terazosin hydrochloride

terazosin hydrochloride

(ter ay' zoe sin)

Hytrin

Pregnancy Category C

Drug classes

Antihypertensive

Alpha₁-adrenergic blocker

Therapeutic actions

Selectively blocks postsynaptic alpha₁-adrenergic receptors, decreasing sympathetic tone on the vasculature, dilating arterioles and veins, and lowering supine and standing BP; unlike conventional alpha-adrenergic blocking agents (eg, phentolamine), it does not also block alpha₂ presynaptic receptors, does not cause reflex tachycardia. Relaxes the smooth muscle by blocking alpha₁-adrenergic receptors in the bladder neck and prostate thereby improving the symptoms of BPH.

Indications

·        Treatment of symptomatic BPH

·        Treatment of hypertension alone or in combination with other drugs

·        Unlabeled use: Symptomatic treatment of chronic abacterial prostatitis

Contraindications and cautions

·        Contraindicated with hypersensitivity to terazosin, and during lactation.

·        Use cautiously in patients taking other antihypertensives, CHF, renal failure, pregnancy.

Available forms

Capsules—1, 2, 5, 10 mg

Dosages

ADULTS

Adjust dose and dosing interval (12 or 24 hr) individually.

·        Hypertension: Initial dose, 1 mg PO hs. Do not exceed 1 mg; strictly adhere to this regimen to avoid severe hypotensive reactions. Slowly increase dose to achieve desired BP response. Usual range, 1–5 mg PO daily. Up to 20 mg/day has been beneficial. Monitor BP 2–3 hr after dosing to determine maximum effect. If response is diminished after 24 hr, consider increasing dosage or use a twice daily regimen. If drug is not taken for several days, restart with initial 1-mg dose.

·        BPH: Initial dose, 1 mg PO hs. Increase to 2, 5, or 10 mg PO daily. 10 mg/day for 4–6 wk may be required to assess benefit. If drug is not taken for several days, restart with the initial dose.

PEDIATRIC PATIENTS

Safety and efficacy not established.

Pharmacokinetics

Route	Onset	Peak
Oral	Varies	1 hr

Metabolism: Unknown; T_1/2: 12 hr

Distribution: Crosses placenta; may enter breast milk

Excretion: Feces and urine

Adverse effects

·        CNS: Dizziness, headache, drowsiness, lack of energy, weakness, somnolence, nervousness, vertigo, depression, paresthesia

·        CV: Palpitations, sodium and water retention, increased plasma volume, edema, syncope, tachycardia, orthostatic hypotension, angina

·        Dermatologic: Rash, pruritus, alopecia

·        EENT: Blurred vision, reddened sclera, epistaxis, tinnitus, dry mouth, nasal congestion

·        GI: Nausea, vomiting, diarrhea, constipation, abdominal discomfort or pain

·        GU: Urinary frequency, incontinence, impotence, priapism

·        Respiratory: Dyspnea, nasal congestion, sinusitis

·        Other: Diaphoresis

Nursing considerations

Assessment

·        History: Hypersensitivity to terazosin; CHF; renal failure; pregnancy, lactation

·        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, urinary output; renal function tests, urinalysis

Interventions

·        WARNING: Administer or have patient take first dose just before bedtime to lessen likelihood of first dose effect, syncope, believed due to excessive orthostatic hypotension.

·        WARNING: Have patient lie down, and treat supportively if syncope occurs; condition is self-limiting.

·        Monitor patient for orthostatic hypotension, which is most marked in the morning, and is accentuated by hot weather, alcohol, exercise.

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

Teaching points

·        Take this drug exactly as prescribed. Take the first dose just before bedtime. Do not drive or operate machinery for 4 hours after the first dose.

·        You may experience these side effects: Dizziness, weakness (more likely to occur when you change position, in the early morning, after exercise, in hot weather, and with alcohol use; some tolerance may occur after taking the drug for a while, but avoid driving or engaging in tasks that require alertness; change position slowly; use caution when climbing stairs; lie down for a while if dizziness persists); GI upset (eat frequent small meals); impotence; dry mouth (suck on sugarless lozenges or ice chips); stuffy nose. Most effects will gradually disappear.

·        Report frequent dizziness or faintness.

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