doxazosin (dox-ay-zoe-sin) Cardura, Cardura XL

 Indications

Hypertension (alone or with other agents) (immediaterelease

only). Symptomatic benign prostatic hyperplasia

(BPH).

Action

Dilates both arteries and veins by blocking postsynaptic

alpha1-adrenergic receptors. Therapeutic Effects:

Lowering of BP. Increased urine flow and decreased

symptoms of BPH.

Pharmacokinetics

Absorption: Well absorbed following oral administration.

Distribution: Probably enters breast milk; rest of

distribution unknown.

Protein Binding: 98–99%.

Metabolism and Excretion: Extensively metabolized

by the liver.

Half-life: 22 hr.

TIME/ACTION PROFILE

ROUTE ONSET PEAK DURATION

PO† 1–2 hr 2–6 hr 24 hr

PO-XL‡ 5 wk unknown unknown

† Antihypertensive effect.

‡ Improved urinary flow and BPH symptoms.

Contraindications/Precautions

Contraindicated in: Hypersensitivity.

Use Cautiously in: Hepatic dysfunction; Gastrointestinal

narrowing (XL only); Geri: Appears on Beers

list. Geriatric patients are atqrisk for hypotension; OB,

Lactation, Pedi: Safety not established; Patients undergoing

cataract surgery (qrisk of intraoperative floppy

iris syndrome).

Adverse Reactions/Side Effects

CNS: dizziness, headache, depression, drowsiness, fatigue,

nervousness, weakness . EENT: abnormal vision,

blurred vision, conjunctivitis, epistaxis, intraoperative floppy iris syndrome. Resp: dyspnea. CV:

first-dose orthostatic hypotension, arrhythmias, chest

pain, edema, palpitations. GI: abdominal discomfort,

constipation, diarrhea, dry mouth, flatulence, nausea,

vomiting. GU:plibido, priapism, sexual dysfunction.

Derm: flushing, rash, urticaria. MS: arthralgia, arthritis,

gout, myalgia.

Interactions

Drug-Drug:qrisk of hypotension with sildenafil,

tadalafil, vardenafil, other antihypertensives, nitrates,

or acute ingestion of alcohol. NSAIDs, sympathomimetics,

or estrogens maypeffects of antihypertensive

therapy.

Route/Dosage

Hypertension

PO (Adults): —1 mg once daily, may be graduallyq

at 2-wk intervals to 2–16 mg/day; incidence of postural

hypotension greatlyqat doses 4 mg/day. BPH—1 mg

once daily, may be gradually increased to 8 mg/day.

Benign Prostatic Hyperplasia

PO (Adults): Immediate release—1 mg once daily,

may beqevery 1–2 wk up to 8 mg/day; Extended release—

4 mg once daily (with breakfast), may beqin

3–4 wk to 8 mg/day.

Availability (generic available)

Tablets: 1 mg, 2 mg, 4 mg, 8 mg. Cost: Generic—1

mg $60.00/100, 2 mg $79.89/100, 4 mg $85.34/100, 8

mg $60.41/100. Extended-release tablets: 4 mg, 8

mg. Cost: 4 mg $84.62/30, 8 mg $88.90/30.