MINIPRESS

What it is

MINIPRESS is prazosin hydrochloride, available in tablet strengths of 1 mg, 2 mg and 5 mg prazosin base. The 1 mg tablet is orange and capsule-shaped; the 2 mg tablet is white and round; and the 5 mg tablet is white and diamond-shaped. Prazosin causes a decrease in total peripheral resistance through blockade of post-synaptic alpha-adrenoceptors.

Approved indications

— Hypertension of varied aetiology and all grades of severity. — Severe refractory congestive heart failure. — Raynaud's phenomenon and Raynaud's disease. — Symptomatic treatment of urinary obstruction caused by benign prostatic hyperplasia in patients awaiting prostatic surgery.

Dosing overview

Patient toleration is best when therapy is initiated with a low starting dose, adjusted on the basis of the patient's individual blood pressure response. For patients with moderate to severe renal impairment, therapy should be initiated at 0.5 mg daily with dose increases instituted with caution.

Key safety warnings

MINIPRESS may cause syncope with sudden loss of consciousness, usually believed to be due to an excessive postural hypotensive effect, although occasionally preceded by severe tachycardia with heart rates of 120–160 beats per minute. Syncopal episodes have usually occurred within 30 to 90 minutes of the initial dose or in association with rapid dosage increases or introduction of another antihypertensive drug. The incidence of syncope is approximately 1% in patients given an initial dose of 2 mg or greater; syncopal episodes can be minimised by limiting the initial dose to 0.5 mg, increasing dosage slowly and introducing additional antihypertensive drugs cautiously. Prolonged erections and priapism have been reported with alpha-1 blockers including prazosin; if an erection persists longer than 4 hours, the patient should seek immediate medical assistance, as untreated priapism could result in penile tissue damage and permanent loss of potency. In patients with acute or chronic left ventricular failure who have undergone vigorous diuretic and vasodilator treatment, a low initial dose of MINIPRESS and gradual titration with close observation is recommended. In occasional patients, clinical efficacy has diminished due to tolerance to prazosin's haemodynamic effects, with evidence of efficacy for periods exceeding 6 months lacking.

Contraindications

MINIPRESS is contraindicated in patients with a known sensitivity to quinazolines, prazosin or any other component of the tablets.

PBS listing

No source document contains information about PBS listing for MINIPRESS.

Regulatory history

MINIPRESS was first approved on 19 July 1991. ARTG registration records show three strengths: 1 mg, 2 mg and 5 mg prazosin hydrochloride tablets, all first listed on 1991-07-19 under licence category RE (Registered Establishment).