Doxazosin


Concise Prescribing Info
Indications/Uses
Listed in Dosage.
Dosage/Direction for Use
Adult : PO HTN Initial: 1 mg at bedtime. Maintenance: Up to 4 mg once daily. Max: 16 mg/day. Extended-release: Initial: 4 mg once daily, may increase to max 8 mg once daily after 4 wk. Benign prostatic hyperplasia Initial: 1 mg at bedtime, may be doubled at 1-2 wk intervals. Maintenance: 2-4 mg/day. Max: 8 mg/day. Extended-release: Initial: 4 mg once daily, may increase to max 8 mg once daily after 4 wk.
Dosage Details
Oral
Hypertension
Adult: Initially, 1 mg at bedtime, may be doubled at 1-2 wk intervals according to response. Maintenance: Up to 4 mg once daily. Max: 16 mg/day. Extended-release: Initially, 4 mg once daily, may increase to max 8 mg once daily after 4 wk.

Oral
Benign prostatic hyperplasia
Adult: Initially, 1 mg at bedtime, may be doubled at 1-2 wk intervals according to response. Maintenance: 2-4 mg/day. Max: 8 mg/day. Extended-release: Initially, 4 mg once daily, may increase to max 8 mg once daily after 4 wk.
Administration
May be taken with or without food.
Contraindications
Patient w/ history of orthostatic hypotension; benign prostatic hyperplasia and concomitant congestion of the upper urinary tract, chronic urinary tract infection or bladder stones; monotherapy in patients w/ either overflow bladder or anuria w/ or w/o progressive renal insufficiency.
Special Precautions
Prostatic carcinoma should be ruled out before starting therapy. Hepatic impairment. Pregnancy and lactation.
Adverse Reactions
Orthostatic hypotension may occur at the initiation of therapy or during dose increase, Intraoperative Floppy Iris Syndrome (IFIS) during cataract surgery, hypotension, syncope, palpitations, chest pain, dizziness, headache, drowsiness, lethargy, fatigue, nausea, abdominal pain, diarrhoea, dry mouth, oedema, rhinitis, dyspnoea, arthralgia/arthritis, muscle weakness, myalgia, muscle cramps, pruritus, rash, facial oedema, polyuria, urinary incontinence, visual abnormalities, tinnitus; reduced leukocyte and neutrophil counts. Rarely, priapism can occur.
Patient Counseling Information
May impair ability to drive and operate machinery.
MonitoringParameters
Monitor BP and renal function.
Overdosage
Symptoms: Hypotension. Management: Place patient in supine, head down position. If necessary, a vasopressor may be used.
Drug Interactions
Concomitant admin w/ phosphodiesterase type 5 (PDE5) inhibitors (e.g. sildenafil) may lead to symptomatic hypotension. Potentiates the BP lowering activity of other α-blockers and other antihypertensives.
Action
Description: Doxazosin competitively blocks the α1-adrenoceptors on postsynaptic effector cells in arteriolar and venous vascular beds resulting in vasodilation of veins and arterioles and decrease in total peripheral resistance and BP.
Duration: >24 hr.
Pharmacokinetics:
Absorption: Well absorbed from the GI tract. Bioavailability: Approx 65%. Time to peak plasma concentration: 2-3 hr.
Distribution: Plasma protein binding: Approx 98%.
Metabolism: Extensively hepatic primarily via CYP3A4, secondary pathways via CYP2D6 and CYP2C19.
Excretion: Via faeces as metabolites and as unchanged drug (small amount). Terminal half-life: Approx 22 hr.
Storage
Store below 30°C.
References
Anon. Doxazosin. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com.

Buckingham R (ed). Doxazosin Mesilate. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com .

Cardura Tablets. U.S. FDA. https://www.fda.gov.

Doxazosin (Teva). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/.

McEvoy GK, Snow EK, Miller J et al (eds). Doxazosin Mesylate. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com.

Disclaimer: This information is independently developed by MIMS based on Doxazosin from various references and is provided for your reference only. Therapeutic uses, prescribing information and product availability may vary between countries. Please refer to MIMS Product Monographs for specific and locally approved prescribing information. Although great effort has been made to ensure content accuracy, MIMS shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2020 MIMS. All rights reserved. Powered by MIMS.com
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