prazosin hydrochloride: clinical use

Prescribing considerations

• Postural hypotension and syncope can occur, particularly during initiation or treatment adjustment; older people may be more susceptible.
• Use cautiously with hepatic or moderate-to-severe renal impairment because response may be increased or evidence is limited.
• For benign prostatic hyperplasia in a patient also receiving antihypertensive therapy, coordinate management with the clinician responsible for hypertension.
• Record current or previous alpha-1 blocker exposure before cataract surgery because of possible intraoperative floppy iris syndrome.
• In heart failure, reassess weight gain, peripheral oedema or declining benefit because fluid retention may accompany reduced clinical response.

Contraindications and cautions

• Hypersensitivity to prazosin, another quinazoline or any product excipient
• Avoid for benign prostatic hyperplasia in patients with a history of micturition syncope
• Not recommended for heart failure caused by mechanical obstruction, including significant valve stenosis, pulmonary embolism or restrictive pericardial disease

Monitoring

• Supine and standing blood pressure, especially when treatment begins or changes
• Dizziness, syncope and falls risk
• Cardiopulmonary status, weight and peripheral oedema in heart failure
• Symptom response in Raynaud’s phenomenon or benign prostatic hyperplasia
• Adverse effects when combined with other blood-pressure-lowering medicines

Clinical pharmacology

Prazosin selectively antagonises postsynaptic alpha-1 adrenoceptors, producing balanced arterial and venous vasodilation. It is highly protein-bound, undergoes extensive hepatic metabolism and is eliminated mainly through bile and faeces.

Formulation and product differences

• The selected product is a conventional oral tablet rather than a modified-release preparation.
• The selected tablet is described as essentially sodium-free.

Tablet

Route: Oral

Strengths: 0.5 mg