terazosin hydrochloride

Action

Blocks postsynaptic alpha₁-adrenergic receptors, causing vasodilation and decreasing smooth muscle contractions in bladder neck and prostate

Availability

Capsules: 1 mg, 2 mg, 5 mg, 10 mg

Indications and dosages

➣ Hypertension

Adults: Initially, 1 mg P.O., increased slowly as needed up to 5 mg/day. Usual range is 1 to 5 mg/day, not to exceed 20 mg/day.

➣ Benign prostatic hyperplasia

Adults: 1 mg P.O. at bedtime. To achieve desired response, may increase gradually to 2 mg/day, then to 5 mg/day, and then to a maximum of 10 mg/day.

Contraindications

• Hypersensitivity to drug or other quinazoline derivatives

Precautions

Use cautiously in:

• prostate cancer, hepatic disease, dehydration, volume or sodium depletion

• pregnant or breastfeeding patients

• children (safety not established).

Administration

Don't stop therapy suddenly. Dosage must be tapered.

• Know that drug may be given as a single dose at bedtime or in two divided doses.

Adverse reactions

CNS: dizziness, headache, weakness, drowsiness, nervousness, paresthesia, vertigo, fatigue, syncope

CV: orthostatic hypotension (with first dose), rebound hypertension, chest pain, palpitations, peripheral edema, tachycardia, arrhythmias

EENT: blurred vision, conjunctivitis, amblyopia, nasal congestion, sinusitis

GI: nausea, vomiting, diarrhea, abdominal pain, dry mouth

GU: urinary frequency or incontinence, erectile dysfunction, priapism

Musculoskeletal: joint, back, and extremity pain; arthritis

Respiratory: dyspnea

Skin: pruritus

Other: fever, weight gain, flulike symptoms

Interactions

Drug-drug. Estrogens, nonsteroidal anti-inflammatory drugs (NSAIDs), sympathomimetics: decreased antihypertensive effects

Midodrine: antagonism of terazosin's action

Nitrates, other antihypertensives: additive hypotension

Drug-herbs. Ephedra (ma huang): antagonism of terazosin's action

Drug-behaviors. Alcohol use: additive hypotension

Patient monitoring

• Monitor blood pressure. Stay alert for orthostatic hypotension (first-dose effect) when therapy begins.

• Assess cardiovascular status. Report chest pain, peripheral edema, palpitations, and other significant effects.

Patient teaching

• Instruct patient to take at same time every day, with or without food.

Caution patient not to stop therapy abruptly. Dosage must be tapered.

Advise patient to immediately report swelling, breathing difficulty, palpitations, chest pain, and other cardiovascular reactions.

• Tell patient drug may cause erectile dysfunction and other sexual problems.

• Caution patient not to use NSAIDs or drink alcohol.

• Instruct patient to move slowly when sitting up or standing, to avoid dizziness from sudden blood pressure decrease.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, herbs, and behaviors mentioned above.