Product Details

 Action Selectively blocks postsynaptic alpha-1-adrenergic receptors, resulting in dilation of arterioles and veins.

 Indications Treatment of hypertension.

 Contraindications Hypersensitivity to doxazosin, prazosin, or terazosin.

 Route/Dosage

Adults: PO Initial dose: 1 mg bid to tid. Maintenance: 6 to 20 mg/day in divided doses (max, 40 mg/day).

Children: PO 0.5 to 7 mg tid has been suggested.

 Interactions

Alcohol: Increased risk of hypotension.

Beta-blockers: Enhanced acute orthostatic hypotensive reaction after first dose of prazosin.

Verapamil: Increased serum prazosin levels and increased sensitivity to orthostatic hypotension.

 Lab Test Interferences May cause false elevation in vanillylmandelic acid.

 Adverse Reactions

CARDIOVASCULAR: Palpitations; orthostatic hypotension; hypotension; tachycardia. CNS: Depression; dizziness; nervousness; paresthesia; asthenia; drowsiness; headache. DERMATOLOGIC: Pruritus; rash; sweating; alopecia; lichen planus. EENT: Blurred vision; conjunctivitis; tinnitus; nasal congestion; epistaxis. GI: Nausea; vomiting; dry mouth; diarrhea; constipation; abdominal discomfort or pain. GU: Impotence; urinary frequency; incontinence; priapism. RESPIRATORY: Dyspnea. OTHER: Arthralgia; edema; fever.

 Precautions

Pregnancy: Category C. Lactation: Excreted in breast milk. Children: Safety and efficacy not established. Concomitant therapy: When adding a diuretic or other antihypertensive agent, reduce dosage to 1 to 2 mg tid and then retitrate. First-dose effect: May cause marked hypotension (especially orthostatic) and syncope at 30 min after first few doses, after reintroduction, with rapid increase (at least 2 mg) in dosing, or after addition of another antihypertensive. To avoid, initiate dosing with low dose (1 mg or up to 2 mg) and gradually increase after 2 wk. Lipids: May decrease total cholesterol levels and LDLs and increase HDLs.

 Administration/Storage

• Give initial dose at bedtime to avoid syncope.
• Dosage is increased slowly, usually q 2 wk, with increase given at bedtime dose.
• Give maintenance therapy in divided doses.
• Note that efficacy does not increase when dosage exceeds 20 mg/day.
• Store at room temperature in tightly-closed, light-resistant container.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies. Note current use of antihypertensives.
• Obtain baseline BP and pulse.
• Observe for possible retention of water and sodium.
• Monitor closely for first-dose effect. If syncope occurs, place patient in recumbent position and notify health care provider.
• Notify health care provider if patient complains of dizziness, palpitations, drowsiness, fatigue, tiredness, nausea, or headache.

 Patient/Family Education

• Advise patient to take medication at same time each day.
• Warn patient about possibility of syncope or orthostasis.
• Instruct patient to report the following symptoms to health care provider: dizziness, palpitations, drowsiness, fatigue, nausea, headache.
• Caution patient to avoid sudden position changes to prevent orthostatic hypotension.
• Advise patient to avoid driving or performing other tasks requiring mental alertness for 12 to 24 hr after first dose, after dosage increase, and after resuming treatment after interruption. After the 12- to 24-hr period, advise patient to use caution.
• Instruct patient not to take OTC medications (eg, nonprescription weight loss products or cough, cold, or allergy medications) without consulting health care provider.

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Copyright © 2003 Facts and Comparisons
David S. Tatro
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