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Here’s what to ask a doctor about hereditary angioedema

Doxazosin

Pronunciation

Pronunciation

(doks AY zoe sin)

Index Terms

  • Doxazosin Mesylate

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Tablet, Oral:

Cardura: 1 mg, 2 mg, 4 mg, 8 mg [scored]

Generic: 1 mg, 2 mg, 4 mg, 8 mg

Tablet Extended Release 24 Hour, Oral:

Cardura XL: 4 mg, 8 mg

Brand Names: U.S.

  • Cardura
  • Cardura XL

Pharmacologic Category

  • Alpha1 Blocker
  • Antihypertensive

Pharmacology

Hypertension: Competitively inhibits postsynaptic alpha1-adrenergic receptors which results in vasodilation of veins and arterioles and a decrease in total peripheral resistance and blood pressure; ~50% as potent on a weight by weight basis as prazosin.

BPH: Competitively inhibits postsynaptic alpha1-adrenergic receptors in prostatic stromal and bladder neck tissues. This reduces the sympathetic tone-induced urethral stricture causing BPH symptoms.

Metabolism

Extensively hepatic to active metabolites; primarily via CYP3A4; secondary pathways involve CYP2D6 and 2C9

Excretion

Feces (~63%, primarily as metabolites [4.8% as unchanged]); urine (9%, primarily as metabolites)

Time to Peak

Serum: Immediate release: 2 to 3 hours; Extended release: 8 ± 3.7 to 9 ± 4.7 hours

Duration of Action

>24 hours

Half-Life Elimination

Immediate release: ~22 hours; Extended release: 15 to 19 hours

Protein Binding

~98%

Special Populations: Hepatic Function Impairment

Immediate release: 40% increase in exposure in mild impairment (Child-Pugh class A).

Special Populations: Elderly

Extended release: Cmax and AUC increased 27% and 34% respectively in elderly patients.

Use: Labeled Indications

Benign prostatic hyperplasia: Treatment of signs and symptoms of benign prostatic hyperplasia (BPH).

Hypertension (immediate release only): Management of hypertension (monotherapy or in combination with other antihypertensives).

Note: The 2014 guideline for the management of high blood pressure in adults (Eighth Joint National Committee [JNC 8]) does not recommend the use of doxazosin in the treatment of hypertension (JNC8 [James 2013]). According to the AHA/ACC/ASH 2015 scientific statement for the treatment of hypertension in patients with coronary artery disease (CAD), doxazosin should only be used if other drugs for the management of hypertension and heart failure do not achieve BP control at maximum tolerated doses (AHA/ACC/ASH [Rosendorff 2015]).

Use: Unlabeled

Pediatric hypertension; facilitation of distal ureteral stone expulsion; erectile dysfunction in patients with concomitant BPH

Contraindications

Hypersensitivity to doxazosin, other quinazolines (eg, prazosin, terazosin), or any component of the formulation.

Dosing: Adult

BPH: Oral:

Immediate release: Initial: 1 mg once daily; may titrate (by doubling the daily dose [eg, to 2 mg, then 4 mg, then 8 mg]) at 1- to 2-week intervals up to 8 mg once daily based on patient response and tolerability (maximum: 8 mg/day).

Reinitiation of therapy: If therapy is discontinued for several days, restart at 1 mg dose and titrate using initial dosing regimen.

Extended release: 4 mg once daily; may titrate based on response and tolerability every 3 to 4 weeks to 8 mg once daily (maximum: 8 mg/day).

Reinitiation of therapy: If therapy is discontinued for several days, restart at 4 mg dose and titrate using initial dosing regimen.

Note: Conversion to extended release from immediate release: Omit final evening dose of immediate release prior to starting morning dosing with extended release product; initiate extended release product using 4 mg once daily.

Hypertension: Oral: Immediate release: Initial: 1 mg once daily; may titrate by doubling the daily dosage up to 16 mg once daily based on blood pressure response; usual dosage range (ASH/ISH [Weber 2014]): 1 to 2 mg once daily; Maximum: 16 mg/day.

Reinitiation of therapy: If therapy is discontinued for several days, restart at 1 mg dose and titrate using initial dosing regimen.

Ureteral calculi (distal) expulsion (off-label use): Oral: Immediate release: 4 mg once daily in evening (Gurbuz 2011; Resorlu 2011). Note: Patients with stones >10 mm were excluded from studies.

Dosing: Geriatric

Refer to adult dosing. In the management of hypertension, consider lower initial doses (eg, immediate release: 0.5 mg once daily) and titrate to response (Aronow 2011)

Dosing: Pediatric

Hypertension (off-label use): Children and Adolescents 1 to 17 years: Oral: Immediate release: Initial: 1 mg once daily; maximum: 4 mg/day (NHBPEP 2004)

Dosing: Renal Impairment

There are no dosage adjustments provided in the manufacturer’s labeling (however, limited data suggest renal impairment does not significantly alter pharmacokinetic parameters).

Dosing: Hepatic Impairment

Mild to moderate impairment (Child-Pugh class A or B): There are no dosage adjustments provided in the manufacturer’s labeling; use with caution.

Severe impairment (Child-Pugh class C): Use is not recommended.

Administration

Extended release: Swallow tablets whole; do not crush, cut, chew, or divide. Administer with morning meal.

Immediate release: Administer daily dose either in the morning or evening.

Dietary Considerations

Administer extended-release tablet with morning meal.

Storage

Store at 25°C (77°F); excursions permitted between 15°C to 30°C (59°F to 86°F).

Drug Interactions

Alpha-/Beta-Agonists: Alpha1-Blockers may diminish the vasoconstricting effect of Alpha-/Beta-Agonists. Similarly, Alpha-/Beta-Agonists may antagonize Alpha1-Blocker vasodilation. Monitor therapy

Alpha1-Agonists: Alpha1-Blockers may diminish the vasoconstricting effect of Alpha1-Agonists. Similarly, Alpha1-Agonists may antagonize Alpha1-Blocker vasodilation. Monitor therapy

Alpha1-Blockers: May enhance the antihypertensive effect of other Alpha1-Blockers. Avoid combination

Amifostine: Blood Pressure Lowering Agents may enhance the hypotensive effect of Amifostine. Management: When amifostine is used at chemotherapy doses, blood pressure lowering medications should be withheld for 24 hours prior to amifostine administration. If blood pressure lowering therapy cannot be withheld, amifostine should not be administered. Consider therapy modification

Amphetamines: May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy

Antipsychotic Agents (Second Generation [Atypical]): Blood Pressure Lowering Agents may enhance the hypotensive effect of Antipsychotic Agents (Second Generation [Atypical]). Monitor therapy

Aprepitant: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Barbiturates: May enhance the hypotensive effect of Blood Pressure Lowering Agents. 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. Monitor therapy

Boceprevir: May increase the serum concentration of Doxazosin. Avoid combination

Bosentan: May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

Brimonidine (Topical): May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Calcium Channel Blockers: Alpha1-Blockers may enhance the hypotensive effect of Calcium Channel Blockers. Monitor therapy

Conivaptan: May increase the serum concentration of CYP3A4 Substrates. Avoid combination

CYP3A4 Inducers (Moderate): May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

CYP3A4 Inducers (Strong): May increase the metabolism of CYP3A4 Substrates. Management: Consider an alternative for one of the interacting drugs. Some combinations may be specifically contraindicated. Consult appropriate manufacturer labeling. Consider therapy modification

CYP3A4 Inhibitors (Moderate): May decrease the metabolism of CYP3A4 Substrates. Monitor therapy

CYP3A4 Inhibitors (Strong): May decrease the metabolism of CYP3A4 Substrates. Consider therapy modification

Dabrafenib: May decrease the serum concentration of CYP3A4 Substrates. Management: Seek alternatives to the CYP3A4 substrate when possible. If concomitant therapy cannot be avoided, monitor clinical effects of the substrate closely (particularly therapeutic effects). Consider therapy modification

Dapoxetine: May enhance the orthostatic hypotensive effect of Alpha1-Blockers. Monitor therapy

Dasatinib: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Deferasirox: May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

Diazoxide: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

DULoxetine: Blood Pressure Lowering Agents may enhance the hypotensive effect of DULoxetine. Monitor therapy

Enzalutamide: May decrease the serum concentration of CYP3A4 Substrates. Management: Concurrent use of enzalutamide with CYP3A4 substrates that have a narrow therapeutic index should be avoided. Use of enzalutamide and any other CYP3A4 substrate should be performed with caution and close monitoring. Consider therapy modification

Fosaprepitant: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Fusidic Acid (Systemic): May increase the serum concentration of CYP3A4 Substrates. Avoid combination

Herbs (Hypertensive Properties): May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy

Herbs (Hypotensive Properties): May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Hypotension-Associated Agents: Blood Pressure Lowering Agents may enhance the hypotensive effect of Hypotension-Associated Agents. Monitor therapy

Idelalisib: May increase the serum concentration of CYP3A4 Substrates. Avoid combination

Ivacaftor: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Levodopa: Blood Pressure Lowering Agents may enhance the hypotensive effect of Levodopa. Monitor therapy

Luliconazole: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Methylphenidate: May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy

MiFEPRIStone: May increase the serum concentration of CYP3A4 Substrates. Management: Minimize doses of CYP3A4 substrates, and monitor for increased concentrations/toxicity, during and 2 weeks following treatment with mifepristone. Avoid cyclosporine, dihydroergotamine, ergotamine, fentanyl, pimozide, quinidine, sirolimus, and tacrolimus. Consider therapy modification

Mitotane: May decrease the serum concentration of CYP3A4 Substrates. Management: Doses of CYP3A4 substrates may need to be adjusted substantially when used in patients being treated with mitotane. Consider therapy modification

Molsidomine: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Netupitant: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Nicorandil: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Nitroprusside: Blood Pressure Lowering Agents may enhance the hypotensive effect of Nitroprusside. Monitor therapy

Obinutuzumab: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Management: Consider temporarily withholding blood pressure lowering medications beginning 12 hours prior to obinutuzumab infusion and continuing until 1 hour after the end of the infusion. Consider therapy modification

Palbociclib: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Pentoxifylline: May enhance the hypotensive effect of Blood Pressure Lowering Agents. 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. Consider therapy modification

Prostacyclin Analogues: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Quinagolide: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Siltuximab: May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

Simeprevir: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

St John's Wort: May decrease the serum concentration of CYP3A4 Substrates. Management: Consider an alternative for one of the interacting drugs. Some combinations may be specifically contraindicated. Consult appropriate manufacturer labeling. Consider therapy modification

Stiripentol: May increase the serum concentration of CYP3A4 Substrates. Management: Use of stiripentol with CYP3A4 substrates that are considered to have a narrow therapeutic index should be avoided due to the increased risk for adverse effects and toxicity. Any CYP3A4 substrate used with stiripentol requires closer monitoring. Consider therapy modification

Tocilizumab: May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

Yohimbine: May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy

Adverse Reactions

>10%: Central nervous system: Dizziness (5% to 19%), malaise (≤12%), fatigue (8% to ≤12%), headache (6% to 10%)

1% to 10%:

Cardiovascular: Edema (3% to 4%), hypotension (1% to 2%), orthostatic hypotension (<1% to 2%), cardiac arrhythmia (1%), facial edema (1%), flushing (1%), palpitations (1%)

Central nervous system: Drowsiness (1% to 5%), vertigo (2% to 4%), pain (2%), anxiety (1%), ataxia (1%), hypertonia (1%), insomnia (1%), movement disorder (1%), myasthenia (1%)

Endocrine & metabolic: Sexual disorder (2%)

Gastrointestinal: Abdominal pain (2%), nausea (1% to 2%), dyspepsia (1%), xerostomia (1%)

Genitourinary: Urinary incontinence (1%), urinary tract infection (1%)

Neuromuscular & skeletal: Weakness (4% to 7%), muscle cramps (1%), myalgia (1%), arthralgia (≤1%), arthritis (≤1%)

Ophthalmic: Visual disturbance (2%)

Otic: Tinnitus (1%)

Renal: Polyuria (2%)

Respiratory: Respiratory tract infection (5%), rhinitis (3%), dyspnea (1% to 3%), epistaxis (1%)

<1% (Limited to important or life-threatening): Abnormal hepatic function tests, abnormal lacrimation, abnormality in thinking, agitation, alopecia, altered sense of smell, amnesia, angina pectoris, anorexia, blurred vision, bradycardia, bronchospasm (aggravated), cerebrovascular accident, cholestasis, cholestatic hepatitis, confusion, decreased libido, depersonalization, dysgeusia, dysuria, emotional lability, fecal incontinence, flu-like symptoms, gastroenteritis, gastrointestinal obstruction, gout, gynecomastia, hematuria, hepatitis, hot flash, hypersensitivity reaction, hypoesthesia, hypokalemia, impotence, increased appetite, increased thirst, infection, intraoperative floppy iris syndrome (cataract surgery), lack of concentration, leukopenia, lymphadenopathy, mastalgia, migraine, myocardial infarction, nephrolithiasis, nervousness, neutropenia, nocturia, orthostatic dizziness, otalgia, paranoia, paresis, paresthesia, peripheral ischemia, photophobia, priapism, purpura, rigors, syncope, tachycardia, thrombocytopenia, tremor, twitching, urinary frequency, urination disorder, xeroderma

Warnings/Precautions

Concerns related to adverse effects:

• Allergic reactions: May occur, including skin rash, urticaria, pruritus, angioedema, and respiratory symptoms.

• CNS depression: May cause CNS depression, which may impair physical or mental abilities; patients must be cautioned about performing tasks that require mental alertness (eg, operating machinery or driving).

• Floppy iris syndrome: Intraoperative floppy iris syndrome 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 alpha-blocker therapy prior to surgery. May require modifications to surgical technique.

• Hematologic effect: Decreases in white blood cells (WBC) and neutrophil count have been reported; WBC and neutrophils returned to normal after discontinuation.

• Orthostatic hypotension/syncope: May cause orthostatic hypotension and syncope within a few hours after dosing, but may occur later; anticipate a similar effect if therapy is interrupted for a few days, if dosage is increased, or if another antihypertensive drug, PDE-5 inhibitor, or nitrates are introduced. Use with caution in patients with symptomatic orthostatic hypotension.

• Priapism: Priapism has been associated with use (rarely); seek immediate medical assistance for erections lasting longer than 4 hours.

Disease-related concerns:

• Cardiovascular disease: Use with caution in patients with heart failure, angina pectoris, or recent acute myocardial infarction (within the last 6 months). If symptoms of angina pectoris appear or worsen, discontinue use.

• Hepatic impairment: Use with caution in patients with mild-to-moderate impairment; not recommended in severe impairment (extensively metabolized); monitor blood pressure and for symptoms of hypotension in patients with mild-to-moderate impairment.

• Prostate cancer: Rule out prostatic carcinoma before beginning therapy (many symptoms of BPH and prostate cancer are similar).

Concurrent drug therapy issues:

• Drug-drug interactions: Potentially significant interactions may exist, requiring dose or frequency adjustment, additional monitoring, and/or selection of alternative therapy. Consult drug interactions database for more detailed information.

Dosage form specific issues:

• Extended release: Consists of drug within a nondeformable matrix; following drug release/absorption, the matrix/shell is expelled in the stool. The use of nondeformable products in patients with known stricture/narrowing of the GI tract has been associated with symptoms of obstruction. Use caution in patients with increased GI retention (eg, chronic constipation) as doxazosin exposure may be increased.

Other warning/precautions:

• Appropriate use: Extended release: Not indicated for use in women or for the treatment of hypertension.

Monitoring Parameters

Blood pressure routinely and for at least 6 hours after initial dose and with each dose increase (standing and sitting/supine); monitor patients with mild-to-moderate impairment for symptoms of hypotension.

Pregnancy Risk Factor

C

Pregnancy Considerations

Adverse events were observed in some animal reproduction studies. Doxazosin crosses the placenta (Versmissen 2016). Untreated chronic maternal hypertension is associated with adverse events in the fetus, infant, and mother. If treatment for hypertension during pregnancy is needed, other agents are generally preferred (ACOG, 2013).

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience fatigue, loss of strength and energy, or headache. Have patient report immediately to prescriber severe dizziness, passing out, angina, shortness of breath, swelling of arms or legs, or priapism (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience and judgment in diagnosing, treating, and advising patients.

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