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Terazosin

Pronunciation

Pronunciation: ter-AZE-oh-sin
Class: Alpha-1-adrenergic blocker

Trade Names

Hytrin
- Capsules 1 mg
- Capsules 2 mg
- Capsules 5 mg
- Capsules 10 mg

Apo-Terazosin (Canada)
Novo-Terazosin (Canada)
PMS-Terazosin (Canada)
ratio-Terazosin (Canada)

Pharmacology

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

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Pharmacokinetics

Absorption

Oral terazosin is completely absorbed. Food delayed the time to peak concentration by 1 h. T max occurs 1 h after dosing.

Distribution

Terazosin is 90% to 94% bound to plasma proteins.

Metabolism

Terazosin undergoes minimal first-pass metabolism.

Elimination

Terazosin t ½ is approximately 12 h. Approximately 40% of an orally administered dose is excreted in urine and approximately 60% is excreted in feces.

Special Populations

Elderly

After oral administration, plasma Cl was decreased 31.7% in patients older than 70 yr of age vs patients 20 to 39 yr of age.

Indications and Usage

Management of hypertension and symptomatic benign prostatic hyperplasia (BPH).

Contraindications

Hypersensitivity to doxazosin or prazosin.

Dosage and Administration

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 to 5 mg every day; may consider twice daily dosing (max, 20 mg/day).

BPH
Adults

PO .

Initial

1 mg at bedtime. (Do not exceed this as initial dose); increase dose in step-wise fashion.

Usual maintenance

10 mg every day for minimum of 4 to 6 wk (max, 20 mg/day).

Storage/Stability

Store in tight container in cool location.

Drug Interactions

None well documented.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Palpitations; orthostatic hypotension; hypotension; tachycardia; arrhythmias; vasodilation.

CNS

Dizziness; nervousness; paresthesia; somnolence; anxiety; headache; insomnia; weakness; drowsiness.

Dermatologic

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.

Genitourinary

Impotence; urinary frequency; UTI.

Respiratory

Dyspnea; bronchitis; bronchospasm; flu symptoms; increased cough.

Miscellaneous

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 to 90 min after first few doses, after reintroduction, with rapid increase in dosing, or after addition of another antihypertensive; to avoid, initiate dosing with low dose and gradually increase after 2 wk; monitor patients carefully.

Hemodilution

Small decreases in hematocrit, hemoglobin, WBCs, total protein, and albumin may occur, possibly because of hemodilution.

Overdosage

Symptoms

Severe hypotension.

Patient Information

  • 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 h after initial dose.
  • Advise patient to follow up with health care provider to monitor BP.
  • Caution patient to rise slowly from lying or sitting position to minimize dizziness.
  • Instruct patient to report these symptoms to health care provider: dizziness, visual changes, palpitations.
  • Alert male patients that impotence may be an adverse reaction.
  • Explain potential adverse reactions: arthralgia, weight gain, tinnitus, pruritus, epistaxis, blurred vision. Be certain patient understands that health care provider should be made aware of any significant adverse reactions.
  • Caution patient to avoid sudden position changes to prevent orthostatic hypotension.

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