Terazosin

A to Z Drug Facts

 Action Selectively blocks post-synaptic alpha₁-adrenergic receptors, resulting in dilation of arterioles and veins.

 Indications Management of hypertension and symptomatic benign prostatic hyperplasia.

 Contraindications Hypersensitivity to doxazosin or prazosin.

 Route/Dosage

Hypertension

ADULTS: PO Initial: 1 mg at bedtime. (Do not exceed this as initial dose to avoid severe hypotensive effects; reinstitute at this dose if drug is discontinued for several days). Maintenance: 1–5 mg q day; may consider bid dosing (maximum 20 mg/day).

Benign Prostatic Hyperplasia

ADULTS: PO Initial: 1 mg at bedtime. (Do not exceed this as initial dose); increase dose in stepwise fashion. Usual maintenance: 10 mg q day for minimum of 4–6 wk (maximum 20 mg/day).

 Interactions None well documented.

 Lab Test Interferences None well documented.

 Adverse Reactions

CV: Palpitations; orthostatic hypotension; hypotension; tachycardia; arrhythmias; vasodilation. CNS: Dizziness; nervousness; paresthesia; somnolence; anxiety; headache; insomnia; weakness; drowsiness. DERM: Pruritus; rash; sweating. EENT: Blurred or abnormal vision; conjunctivitis; tinnitus; nasal congestion; sinusitis; epistaxis; pharyngitis. GI: Nausea; vomiting; dry mouth; diarrhea; constipation; abdominal discomfort or pain; flatulence. GU: Impotence; urinary frequency; urinary tract infection. RESP: Dyspnea; bronchitis; bronchospasm; flu symptoms; increased cough. OTHER: Shoulder; neck; back or extremity pain; arthralgia; edema; fever; weight gain.

 Precautions

Pregnancy: Category C. Lactation: Undetermined. Children: Safety and efficacy not established. BPH complications: Long-term effects on incidence of surgery, acute urinary obstruction or other complications of BPH have not been determined. First-dose effect: May cause marked hypotension (especially orthostatic) and syncope at 15–90 min after first few doses, after reintroduction, with rapid increase in dosing, or after addition of another anti-hypertensive; to avoid, initiate dosing with low dose and gradually increase after 2 weeks; monitor patients carefully. Hemodilution: Small decreases in hematocrit, hemoglobin, WBCs, total protein and albumin may occur, possibly because of hemodilution.

 Administration/Storage

• Give orally. Maximum dosage should not exceed 20 mg.
• For benign prostatic hypertrophy, increase dose in stepwise fashion, as prescribed.
• Store in tight container in cool location.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies.
• Assess BP response and pulse after administration to aid dosage adjustment.
• Check weight daily.
• Monitor I&O.
• Implement safety precautions for patients who experience dizziness. Fainting occasionally occurs after the first dose.
• Observe for symptoms of decreased blood pressure, such as dizziness.
• Assess for potential respiratory side effects, including dyspnea, bronchospasm or cough.

 Patient/Family Education

• Explain to patient that first few doses may cause hypotension and syncope. Therefore, initially, terazosin should be taken at bedtime and patient should be warned to stay prone after taking dose. After first few doses, orthostatic hypotension with syncope is rare.
• Advise patient to avoid otc cough, cold, and allergy medicines containing sympathomimetics, and identify common examples.
• Instruct patient to avoid driving or other activities that require alertness for first 24 hours after initial dose.
• Advise patient to follow up with physician to monitor BP.
• Caution patient to rise slowly from lying or sitting position to minimize dizziness.
• Instruct patient to report these symptoms to physician: dizziness, visual changes or palpitations.
• Alert male patients that impotence may be side effect.
• Explain potential adverse reactions: arthralgia, weight gain, tinnitus, pruritus, epistaxis, and blurred vision. Be certain patient understands that physician should be made aware of any significant adverse reactions.
• Caution patient to avoid sudden position changes to prevent orthostatic hypotension.

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Copyright © 2003 Facts and Comparisons
David S. Tatro
A to Z Drug Facts