|
This information has been developed and provided by an independent third-party source. Merck & Co., Inc. does not endorse and is not responsible for the accuracy of the content, or for practices or
standards of non-Merck sources.
Pronunciation
(PRAZ oh sin)
Generic Available (U.S.)
Yes
Index Terms
Brand Names: U.S.
Brand Names: Canada
Pharmacologic Category
Pharmacologic Category Synonyms
Use: Labeled Indications
Treatment of hypertension
Use: Unlabeled
Post-traumatic stress disorder (PTSD) related nightmares and sleep disruption; benign prostatic hyperplasia; Raynaud's syndrome
Pregnancy Risk Factor
C
Pregnancy Considerations
Teratogenic effects were not observed in animal studies. Limited use in pregnant women has not demonstrated any fetal abnormalities or adverse effects (Dommisse, 1983).
Lactation
Enters breast milk/use caution
Contraindications
Hypersensitivity to prazosin, quinazolines (eg, doxazosin, terazosin) or any component of the formulation
Warnings/Precautions
Concerns related to adverse effects:
• Angina: Discontinue if symptoms of angina occur or worsen.
• Floppy iris syndrome: Intraoperative floppy iris syndrome (IFIS) has been observed in cataract surgery patients who were on or were previously treated with alpha1-blockers; there appears to be no benefit in discontinuing alpha1-blockers 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 (eg, sildenafil, tadalafil, vardenafil) is introduced. Patients should be cautioned about performing hazardous tasks when starting new therapy or adjusting dosage upward.
Disease-related concerns:
• Prostate cancer: Should rule out prostatic carcinoma before beginning therapy.
Adverse Reactions
>4%:
Cardiovascular: Palpitation (5%)
Central nervous system: Dizziness (10%), headache (8%), drowsiness (8%)
Endocrine & metabolic: Decreased energy (7%)
Gastrointestinal: Nausea (5%)
Neuromuscular & skeletal: Weakness (7%)
1% to 4%:
Cardiovascular: Edema, orthostatic hypotension, syncope
Central nervous system: Depression, nervousness, vertigo
Dermatologic: Rash
Gastrointestinal: Constipation, diarrhea, vomiting, xerostomia
Genitourinary: Urinary frequency
Ocular: Blurred vision, reddened sclera
Respiratory: Dyspnea, epistaxis, nasal congestion
<1% (Limited to important or life-threatening): Abdominal discomfort, alopecia, arthralgia, diaphoresis, fever, hallucinations, impotence, incontinence, lichen planus, liver function abnormalities, MI, pancreatitis, paresthesia, positive ANA titer, priapism, pruritus, tachycardia, tinnitus
Postmarketing and/or case reports: Allergic reaction, angina, bradycardia, cataplexy, cataracts (both development and disappearance have been reported), enuresis, eye pain, flushing, gynecomastia, insomnia, leukopenia, malaise, narcolepsy (worsened), pain, pigmentary mottling and serous retinopathy, systemic lupus erythematosus, urticaria, vasculitis
Reported in association with other alpha1-blockers: Intraoperative floppy iris syndrome (with cataract surgery)
Metabolism/Transport Effects
Induces P-glycoprotein
Drug Interactions
Alpha1-Blockers: May enhance the antihypertensive effect of other Alpha1-Blockers. Risk X: Avoid combination
Amifostine: Antihypertensives may enhance the hypotensive effect of Amifostine. Management: When amifostine is used at chemotherapy doses, antihypertensive medications should be withheld for 24 hours prior to amifostine administration. If antihypertensive therapy can not be withheld, amifostine should not be administered. Risk D: Consider therapy modification
Antihypertensives: May enhance the hypotensive effect of other Antihypertensives. Risk C: Monitor therapy
Beta-Blockers: May enhance the orthostatic hypotensive 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
Dabigatran Etexilate: P-glycoprotein/ABCB1 Inducers may decrease the serum concentration of Dabigatran Etexilate. Management: Avoid concurrent use of dabigatran with a p-glycoprotein inducer when possible. Closely monitor for decreased levels/effects of dabigatran if concomitantly administering a p-glycoprotein inducer, particularly strong inducers. Risk X: Avoid combination
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
Hypotensive Agents: May enhance the adverse/toxic effect of other Hypotensive Agents. Risk C: Monitor therapy
Linagliptin: P-glycoprotein/ABCB1 Inducers may decrease the serum concentration of Linagliptin. Management: Strongly consider using an alternative to any strong P-glycoprotein inducer in patients who are being treated with linagliptin. If this combination is used, monitor patients closely for evidence of reduced linagliptin effectiveness. Risk D: Consider therapy modification
MAO Inhibitors: May enhance the orthostatic hypotensive effect of Orthostatic Hypotension Producing Agents. Risk C: Monitor therapy
Methylphenidate: May diminish the antihypertensive effect of Antihypertensives. Risk C: Monitor therapy
Pentoxifylline: May enhance the hypotensive effect of Antihypertensives. Risk C: Monitor therapy
P-glycoprotein/ABCB1 Substrates: P-glycoprotein/ABCB1 Inducers may decrease the serum concentration of P-glycoprotein/ABCB1 Substrates. P-glycoprotein inducers may also further limit the distribution of p-glycoprotein substrates to specific cells/tissues/organs where p-glycoprotein is present in large amounts (e.g., brain, T-lymphocytes, testes, etc.). Risk C: Monitor therapy
Phosphodiesterase 5 Inhibitors: May enhance the hypotensive effect of Alpha1-Blockers. Management: Ensure patient is stable on one agent prior to initiating the other, and always initiate combination using the lowest possible dose of the drug being added. When tadalafil is used for treatment of BPH, concurrent alpha 1-blockers are not recommended. 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
Yohimbine: May diminish the antihypertensive effect of Antihypertensives. Risk C: Monitor therapy
Ethanol/Nutrition/Herb Interactions
Ethanol: Avoid ethanol (may increase vasodilation).
Food: Food has variable effects on absorption.
Herb/Nutraceutical: Avoid dong quai if using for hypertension (has estrogenic activity). Avoid ephedra, yohimbe, ginseng (may worsen hypertension). Avoid saw palmetto (due to limited experience with this combination). Avoid garlic (may have increased antihypertensive effect).
Storage
Store in airtight container. Protect from light.
Mechanism of Action
Competitively inhibits postsynaptic alpha-adrenergic receptors which results in vasodilation of veins and arterioles and a decrease in total peripheral resistance and blood pressure
Pharmacodynamics/Kinetics
Onset of action: Anithypertensive: ~2 hours
Peak effect: Antihypertensive: 2-4 hours
Duration: 10-24 hours
Distribution: Hypertensive adults: Vd: 0.5 L/kg
Protein binding: 92% to 97%
Metabolism: Extensively hepatic
Bioavailability: 43% to 82%
Time to peak, plasma: ~3 hours
Half-life elimination: 2-3 hours; prolonged with congestive heart failure
Excretion: Feces, urine (6% to 10% as unchanged drug)
Dosage
Oral:
Children: Hypertension (unlabeled use): Initial: 0.05-0.1 mg/kg/day in 3 divided doses; maximum: 0.5 mg/kg/day (not to exceed 20 mg) (NHBPEP, Fourth Report)
Adults:
Hypertension: Initial: 1 mg/dose 2-3 times/day; usual maintenance dose: 2-20 mg/day in divided doses 2-3 times/day (JNC 7); maximum daily dose: 20 mg
PTSD-related nightmares and sleep disruption (unlabeled use): Initial: 1 mg at bedtime (Raskind, 2002; Raskind, 2007); titrate as tolerated to 2-15 mg at bedtime (Benedek, 2009)
Raynaud's (unlabeled use): Dosage range: 1-5 mg twice daily (Bakst, 2008)
Benign prostatic hyperplasia (unlabeled use): Initial: 0.5 mg twice daily; titrate as tolerated to 2 mg twice daily (Moran, 2001)
Elderly: Hypertension: Consider lower initial doses and titrate to response (Aronow, 2011)
Monitoring Parameters
Blood pressure, standing and sitting/supine
Test Interactions
Increased urinary VMA 17%, norepinephrine metabolite 42%; therefore, false positives may occur in screening for pheochromocytoma. If elevated VMA is found, discontinue prazosin and retest after one month.
Patient Education
Take with or without meals. Avoid alcohol. Follow recommended diet and exercise program. May cause drowsiness, dizziness, postural hypotension, headache, or nausea. Report increased nervousness or depression, sudden weight gain, palpitations or rapid heartbeat, muscle weakness, fatigue, vision changes, rash, or changes in urinary pattern.
Geriatric Considerations
Adverse effects such as orthostatic hypotension, dry mouth, and urinary problems can be particularly bothersome in the elderly.
Anesthesia and Critical Care Concerns/Other Considerations
Clinical Pearls/Comments: Alpha1 blockers do not affect renal blood flow or glomerular filtration. Orthostatic hypotension, with older alpha 1 blockers, is more of a concern.
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: Significant xerostomia (normal salivary flow resumes upon discontinuation). Significant orthostatic hypotension is a possibility; monitor patient when getting out of dental chair.
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 nightmares
Mental Health: Effects on Psychiatric Treatment
Concurrent use with low potency antipsychotics and TCAs may increase risk of postural hypotension
Nursing: Physical Assessment/Monitoring
Evaluate cardiac status and blood pressure. Monitor for orthostatic hypotension, rash, drowsiness, nausea, or vomiting prior to treatment and on a regular basis. When discontinuing, monitor blood pressure and taper dose slowly over 1 week or more.
Dosage Forms
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Capsule, oral: 1 mg, 2 mg, 5 mg
Minipress®: 1 mg, 2 mg, 5 mg
Pricing: U.S. (www.drugstore.com)
Capsules (Minipress)
1 mg (60): $55.89
2 mg (60): $75.24
5 mg (60): $133.29
Capsules (Prazosin HCl)
1 mg (60): $17.99
2 mg (60): $22.99
5 mg (60): $37.99
References
Aronow WS, Fleg JL, Pepine CJ, et al, “ACCF/AHA 2011 Expert Consensus Document on Hypertension in the Elderly: A Report of the American College of Cardiology Foundation Task Force on Clinical Expert Consensus Documents,” Circulation, 2011, 123(21):2434-506.
Bakst R, Merola JF, Franks AG Jr, et al, "Raynaud's Phenomenon: Pathogenesis and Management," J Am Acad Dermatol, 2008, 59(4):633-53.
Bandelow B, Zohar J, Hollander E, et al, “World Federation of Societies of Biological Psychiatry (WFSBP) Guidelines for the Pharmacological Treatment of Anxiety, Obsessive-Compulsive and Post-Traumatic Stress Disorders -- First Revision,” World J Biol Psychiatry, 2008, 9(4): 248-312. Available at http://www.wfsbp.org/fileadmin/pdf/guides/Guidelines_Anxiety_revision.pdf
Benedek DM, Friedman MJ, Zatzick D, et al, “Guideline Watch (March 2009): Practice Guideline for the Treatment of Patients With Acute Stress Disorder and Posttraumatic Stress Disorder.” Available at http://www.psychiatryonline.com/pracGuide/loadGuidelinePdf.aspx?file=AcuteStressDisorder-PTSD_GuidelineWatch
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.
Dommisse J, Davey DA, and Roos PJ, "Prazosin and Oxprenolol Therapy in Pregnancy Hypertension," S Afr Med J, 1983, 64(7):231-3.
"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.
Moran JA, Street PR, and Rogerson JW, "Pharmacological Management of Benign Prostatic Hypertrophy and Prostate Cancer in Older Men," Aust J Hosp Pharm, 2001, 31(2):115-9.
National High Blood Pressure Education Program (NHBPEP) 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.
Peskind ER, Bonner LT, Hoff DJ, et al, “Prazosin Reduces Trauma-Related Nightmares in Older Men With Chronic Posttraumatic Stress Disorder,” J Geriatr Psychiatry Neurol, 2003, 16(3):165-71.
Raskind MA, Dobie DJ, Kanter ED, et al, “The Alpha1-Adrenergic Antagonist Prazosin Ameliorates Combat Trauma Nightmares in Veterans With Posttraumatic Stress Disorder: A Report of 4 Cases,” J Clin Psychiatry, 2000, 61(2):129-33.
Raskind MA, Peskind ER, Kanter ED, et al, “Reduction of Nightmares and Other PTSD Symptoms in Combat Veterans by Prazosin: A Placebo-Controlled Study,” Am J Psychiatry, 2003, 160(2):371-3.
Raskind MA, Thompson C, Petrie EC, et al, “Prazosin Reduces Nightmares in Combat Veterans With Posttraumatic Stress Disorder,” J Clin Psychiatry, 2002, 63(7):565-8.
Raskind MA, Peskind ER, Hoff DJ, et al, “A Parallel Group Placebo Controlled Study of Prazosin for Trauma Nightmares and Sleep Disturbance in Combat Veterans With Post-traumatic Stress Disorder,” Biol Psychiatry, 2007, 61(8):928-34.
International Brand Names
Lexi-Comp.com
Last full review/revision January 2012
Content last modified January 2012
| 
