Doxazosin mesylate

doxazosin mesylate

(dox ay' zoe sin)

Cardura

Pregnancy Category C

Drug classes

Alpha-adrenergic blocker

Antihypertensive

Therapeutic actions

Reduces total peripheral resistance through alpha-blockade, causing an antihypertensive effect. The degree of smooth muscle tone in prostate/bladder neck is also mediated by alpha receptors. Its blockade reduces urethral resistance and removes obstructions.

Indications

·        Treatment of mild-to-moderate hypertension, alone or as part of combination therapy

·        BPH

Contraindications and cautions

·        Contraindicated with lactation.

·        Use cautiously with allergy to doxazosin, CHF, renal failure, pregnancy, hepatic impairment.

Available forms

Tablets—1, 2, 4, 8 mg

Dosages

ADULTS

·        Hypertension: Initially, 1 mg daily PO, given once daily. For maintenance, 2, 4, 8, or 16 mg daily PO, given once a day; dose may be increased q 2 wk.

·        BPH: Initially, 1 mg PO daily; for maintenance, may increase to 2 mg, 4 mg, and 8 mg daily, adjust at 1–2 wk intervals.

PEDIATRIC PATIENTS

Safety and efficacy not established.

Pharmacokinetics

Route	Onset	Peak
Oral	Varies	2–3 hr

Metabolism: Hepatic; T_1/2: 22 hr

Distribution: Crosses placenta; enters breast milk

Excretion: Bile, feces, urine

Adverse effects

·        CNS: Headache, fatigue, dizziness, postural dizziness, lethargy, vertigo, rhinitis, asthemia, anxiety, parasthesia, increased sweating, muscle cramps, insomnia, eye pain, conjunctivitis

·        CV: Tachycardia, palpitations, edema, orthostatic hypotension, chest pain

·        GI: Nausea, dyspepsia, diarrhea, abdominal pain, flatulence, constipation

·        GU: Sexual dysfunction, increased urinary frequency

·        Other: Dyspnea, increased sweating, rash

Interactions

Drug-drug

·        Increased hypotensive effects if taken with alcohol, nitrates, other antihypertensives

Nursing considerations

Assessment

·        History: Allergy to doxazosin, CHF, renal failure, hepatic impairment, lactation, pregnancy

·        Physical: Weight; skin color, lesions; orientation, affect, reflexes; ophthalmologic examination; P, BP, orthostatic BP, supine BP, perfusion, edema, auscultation; R, adventitious sounds, status of nasal mucous membranes; bowel sounds, normal output; voiding pattern, normal output; renal function tests, urinalysis

Interventions

·        Monitor edema, weight in patients with incipient cardiac decompensation, and arrange to add a thiazide diuretic to the drug regimen if sodium and fluid retention, signs of impending CHF occur.

·        WARNING: Monitor patient carefully with first dose; chance of orthostatic hypotension, dizziness and syncope are great with the first dose. Establish safety precautions.

·        Monitor signs and symptoms of BPH to adjust dosage.

Teaching points

·        Take this drug exactly as prescribed, once a day. Dizziness or syncope may occur at beginning of therapy. Change position slowly to avoid increased dizziness.

·        You may experience these side effects: Dizziness, weakness (when changing position, in the early morning, after exercise, in hot weather, and after consuming alcohol; some tolerance may occur after a while; avoid driving or engaging in tasks that require alertness; change position slowly, use caution in climbing stairs, lie down if dizziness persists); GI upset (eat frequent small meals); impotence; stuffy nose; most of these effects gradually disappear with continued therapy.

·        Report frequent dizziness or fainting.

Adverse effects in Italic are most common; those in Bold are life-threatening.