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Prazosin information from DrugsUpdate  

See Available Brands of Prazosin in India

P - Contraindicated in pregnancy
L - Caution when used during lactation
LI - Lab *

Prazosin, trade names Minipress,Vasoflex and Hypovase, is a sympatholytic drug used to treat high blood pressure (hypertension). It belongs to the class of alpha-adrenergic blockers, which lower blood pressure by relaxing blood vessels. Specifically, prazosin is selective for the alpha-1 receptors on vascular smooth muscle. These receptors are responsible for the vasoconstrictive action of norepinephrine, which would normally raise blood pressure. By blocking these receptors, prazosin reduces blood pressure.

Pharmacodynamics

Pharmacokinetics

Prazosin competitively blocks postsynaptic α1-adrenoceptors of veins and arterioles causing vasodilation and reduction in blood pressure. The effect is seen in resistant vessels. There is no reflex tachycardia. Diastolic pressure reduced to a greater extent.

Absorption
Readily absorbed from the GIT; peak plasma concentrations after 1-3 hours (oral).

Distribution
Small amounts enter the breast milk. Protein-binding: High.

Metabolism
Extensively hepatic.

Excretion
Faeces (5-11% as unchanged drug; metabolites); urine (<10%); 2-4 hours (elimination half-life).

Prazosin Indications / Prazosin Uses

Information Not Available

Prazosin Adverse Reactions / Prazosin Side Effects

Postural hypotension, syncope, palpitations, lack of energy, nausea, oedema, chest pain, dyspnoea, constipation, diarrhoea, vomiting, depression, nervousness, sleep disturbances, headache, lassitude, drowsiness, loss of consciousness, dizziness, vertigo, hallucinations, paraesthesia, nasal congestion, epistaxis, dry mouth, urinary frequency and incontinence, pruritus, rash.

Potentially Fatal: Rarely, hypotension may be life-threatening.

Precautions

Overdosage
Severe hypotension may occur. May be treated with activated charcoal if patient presents within 1 hour of ingestion.

Special Precautions

Angina pectoris. Ability to drive or operate machinery may be impaired. Phaeochromocytoma, abrupt withdrawal, impaired renal and liver function. child <12 years. Lactation. May develop tolerance in prolonged treatment. Intiate treatment with low doses.

Other Drug Interactions

May increase plasma concentrations of digoxin. Antihypertensive effect enhanced by other antihypertensive drugs. Diuretics and alcohol. Risk of 1st dose hypotension is increased in patients receiving β-blockers or calcium-channel blockers.

Other Interactions

Information Not Available

Dosage

Oral
Hypertension
Adult: As hydrochloride: Initially, 500 mcg bid-tid for 3-7 days, increased to 1 mg bid-tid for the next 3-7 days if tolerated, and gradually increased thereafter according to patient's response. Max dose: 20 mg daily.

Oral
Heart failure
Adult: As hydrochloride: Initially, 500 mcg bid-qid, gradually increased according to response. Maintenance: 4-20 mg daily.

Oral
Raynaud's syndrome
Adult: Initially, 500 mcg bid, increased to a maintenance dose of ≤2 mg bid.

Oral
Benign prostatic hyperplasia
Adult: Initially, 500 mcg bid, increased to a maintenance dose of ≤2 mg bid.

Food(before/after)

May be taken with or without food. (Starting dose is best taken w/ dinner, at least 2-3 hours before retiring. Maintenance doses may be taken w/ or without meals.)

List of Contraindications

Prazosin and Pregnancy

Contraindicated in pregnancy

Category C: Either studies in animals have revealed adverse effects on the foetus (teratogenic or embryocidal or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the foetus.

Prazosin and Lactation

Caution when used during lactation

Prazosin and Children

Safety and efficacy not established.

Prazosin and Geriatic

Information Not Available

Prazosin and Other Contraindications

Overdosage
Severe hypotension may occur. May be treated with activated charcoal if patient presents within 1 hour of ingestion.

Storage

Information Not Available

Lab interference

Information Not Available

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