Trade Names:Cardura- Tablets 1 mg- Tablets 2 mg- Tablets 4 mg- Tablets 8 mg
Trade Names:Cardura XL- Tablets, extended-release 4 mg- Tablets, extended-release 8 mgApo-Doxazosin (Canada)Cardura-1 (Canada)Cardura-2 (Canada)Cardura-4 (Canada)Gen-Doxazosin (Canada)
Selectively blocks postsynaptic alpha-1 adrenergic receptors, resulting in dilation of arterioles and veins.
Relative bioavailability of 4 and 8 mg dose is 54% and 59%, respectively, compared with immediate-release (IR) product. C max for 4 and 8 mg dose is 10.1 and 25.8 ng/mL, respectively. T max for 4 and 8 mg dose is 8 and 9 h, respectively. Food increases C max and AUC approximately 32% and 18%, respectively.IR tablets
T max is 2 to 3 h. Bioavailability is approximately 65%. Enterohepatic recycling. Food decreases C max 18% and AUC 12%.
Approximately 98% bound to plasma proteins (IR and ER).
First-pass metabolism; extensively metabolized by O-demethylation or hydroxylation to several active metabolites.
The t ½ is approximately 22 h.Feces
63% of dose; 4.8% as unchanged drug.Urine
9% of dose; trace amount as unchanged drug.
Elimination is biphasic.ER
Apparent elimination t ½ is 15 to 19 h.
40% increase in exposure.
Treatment of benign prostatic hyperplasia (BPH); treatment of hypertension, alone or in combination with other agents (IR only).
Hypersensitivity to doxazosin, prazosin, or terazosin.
4 mg once daily with breakfast. Dose may be increased to 8 mg after 3 to 4 wk (max, 8 mg once daily). If treatment is stopped for several days, restart therapy at 4 mg once daily.IR Initial dose
Increase to 2 mg, and thereafter to 4 and 8 mg every day, which is the max dose for BPH. Recommended titration interval is 1 to 2 wk.HypertensionAdults
1 mg every day.Maintenance
Based on standing BP response, may increase to 2 mg and thereafter to 4, 8, and 16 mg.
Store at 59° to 86°F.
10% increase in mean AUC of doxazosin.Tadalafil, vardenafil
BP-lowering effect of doxazosin may be increased. Alpha-1 adrenergic blockers (including doxazosin) are contraindicated in patients receiving tadalafil or vardenafil.
None well documented.
Hypotension, palpitation, postural hypotension (2%); arrhythmia (1%); palpitations, peripheral ischemia, syncope, tachycardia (less than 1%); bradycardia, cerebral vascular accidents, MI (postmarketing).
Dizziness (19%); headache (16%); fatigue/malaise (12%); asthenia (7%); somnolence (5%); vertigo (4%); nervousness (2%); anxiety, ataxia, depression, hypertonia, insomnia, kinetic disorder, paresthesia (1%); agitation, anorexia, hypesthesia (postmarketing).
Increased sweating, pruritus, rash (1%); alopecia, urticaria (postmarketing).
Rhinitis (3%); abnormal vision (2%); conjunctivitis/eye pain, epistaxis, tinnitus (1%); blurred vision, floppy iris syndrome (postmarketing).
Nausea (3%); abdominal pain, diarrhea, dry mouth, dyspepsia (2%); constipation, flatulence (1%); GI irritation and bleeding, vomiting (postmarketing).
Polyuria, sexual dysfunction (2%); impotence, urinary incontinence, UTI (1%); gynecomastia, hematuria, micturition disorder, micturition frequency, nocturia, priapism (postmarketing).
Leukopenia, purpura, thrombocytopenia (postmarketing).
Abnormal LFTs, cholestatic hepatitis, hepatitis, jaundice (postmarketing).
Back pain (3%); arthralgia/arthritis, muscle cramps, muscle weakness, myalgia (1%).
Respiratory tract infection (5%); dyspnea (3%); respiratory disorder (1%); aggravated bronchospasm (postmarketing).
Chest pain, pain (2%); face edema, flushing, influenza-like symptoms (1%); allergic reaction, hot flashes (postmarketing).
Monitor BP and pulse. Assess changes in urinary symptoms, such as dribbling, frequency, hesitancy, nocturia, volume, weak stream.
Category C .
Safety and efficacy not established.
Use of ER tablets in severe hepatic function impairment is not recommended.
Intraoperative floppy iris syndrome has occurred during cataract surgery in patients on or previously treated with alpha-1 blockers.
Marked hypotension (especially orthostatic) and syncope may occur 2 to 6 h after the first few doses, after reintroduction with rapid increase in dosing, or after addition of another antihypertensive.
Administer ER product with caution in patients with preexisting severe GI narrowing. Obstructive symptoms have occurred in patients with known strictures in association with ingestion of nondeformable ER formulations.
Mean WBC and neutrophil counts decreased 2.4% and 1%, respectively. No patients became symptomatic as a result of the low WBC or neutrophil count.
Slight decrease in total serum cholesterol and LDL may occur as well as increase in HDL.
Occurs rarely; may lead to permanent impotence if not promptly treated.
Rule out before starting therapy.
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