Dosing and uses of Cardura, Cardura XL (doxazosin)
Adult dosage forms and strengths
tablet
- 1mg
- 2mg
- 4mg
- 8mg
tablet, extended release
- 4mg
- 8mg
Hypertension
Immediate release: 1-16 mg PO once daily in AM or Pm
Extended release: Not indicated for hypertension
Benign Prostatic Hyperplasia
Immediate release: 1-8 mg/day PO
Extended release: 4 mg/day PO initially at breakfast; may be increased to no more than 8 mg/day PO
Dosing Modifications
Hepatic impairment: Use with caution in mild-to-moderate hepatic dysfunction; do not use in severe impairment
Dosing Considerations
Give first dose and increase at bedtime to avoid syncope
Pediatric dosage forms and strengths
tablet
- 1mg
- 2mg
- 4mg
- 8mg
Hypertension (Off-label)
Immediate release: 1-4 mg PO once daily in AM or Pm
Geriatric dosage forms and strengths
Hypertension
Avoid use for hypertension; high risk of orthostatic hypotension (Beers criteria); if used, lower initial dosages and gradual adjustments are recommended
Immediate release: 0.5-16 mg PO once daily in AM or Pm
Extended release: Not indicated for hypertension
Benign Prostatic Hyperplasia
Immediate release: 1-8 mg/day PO
Extended release: 4 mg/day PO initially at breakfast; may be increased to no more than 8 mg/day PO
Cardura, Cardura XL (doxazosin) adverse (side) effects
>10%
Dizziness (5-19%)
Fatigue (8-12%)
Headache (6-10%)
1-10%
Vertigo (7%)
Upper respiratory tract infection (URTI) (5%)
Edema (3-4%)
Rhinitis (3%)
Dyspnea (1-3%)
Abdominal pain (2%)
Hypotension (1-2%)
Nausea (1-2%)
Orthostatic hypotension (dose related) (0.3-2%)
Anxiety (1%)
Palpitations (1%)
Postmarketing experience
Autonomic Nervous System: Priapism
Cardiovascular System: Cerebrovascular accidents, dizziness postural, myocardial infarction
Central and Peripheral Nervous System: Hypoesthesia, paresthesia
Endocrine System: Gynecomastia
Gastrointestinal System: Gastrointestinal obstruction, vomiting
General Body System: Fatigue, hot flushes, malaise
Heart Rate/Rhythm: Bradycardia, cardiac arrhythmias
Hematopoietic: Leukopenia, purpura, thrombocytopenia
Liver/Biliary System: Abnormal liver function tests, hepatitis, hepatitis cholestatic, jaundice
Musculoskeletal System: Muscle cramps, muscle weakness
Psychiatric: Agitation, anorexia, nervousness
Respiratory System: Bronchospasm aggravated
Skin Disorders: Alopecia, urticaria, skin rash, pruritus
Special Senses: Blurred vision, intraoperative Floppy Iris Syndrome
Urinary System: Hematuria, micturition disorder, micturition frequency, nocturia, polyuria
Warnings
Contraindications
Hypersensitivity to doxazosin or other quinazolines
Cautions
Use with caution in liver disease or recent cerebrovascular accident (CVA)
Rule out prostate cancer before initiating therapy
May cause first-dose syncope or sudden loss of consciousness
Risk of orthostatic hypotension (dose dependent)
Potential for hypotension, dry mouth, and urinary complications in elderly
Priapism (painful penile erection, sustained for hours and unrelieved by sexual intercourse or masturbation) rarely reported (probably less frequently than once in every several thousand patients), with alpha-1 antagonists, including doxazosin; because condition can lead to permanent impotence if not promptly treated, patients must be advised about seriousness of condition
Concomitant use of other antihypertensives (additive hypotensive effects)
Extended-release form not indicated for hypertension
Concomitant administration of immediate-release form with a phosphodiesterase-5 (PDE-5) inhibitor can result in additive blood pressure lowering effects and symptomatic hypotension
May increase the risk of heart failure by exacerbating underlying myocardial dysfunction by β1Receptor stimulation with increases in renin and aldosterone
Pregnancy and lactation
Pregnancy category: C
Lactation: Unknown whether drug is excreted in milk; use with caution
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Cardura, Cardura XL (doxazosin)
Mechanism of action
Hypertension: Blocks postsynaptic alpha1 receptors; alpha blockade causes arterial, arteriolar, and venous dilation; decreases total peripheral resistance and blood pressure
Benign prostatic hyperplasia (BPH): Blocks alpha1 receptors in prostatic stromal and bladder tissues; reduces sympathetic tone-induced urethral stricture responsible for BPH symptoms
Absorption
Bioavailability: Immediate release, 65%; extended release, 54-59%
Onset (antihypertensive response): Peak, 4-8 hr
Onset (BPH response): Initial, 2 wk; peak, 4-6 weeks
Duration: 24 hr
Peak plasma time: 2-3 hr
Distribution
Protein bound: 99%
Vd: 1-3.4 L/kg
Metabolism
Metabolized extensively in liver
Metabolites: 6- and 7-O-demethyl metabolites, 6'- and 7'-hydroxy metabolites, other minor metabolites (activity unknown)
Elimination
Half-life: Immediate release, 22 hr; extended release, 15-19 hr
Dialyzable: HD, no
Total body clearance: 83-140 mL/min
Excretion: Feces (65%), urine (0.6-9%)
