prazosin hydrochloride (redirected from Hypovase)

prazosin hydrochloride

[prä′zəsin]

an antihypertensive, peripherally acting alpha₁-adrenergic blocker.

indications It is prescribed to treat hypertension and to decrease afterload in congestive heart disease. Unlabeled uses include treatment of benign prostatic hyperplasia and Raynaud's phenomenon.

contraindications Known hypersensitivity to this or similar drugs (e.g., terazosin, doxazosin) prohibits its use.

adverse effects The initial dose of the medication can cause a large drop in blood pressure and syncope, especially in patients who are volume depleted or are concurrently using beta blockers. Common ongoing adverse effects include tachycardia, palpations, orthostatic hypotension, fainting, dizziness, headache, drowsiness, urinary urgency, weakness, and nausea. Rarely cataracts have appeared or worsened with the use of prazosin.

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prazosin hydrochloride

Hypovase (UK), Minipress

Pharmacologic class: Alpha₁-adrenergic blocker (peripherally acting)

Therapeutic class: Antihypertensive

Pregnancy risk category C

Action

Induces peripheral vasodilation by blocking postsynaptic alpha₁-adrenergic receptors, thereby lowering blood pressure. Decreases smooth muscle contractions of prostatic capsule and relaxes smooth muscles in bladder neck and prostate.

Availability

Capsules: 1 mg, 2 mg, 5 mg

⊘Indications and dosages

➣ Hypertension

Adults: Initially, 1 mg P.O. two or three times daily for 3 days, with first dose at bedtime; increase gradually to a maintenance dosage of 6 to 15 mg/day given in two or three divided doses.

Off-label uses

• Benign prostatic hypertrophy

Contraindications

• Hypersensitivity to drug or other quinazoline alpha₁-adrenergic blockers

Precautions

Use cautiously in:
• renal insufficiency, angina pectoris, hepatic impairment
• patients receiving diuretics concurrently
• pregnant or breastfeeding patients
• children (safety not established).

Administration

• Give test dose of 1 mg at bedtime to prevent first-dose syncope.
• Don't stop therapy suddenly. Dosage must be tapered.

Adverse reactions

CNS: dizziness, headache, asthenia, drowsiness, depression, syncope

CV: first-dose orthostatic hypotension, palpitations, angina

EENT: blurred vision, nasal congestion, epistaxis

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

GU: erectile dysfunction, priapism

Musculoskeletal: joint and bone pain, myalgia

Other: edema

Interactions

Drug-drug. Antihypertensives, nitrates: additive hypotension

Nonsteroidal anti-inflammatory drugs: decreased antihypertensive effect

Drug-diagnostic tests. Pheochromocytoma screening test: false-positive result

Sodium, urinary vanillylmandelic acid: increased levels

Drug-herbs. Ephedra (ma huang): acute hypertension

Patient monitoring

• After first dose, observe closely for hypotension and syncope.
• Monitor blood pressure and pulse. Watch for orthostatic hypotension.

Patient teaching

• Caution patient not to stop therapy suddenly. Dosage must be tapered.
• Tell patient drug may cause headache, muscle aches, or bone pain. Encourage him to discuss activity recommendations and pain management with prescriber.
• Inform patient that drug may cause sexual dysfunction. Advise him to discuss this issue with prescriber.
• Instruct patient to move slowly when sitting up or standing, to avoid dizziness from sudden blood pressure decrease.
• As appropriate, review all other significant adverse reactions and interactions, especially those related to the drugs, tests, and herbs mentioned above.