drugs (nose drops, cold remedies) while taking these drugs. If you feel you need one of these preparations, consult your health care provider.

You may experience these side effects: Dizzi- ness, weakness may occur when changing position, in the early morning, after exer- cise, in hot weather, and after consuming alcohol; tolerance may occur after taking these drugs for a while, but avoid driving or engaging in tasks that require alertness while experiencing these symptoms; change position slowly, and use caution in climb- ing stairs; lie down if dizziness persists; GI upset (frequent small meals may help); dry mouth (sucking on sugarless candies, ice chips may help); stuffy nose. Most of these effects will stop with continued therapy.

Report frequent dizziness or faintness.

Representative drugs

alfuzosin doxazosin prazosin silodosin tamsulosin terazosin