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Pronunciation
(ter AY zoe sin)
Generic Available
Yes
Canadian Brand Names
Pharmacologic Category
Pharmacologic Category Synonyms
Use: Labeled Indications
Management of mild to moderate hypertension; alone or in combination with other agents such as diuretics or beta-blockers; benign prostate hyperplasia (BPH)
Use: Unlabeled/Investigational
Pediatric hypertension
Pregnancy Risk Factor
C
Lactation
Excretion in breast milk unknown
Contraindications
Hypersensitivity to quinazolines (doxazosin, prazosin, terazosin) or any component of the formulation; concurrent use with phosphodiesterase-5 (PDE-5) inhibitors including sildenafil (>25 mg), tadalafil, or vardenafil
Warnings/Precautions
Concerns related to adverse effects:
• Angina: Discontinue if symptoms of angina occur or worsen.
• Floppy iris syndrome: Intraoperative floppy iris syndrome has been observed in cataract surgery patients who were on or were previously treated with alpha1-blockers; causality has not been established and there appears to be no benefit in discontinuing alpha-blocker therapy prior to surgery.
• Orthostatic hypotension/syncope: May cause significant orthostatic hypotension and syncope, especially with first dose; anticipate a similar effect if therapy is interrupted for a few days, if dosage is rapidly increased, or if another antihypertensive drug (particularly vasodilators) or a PDE-5 inhibitor is introduced. Patients should be cautioned about performing hazardous tasks when starting new therapy or adjusting dosage upward.
Disease-related concerns:
• Hepatic impairment: Use with caution in patients with hepatic impairment.
• Prostate cancer: It is recommended to rule out prostatic carcinoma before beginning therapy.
Special populations:
• Pediatrics: Safety and efficacy have not been established in children.
Adverse Reactions
Asthenia, postural hypotension, dizziness, somnolence, nasal congestion/rhinitis, and impotence were the only events noted in clinical trials to occur at a frequency significantly greater than placebo (p <0.05).
>10%:
Central nervous system: Dizziness, headache
Neuromuscular & skeletal: Muscle weakness
1% to 10%:
Cardiovascular: Edema, palpitation, chest pain, peripheral edema (3%), orthostatic hypotension (3% to 4%), tachycardia
Central nervous system: Fatigue, nervousness, drowsiness
Gastrointestinal: Dry mouth
Genitourinary: Urinary incontinence
Ocular: Blurred vision
Respiratory: Dyspnea, nasal congestion
<1% (Limited to important or life-threatening): Sexual dysfunction, syncope (0.8%)
Postmarketing and/or case reports: Allergic reactions, anaphylaxis, atrial fibrillation, priapism, thrombocytopenia
Drug Interactions
Beta-Blockers: May enhance the orthostatic effect of Alpha1-Blockers. The risk associated with ophthalmic products is probably less than systemic products. Exceptions: Levobunolol; Metipranolol. Risk D: Consider therapy modification
Calcium Channel Blockers: Alpha1-Blockers may enhance the hypotensive effect of Calcium Channel Blockers. Risk C: Monitor therapy
Diazoxide: May enhance the hypotensive effect of Antihypertensives. Risk C: Monitor therapy
Herbs (Hypertensive Properties): May diminish the antihypertensive effect of Antihypertensives. Risk C: Monitor therapy
Herbs (Hypotensive Properties): May enhance the hypotensive effect of Antihypertensives. Risk C: Monitor therapy
Methylphenidate: May diminish the antihypertensive effect of Antihypertensives. Risk C: Monitor therapy
Phosphodiesterase 5 Inhibitors: May enhance the hypotensive effect of Alpha1-Blockers. Risk D: Consider therapy modification
Prostacyclin Analogues: May enhance the hypotensive effect of Antihypertensives. Risk C: Monitor therapy
RiTUXimab: Antihypertensives may enhance the hypotensive effect of RiTUXimab. Risk D: Consider therapy modification
Ethanol/Nutrition/Herb Interactions
Herb/Nutraceutical: Avoid dong quai if using for hypertension (has estrogenic activity). Avoid ephedra, yohimbe, ginseng (may worsen hypertension). Avoid saw palmetto. Avoid garlic (may have increased antihypertensive effect).
Mechanism of Action
Alpha1-specific blocking agent with minimal alpha2 effects; this allows peripheral postsynaptic blockade, with the resultant decrease in arterial tone, while preserving the negative feedback loop which is mediated by the peripheral presynaptic alpha2-receptors; terazosin relaxes the smooth muscle of the bladder neck, thus reducing bladder outlet obstruction
Pharmacodynamics/Kinetics
Onset of action: 1-2 hours
Absorption: Rapid
Protein binding: 90% to 95%
Metabolism: Extensively hepatic
Half-life elimination: 9.2-12 hours
Time to peak, serum: ?1 hour
Excretion: Feces (60%); urine (40%)
Dosage
Oral:
Hypertension:
Children (unlabeled use): Initial: 1 mg once daily; gradually increase dose as necessary, up to maximum of 20 mg/day
Adults: Initial: 1 mg at bedtime; slowly increase dose to achieve desired blood pressure, up to 20 mg/day; usual dose range (JNC 7): 1-20 mg once daily
Dosage reduction may be needed when adding a diuretic or other antihypertensive agent; if drug is discontinued for greater than several days, consider beginning with initial dose and retitrate as needed; dosage may be given on a twice daily regimen if response is diminished at 24 hours and hypotensive is observed at 2-4 hours following a dose
Benign prostatic hyperplasia: Adults: Initial: 1 mg at bedtime, increasing as needed; most patients require 10 mg day; if no response after 4-6 weeks of 10 mg/day, may increase to 20 mg/day
Monitoring Parameters
Standing and sitting/supine blood pressure, especially following the initial dose at 2-4 hours following the dose and thereafter at the trough point to ensure adequate control throughout the dosing interval; urinary symptoms
Dietary Considerations
May be taken without regard to meals at the same time each day.
Patient Education
Do not take any new medication during therapy unless approved by prescriber. Take as directed; at bedtime. Do not skip dose or discontinue without consulting prescriber. Follow recommended diet and exercise program. May cause drowsiness, dizziness, or impaired judgment (use caution when driving or engaging in tasks that require alertness until response to drug is known); postural hypotension (use caution when rising from sitting or lying position or when climbing stairs); dry mouth or nausea (frequent mouth care or sucking lozenges may help); urinary incontinence (void before taking medication); or sexual dysfunction (reversible, may resolve with continued use). Report altered CNS status (eg, fatigue, lethargy, confusion, nervousness); sudden weight gain (weigh yourself in the same clothes at the same time of day once a week); unusual or persistent swelling of ankles, feet, or extremities; palpitations or rapid heartbeat; respiratory difficulty; muscle weakness; or other persistent side effects. Pregnancy/breast-feeding precautions: Inform prescriber if you are or intend to become pregnant. Consult prescriber if breast-feeding.
Geriatric Considerations
Adverse reactions such as dry mouth and urinary problems can be particularly bothersome in the elderly.
Cardiovascular Considerations
An alpha1-blocker may be used in combination with other agents for the treatment of hypertension or alone in select patients who fail to respond or have contraindications to other agents. Patients with BPH may derive an extra benefit from therapy. Recently, the doxazosin treatment arm of ALLHAT (Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial) was prematurely stopped due to a significantly higher incidence (25%) of cardiovascular events (particularly heart failure events), compared to the diuretic (chlorthalidone) treatment arm. This unfavorable difference was also present when doxazosin was compared to the amlodipine and lisinopril treatment arms. This study does not address cardiovascular outcomes when doxazosin is combined with other antihypertensive medications. Consideration should be given to the ALLHAT results when considering the use of an alpha1-blocker for treatment of hypertension.
Dental Health: Effects on Dental Treatment
Key adverse event(s) related to dental treatment: Xerostomia (normal salivary flow resumes upon discontinuation) and orthostatic hypotension.
Dental Health: Vasoconstrictor/Local Anesthetic Precautions
No information available to require special precautions
Mental Health: Effects on Mental Status
Dizziness is common; may cause drowsiness or nervousness; may rarely cause insomnia or depression
Mental Health: Effects on Psychiatric Treatment
None reported
Nursing: Physical Assessment/Monitoring
Assess potential for interactions with other pharmacological agents and herbal products patient may be taking (especially anything that may decrease antihypertensive response [NSAIDS, ephedra, yohimbe, ginseng] or increase hypotensive effect [beta-blockers, diuretics, ACE inhibitors]). Assess therapeutic effectiveness (blood pressure) and adverse reactions (eg, hypotension, dizziness, somnolence, impotence) at beginning of therapy and on a regular basis with long-term therapy. When discontinuing, dose should be tapered and blood pressure monitored closely. Teach patient proper use, possible side effects/appropriate interventions, and adverse symptoms to report.
Dosage Forms
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Capsule: 1 mg, 2 mg, 5 mg, 10 mg
Pricing: U.S. (www.drugstore.com)
Capsules (Terazosin HCl)
1 mg (30): $14.45
2 mg (30): $13.99
5 mg (30): $13.99
10 mg (30): $13.99
References
Chobanian AV, Bakris GL, Black HR, et al, “The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: The JNC 7 Report,” JAMA, 2003, 289(19):2560-71.
"Major Cardiovascular Events in Hypertensive Patients Randomized to Doxazosin vs Chlorthalidone: The Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT). ALLHAT Collaborative Research Group," JAMA, 2000, 283(15):1967-75.
National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents, “The Fourth Report on the Diagnosis, Evaluation, and Treatment of High Blood Pressure in Children and Adolescents,” Pediatrics, 2004, 114(2 Suppl):555-76.
International Brand Names
Lexi-Comp.com
Last full review/revision August 2008
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