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Pronunciation:

(doks AY zoe sin)

U.S. Brand Names:

Cardura®

Synonyms:

Doxazosin Mesylate

Generic Available:

Yes

Canadian Brand Names:

Alti-Doxazosin; Apo-Doxazosin®; Cardura-1™; Cardura-2™; Cardura-4™; Gen-Doxazosin; Novo-Doxazosin

Use:

Treatment of hypertension alone or in conjunction with diuretics, cardiac glycosides, ACE inhibitors, or calcium antagonists (particularly appropriate for those with hypertension and other cardiovascular risk factors such as hypercholesterolemia and diabetes mellitus); treatment of urinary outflow obstruction and/or obstructive and irritative symptoms associated with benign prostatic hyperplasia (BPH), particularly useful in patients with troublesome symptoms who are unable or unwilling to undergo invasive procedures, but who require rapid symptomatic relief; can be used in combination with finasteride

Pregnancy Risk Factor:

Lactation:

Excretion in breast milk unknown

Contraindications:

Hypersensitivity to quinazolines (prazosin, terazosin), doxazosin, or any component of the formulation; concurrent use with phosphodiesterase-5 (PDE-5) inhibitors including sildenafil (>25 mg), tadalafil, or vardenafil

Warnings/Precautions:

Can cause significant orthostatic hypotension and syncope, especially with first dose. Prostate cancer should be ruled out before starting for BPH. May need dosage adjustment in severe hepatic dysfunction. Anticipate a similar effect if therapy is interrupted for a few days, if dosage is rapidly increased, or if another antihypertensive drug is introduced.

Adverse Reactions:

Note: "Combination therapy" refers to doxazosin and finasteride.

>10%:

Cardiovascular: Postural hypotension (combination therapy 18%)

Central nervous system: Dizziness (16% to 19%; combination therapy 23%), headache (10% to 14%)

Endocrine & metabolic: Impotence (combination therapy 23%), libido decreased (combination therapy 12%)

Genitourinary: Ejaculation disturbances (combination therapy 14%)

Neuromuscular & skeletal: Weakness (combination therapy 17%)

1% to 10%:

Cardiovascular: Orthostatic hypotension (dose related; 0.3% up to 10%), edema (3% to 4%), hypotension (2%), palpitation (1% to 2%), chest pain (1% to 2%), arrhythmia (1%), syncope (2%), flushing (1%)

Central nervous system: Fatigue (8% to 12%), somnolence (3% to 5%), nervousness (2%), pain (2%), vertigo (2%), insomnia (1%), anxiety (1%), paresthesia (1%), movement disorder (1%), ataxia (1%), hypertonia (1%), depression (1%), weakness (1%)

Dermatologic: Rash (1%), pruritus (1%)

Endocrine & metabolic: Sexual dysfunction (2%)

Gastrointestinal: Abdominal pain (2%), diarrhea (2%), dyspepsia (1% to 2%), nausea (2% to 3%), xerostomia (1% to 2%), constipation (1%), flatulence (1%)

Genitourinary: Urinary tract infection (1%), impotence (1%), polyuria (2%), incontinence (1%)

Neuromuscular & skeletal: Back pain (2%), arthritis (1%), muscle weakness (1%), myalgia (1%), muscle cramps (1%)

Ocular: Abnormal vision (1% to 2%), conjunctivitis (1%)

Otic: Tinnitus (1%)

Respiratory: Rhinitis (3%), dyspnea (1% to 3%), respiratory disorder (1%), epistaxis (1%)

Miscellaneous: Diaphoresis increased (1%), flu-like syndrome (1%)

<1% (Limited to important or life-threatening): Abnormal lacrimation, abnormal thinking, agitation, alopecia, amnesia, angina, anorexia, appetite, bradycardia, breast pain, bronchospasm, confusion, cough, depersonalization, dry skin, earache, eczema, emotional lability, fecal incontinence, fever, gastroenteritis, gout, hot flashes, hypoesthesia, hypokalemia, impaired concentration, infection, lymphadenopathy, migraine, MI, pallor, paranoia, paresis, parosmia, peripheral ischemia, pharyngitis, photophobia, purpura, renal calculus, rigors sinusitis, stroke, syncope, tachycardia, taste perversion, thirst, twitching, weight gain/loss,

Postmarketing and/or case reports: Allergic reaction, bradycardia, bronchospasm, cataplexy, cholestasis, enuresis, gynecomastia, hematuria, hepatitis, leukopenia, micturition abnormality, nocturia, priapism, systemic lupus erythematosus, thrombocytopenia, urticaria, vomiting

Overdosage/Toxicology:

Symptoms of overdose include severe hypotension, drowsiness, and tachycardia. Treatment is supportive and symptomatic.

Drug Interactions:

ACE inhibitors: Hypotensive effect may be increased.

Beta-blockers: Hypotensive effect may be increased.

Calcium channel blockers: Hypotensive effect may be increased.

NSAIDs may reduce antihypertensive efficacy.

Sildenafil, tadalafil, vardenafil: Blood pressure-lowering effects are additive. Use of tadalafil or vardenafil is contraindicated by the manufacturer. Use sildenafil with extreme caution (dose 25 mg).

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 when used for BPH (due to limited experience with this combination). Avoid garlic (may have increased antihypertensive effect).

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; approximately 50% as potent on a weight by weight basis as prazosin

Pharmacodynamics/Kinetics:

Not significantly affected by increased age

Duration: >24 hours

Metabolism: Extensively hepatic

Half-life elimination: 22 hours

Time to peak, serum: 2-3 hours

Excretion: Feces (63%); urine (9%)

Dosage:

Oral:

Adults: 1 mg once daily in morning or evening; may be increased to 2 mg once daily. Thereafter titrate upwards, if needed, over several weeks, balancing therapeutic benefit with doxazosin-induced postural hypotension

Hypertension: Maximum dose: 16 mg/day

BPH: Goal: 4-8 mg/day; maximum dose: 8 mg/day

Elderly: Initial: 0.5 mg once daily

Administration:

Syncope may occur usually within 90 minutes of the initial dose.

Monitoring Parameters:

Blood pressure, standing and sitting/supine

Test Interactions:

Increased urinary VMA 17%, norepinephrine metabolite 42%

Patient Education:

Inform prescriber of all prescriptions, OTC medications, or herbal products you are taking, and any allergies you have. 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); or dry mouth or nausea (frequent mouth care or sucking lozenges may help). Report increased nervousness or depression; 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; muscle weakness, fatigue, or pain; or other persistent side effects. Pregnancy/breast-feeding precautions: Inform prescriber if you are or intend to become pregnant. Consult prescriber if breast-feeding.

Additional Information:

First-dose hypotension occurs less frequently with doxazosin as compared to prazosin; this may be due to its slower onset of action.

Cardiovascular Considerations:

Doxazosin 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.

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.

Mental Health: Effects on Psychiatric Treatment:

Psychotropics may potentiate the hypotensive effects of doxazosin

Dosage Forms:

Tablet: 1 mg, 2 mg, 4 mg, 8 mg

International Brand Names:

Adco-Doxazosin® (ZA); Alfadil® BPH (SE); Alfadil® (SE); Alfamedin® (DE); Alphapres® (YU); Alti-Doxazosin (CA); Angicon® (CL); Apo-Doxazosin® (CA); Ascalan® (AT); Benur® (IT); Cardenalin® (JP); Cardoral® (IL); Cardosin® (DK); Cardoxan® (NZ); Cardugen® (ZA); Cardular® (DE); Cardura-1™ (CA); Cardura-2™ (CA); Cardura-4™ (CA); Cardura® (AR, CH, CL, CZ, GB, HK, HU, ID, IE, IT, MX, NL, PL, RO, RU, SG, SI, TH, TR, YU, ZA); Carduran® (BR, CO, DK, ES, NO); Carduran Neo® (ES); Cardura XL® (GB, HU, PL, RO); Dedralen® (IT); Diblocin® (DE); Doksura® (TR); Dorbantil® (CL); Dosan (NZ); Doxacard® (IN); Doxacar® (DK); Doxacor® (DE); Doxagamma® (DE); Doxaloc® (IL); Doxamax® (DE); Doxanorm® (PL); Doxapress® (AT); Doxa-Puren® (DE); Doxaratio® (PL); Doxar® (PL); Doxasin® (AR); Doxatan® (IE); Doxatensa® (ES); DoxaUro® (DE); Doxazoflo® (DE); Doxazomerck® (DE); Doxazosina Alter® (ES); Doxazosina Cinfa® (ES); Doxazosina Combino Pharm® (ES); Doxazosina Geminis® (ES); Doxazosin AL® (DE); Doxazosina Normon® (ES); Doxazosina Pharmagenus® (ES); Doxazosin Apogepha® (DE); Doxazosina Ratiopharm® (ES); Doxazosin Arcana® (AT); Doxazosin Arrow® (DK); Doxazosina Ur® (ES); Doxazosin AZU® (DE); Doxazosin beta® (DE); Doxazosin dura® (DE); Doxazosin findusFit® (DE); Doxazosin® (GB, NO); Doxazosin Genericon® (AT); Doxazosin Heumann® (DE); Doxazosin Klast® (DE); Doxazosin Pliva® (DK); Doxazosin Ratiopharm® (AT, DE); Doxazosin Sandoz® (DE); Doxazosin Stada® (DE); Doxazosin Uro Hexal® (DE); Doxazosin von ct® (DE); Doxazosin-Wolff® (DE); Doxolbran® (AR, DO); Dozasin® (RO); Gen-Doxazosin (CA); Hibadren® (AT); HPB® (DO); Jutalar® (DE); Kaltensif® (ID); Kamiren® (CZ, PL, RO, SI); Maguran® (GR); Magurol® (RO); Mesilato de Doxazosina® (BR); MTW-Doxazosin® (DE); Novo-Doxazosin (CA); Pencor® (TH); Prodil® (BR); Progandol Neo® (ES); Prostadilat® (AT); Prostatic® (PL); Prostazosina® (AR); Supressin® (AT); Tonocardin® (HR, RU, SI); Unoprost® (BR); Uriduct® (DE); Zoflux® (BR); Zoxan® (FR); Zoxon® (PL, RO)

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.

Davis BR, Cutler JA, Gordon DJ, et al, "Rationale and Design for the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT). ALLHAT Research Group,"Am J Hypertens, 1996, 9(4 Pt 1):342-60.

"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.

McConnell JD, Roehrborn CG, Bautista OM, et al, "The Long-Term Effect of Doxazosin, Finasteride, and Combination Therapy on the Clinical Progression of Benign Prostatic Hyperplasia. Medical Therapy of Prostatic Symptoms (MTOPS) Research Group,"N Engl J Med, 2003, 349(25):2387-98.

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