Adult: Initially, 0.5 mg bid for 3-7 days; adjust gradually according to patient’s response. Usual maintenance dose: 1-2 mg bid. Elderly: Initiate at the lower end of the dosing range.
Oral Congestive heart failure
Adult: Initially, 0.5 mg 2-4 times daily; increase gradually to 4 mg, according to response. Usual maintenance dose: 4-20 mg daily in divided doses. Elderly: Initiate at the lower end of the dosing range.
Adult: Initially, 0.5 mg bid or tid for 3-7 days to be taken in the evening, then increase to 1 mg bid or tid for the next 3-7 days, if tolerated. Then gradually increase up to Max 20 mg daily in divided doses according to response. Alternatively, initial dose of 1 mg bid or tid, then titrate dose up to 20 mg daily in 2-3 divided doses according to response. Elderly: Initiate at the lower end of the dosing range.
Oral Benign prostatic hyperplasia
Adult: As an adjunct: Initially, 0.5 mg bid for 3-7 days; adjust according to patient’s response. Usual maintenance dose: 2 mg bid. Elderly: Initiate at the lower end of the dosing range.
Special Patient Group
Patients taking other antihypertensives but with inadequate control: Initially, 0.5 mg in the evening, then continue with 0.5 mg bid or tid; increase gradually thereafter according to patient’s response.
Moderate to severe: Initially, 0.5 mg daily, increase cautiously.
Initially, 0.5 mg daily, increase cautiously.
May be taken with or without food. Starting dose is best taken w/ dinner, at least 2-3 hr before retiring. Maintenance doses may be taken w/ or w/o meals.
Patient with history of micturition syncope in the treatment of benign prostatic hyperplasia (BPH); CHF due to mechanical obstruction (e.g. aortic valve stenosis, mitral valve stenosis, pulmonary embolism, restrictive pericardial disease); ischaemic heart disease. Cataract surgery patient. Hepatic and moderate to severe renal impairment. Elderly. Pregnancy and lactation.
Significant: Syncope (with sudden loss of consciousness), orthostatic hypotension, priapism, prolonged erections, angina, CNS depression, intraoperative floppy iris syndrome. Cardiac disorders: Palpitations. Ear and labyrinth disorders: Vertigo. Eye disorders: Blurred vision. Gastrointestinal disorders: Diarrhoea, nausea, vomiting, dry mouth, constipation. General disorders and administration site conditions: Oedema, lack of energy, weakness. Nervous system disorders: Headache, dizziness, drowsiness, faintness. Psychiatric disorders: Depression, nervousness. Respiratory, thoracic and mediastinal disorders: Dyspnoea, nasal congestion. Skin and subcutaneous tissue disorders: Rash.
This drug may cause dizziness or weakness, if affected, do not drive or operate machinery.
Rule out prostate cancer before initiation of therapy. Monitor blood pressure and cardiac status.
Symptom: Hypotension. Management: Supportive treatment. Keep the patient in a supine position to restore blood pressure and normalise the heart rate. If inadequate, treat shock with volume expanders; vasopressors (including angiotensin) should be given if needed. Monitor renal function.
May cause symptomatic hypotension with phosphodiesterase type-5 (PDE-5) inhibitors (e.g. sildenafil, tadalafil, vardenafil). Additive hypotensive effect with diuretics or other antihypertensive agents.
May give false-positive results in screening tests for phaeochromocytoma urinary vanillylmandelic acid (VMA) and methoxyhydroxyphenyl glycol (MHPG) metabolites of norepinephrine.
Description: Mechanism of Action: Prazosin is an α-blocker that competitively inhibits postsynaptic α1-adrenoreceptors, resulting in peripheral dilatation of arteries and veins, and decrease in total peripheral resistance and blood pressure. Onset: Within 2 hours (antihypertensive). Duration: 10-24 hours. Pharmacokinetics: Absorption: Readily absorbed from the gastrointestinal tract. Bioavailability: 43-82%. Time to peak plasma concentration: 1-3 hours. Distribution: Crosses the placenta, enters breast milk. Volume of distribution: 0.5 L/kg. Plasma protein binding: 97%. Metabolism: Extensively metabolised in the liver via demethylation and conjugation. Excretion: Mainly via faeces (5-11% as unchanged drug); urine (<10%). Elimination half-life: 2-3 hours.
Store below 30°C. Protect from light and moisture.