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Doxazosin information from DrugsUpdate  

See Available Brands of Doxazosin in India

P - Caution when used during pregnancy
L - Caution when used during lactation

Doxazosin mesylate, a quinazoline compound sold by Pfizer under the brand names Cardura and Carduran, is an alpha blocker used to treat high blood pressure and benign prostatic hyperplasia.
It is an alpha-1 adrenergic receptor blocker that inhibits the binding of norepinephrine to alpha receptors in the autonomic nervous system. The primary effect of this blockage is relaxed vascular smooth muscle tone (vasodilation), which decreases peripheral vascular resistance, leading to decreased blood pressure.

Pharmacodynamics

Pharmacokinetics

Doxazosin competitively blocks the α1-adrenoceptors on postsynaptic effector cells in arteriolar and venous vascular beds resulting in vasodilation of veins and decrease in total peripheral resistance and BP.
Onset: 2-6 hr (oral).
Duration: 24 hr.
Absorption: Well absorbed from the GI tract; peak plasma concentrations after 2 hr (oral).
Distribution: Protein-binding: Extensive.
Metabolism: Extensively hepatic.
Excretion: Faeces (small amounts as unchanged drug and as metabolites); 22 hr (elimination half-life); not removed by dialysis.

Doxazosin Indications / Doxazosin Uses

Information Not Available

Doxazosin Adverse Reactions / Doxazosin Side Effects

Chest pain, fatigue, headache, influenza-like symptoms, pain, hypotension, palpitation, abdominal pain, diarrhoea, nausea, oedema, dizziness, dry mouth, somnolence, dyspnoea, respiratory disorders, vision abnormalities, impotence, urinary tract infection, increased sweating, anxiety, insomnia. Vertigo, orthostatic hypotension, arrhythmia, hypotension, arthralgia/arthritis, muscle weakness, myalgia, kinetic disorders, ataxia, hypertonia, muscle cramps, flushing, tinnitus, sexual dysfunction, rhinitis, epistaxis, polyuria, urinary incontinence, fatigue/malaise, face oedema.

Precautions

General
Prostate Cancer
Carcinoma of the prostate causes many of the symptoms associated with BPH and the two disorders frequently co-exist. Carcinoma of the prostate should therefore be ruled out prior to commencing therapy with Doxazosin mesylate.
Cataract Surgery
Intraoperative Floppy Iris Syndrome (IFIS) has been observed during cataract surgery in some patients on or previously treated with other alpha1 blockers.This variant of small pupil syndrome is characterized by the combination of a flaccid iris that billows in response to intraoperative irrigation currents, progressive intraoperative miosis despite preoperative dilation with standard mydriatic drugs, and potential prolapse of the iris toward the phacoemulsification incisions. The patient’s surgeon should be prepared for possible modifications to their surgical technique, such as the utilization of iris hooks, iris dilator rings, or viscoelastic substances. There does not appear to be a benefit of stopping alpha1 blocker therapy prior to cataract surgery.
Orthostatic Hypotension
While syncope is the most severe orthostatic effect of Doxazosin mesylate, other symptoms of lowered blood pressure, such as dizziness, lightheadedness, or vertigo can occur, especially at initiation of therapy or at the time of dose increases.
a) Hypertension
These symptoms were common in clinical trials in hypertension, occurring in up to 23% of all patients treated and causing discontinuation of therapy in about 2%.
In placebo-controlled titration trials in hypertension, orthostatic effects were minimized by beginning therapy at 1 mg per day and titrating every two weeks to 2, 4, or 8 mg per day. There was an increased frequency of orthostatic effects in patients given 8 mg or more, 10%, compared to 5% at 1-4 mg and 3% in the placebo group.
b) Benign Prostatic Hyperplasia
In placebo-controlled trials in BPH, the incidence of orthostatic hypotension with Doxazosin was 0.3% and did not increase with increasing dosage (to 8 mg/day). The incidence of discontinuations due to hypotensive or orthostatic symptoms was 3.3% with Doxazosin and 1% with placebo. The titration interval in these studies was one to two weeks.
Patients in occupations in which orthostatic hypotension could be dangerous should be treated with particular caution. As alpha1 antagonists can cause orthostatic effects, it is important to evaluate standing blood pressure two minutes after standing and patients should be advised to exercise care when arising from a supine or sitting position.
If hypotension occurs, the patient should be placed in the supine position and, if this measure is inadequate, volume expansion with intravenous fluids or vasopressor therapy may be used. A transient hypotensive response is not a contraindication to further doses of Doxazosin mesylate.

Special Precautions

Renal or hepatic impairment. Prostatic carcinoma should be ruled out before starting therapy. Orthostatic hypotension may occur at the initiation of therapy or when there is dose increase. Avoid driving or performing hazardous tasks for 24 hr after starting therapy or dose changes. Pregnancy and lactation.

Other Drug Interactions

Decreased hypotensive effect with NSAIDs. Increased hypotensive effect with β-blockers, diuretics, ACE inhibitors, calcium-channel blockers.

Other Interactions

Information Not Available

Dosage

Oral
Hypertension
Adult: As mesilate: Initially, 1 mg at bedtime increased after 1-2 wk according to response. Maintenance: 4 mg once daily. Max: 16 mg daily.
Oral
Benign prostatic hyperplasia
Adult: As mesilate: Initially, 1 mg once daily at bedtime increased after 1-2 wk; monitor BP after 2-6 hr. Maintenance: 2-4 mg daily. Max: 8 mg daily.


 

Food(before/after)

May be taken with or without food

List of Contraindications

Doxazosin and Pregnancy

Caution when used during pregnancy

Doxazosin and Lactation

Caution when used during lactation

Doxazosin and Children

The safety and effectiveness of Doxazosin mesylate as an antihypertensive agent have not been established in children.

Doxazosin and Geriatic

The safety and effectiveness profile of Doxazosin mesylate in BPH was similar in the elderly (age > 65 years) and younger (age < 65 years) patients.
For hypertension:
Clinical studies of Doxazosin Mesylate Tablets did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautions, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

Doxazosin and Other Contraindications

Known hypersensitivity to quinazolines

Storage

Information Not Available

Lab interference

Information Not Available

Doxazosin brands in India:

Alfazosin Doxacard Doxapress Duracard Duraten

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