Schedule H

Oral

• Tablets (Immediate-release): 1 mg, 2 mg, 4 mg

• Tablets (Extended-release/GITS): 4 mg, 8 mg

INDICATIONS + DOSING — FOR CLINICIAN USE ONLY

Primary Indications (Approved / Standard in India)

1. Essential Hypertension

Parameter Recommendation

Starting dose: 1 mg once daily at bedtime

Titration: Increase to 2 mg after 1–2 weeks, then to 4 mg, then 8 mg at similar intervals based on BP response

Usual maintenance dose: 2–4 mg once daily

Maximum dose: 16 mg/day (rarely required; efficacy plateaus beyond 8 mg)

Clinical notes:

• Bedtime initiation reduces first-dose hypotension risk

• Not recommended as first-line monotherapy for hypertension (ALLHAT evidence: increased heart failure risk compared to diuretics)

• Useful as add-on therapy when CCBs, ACE inhibitors, or diuretics insufficient

• Particularly beneficial when hypertension co-exists with BPH in males

• Correct volume depletion before initiating therapy

1. Symptomatic Benign Prostatic Hyperplasia (BPH)

Parameter Recommendation

Starting dose: 1 mg once daily at bedtime

Titration: Increase to 2 mg after 1–2 weeks, then to 4 mg based on LUTS improvement and tolerability

Usual maintenance dose: 2–4 mg once daily

Maximum dose: 8 mg/day

Clinical notes:

• Provides symptomatic relief of dynamic urinary obstruction

• Relaxes smooth muscle of prostate and bladder neck

• Does not reduce prostate volume or alter disease progression

• Effect on LUTS typically seen within 1–2 weeks

• Long half-life permits once-daily dosing (advantage over prazosin)

Secondary Indications — Adults (Off-label)

Indication Dose Duration Notes

PTSD-associated nightmares (OFF-LABEL) Starting dose: 1 mg at bedtime; Titration: increase by 1 mg weekly; Usual dose: 2–6 mg at bedtime; Maximum: 8 mg/night Continue if benefit seen; reassess every 4–8 weeks Specialist only (Psychiatry). Evidence: RCTs demonstrating efficacy; used in Indian psychiatric specialist practice

Chronic prostatitis/pelvic pain syndrome (OFF-LABEL) Starting dose: 1 mg once daily; Titration: up to 4 mg once daily 6–12 weeks trial Specialist only (Urology). Evidence: Limited RCT data; used in Indian urology practice

PAEDIATRIC DOSING (Specialist Only)

Primary Indications (Approved / Standard in India)

Not approved for routine paediatric use in India.

Secondary Indications — Paediatrics (Off-label)

Indication Age Dose Notes

Refractory Hypertension (OFF-LABEL) >2 years Starting dose: 0.02–0.05 mg/kg once daily; Titration: every 1–2 weeks based on BP; Maximum: 0.4 mg/kg/day or 4 mg/day (whichever lower) Specialist only (Paediatric Nephrology/Cardiology). Evidence: Limited; based on extrapolation and specialist practice

Safety monitoring:

• Blood pressure (supine and standing) before each dose escalation

• Monitor for dizziness, syncope, orthostatic symptoms

• First-dose effect precaution: administer at bedtime

Minimum age statement: Not recommended below 2 years of age. Use only in children ≥2 years under paediatric nephrology or cardiology supervision in tertiary care settings.

• Hypersensitivity to doxazosin or other quinazoline derivatives (e.g., prazosin, terazosin)

• Severe hepatic impairment

• Monotherapy in patients with overflow incontinence or anuria (urological contraindication)

• Concurrent use with other alpha-1 blockers

• First-dose hypotension — initiate at bedtime; advise patient to lie down if symptomatic

• History of orthostatic hypotension or syncope

• Volume depletion or concurrent diuretic therapy

• Elderly patients — increased fall risk

• Heart failure — not recommended as first-line; may worsen outcomes (ALLHAT data)

• Planned cataract surgery — risk of intraoperative floppy iris syndrome (IFIS); inform ophthalmologist

• Recent myocardial infarction — initiate only after haemodynamic stabilisation

• Concurrent PDE-5 inhibitor therapy — stagger dosing

• Avoid abrupt withdrawal after prolonged therapy

Parameter Information

Overall safety: Limited human data; no clear teratogenicity in animal studies

Risk category: Not formally classified in India; avoid unless clearly necessary

Preferred alternatives: Labetalol, methyldopa, nifedipine (for pregnancy-induced hypertension)

When may be used: Only when standard agents contraindicated and potential benefit justifies risk; specialist supervision mandatory

What to monitor: Maternal BP (supine and standing), fetal growth, uteroplacental perfusion

Parameter Information

Compatible with breastfeeding: Caution advised; likely excreted in milk

Drug levels in milk: Not well quantified; expected to be low based on drug properties

Preferred alternatives: Amlodipine, methyldopa, labetalol (better studied during lactation)

What to monitor in infant: Feeding adequacy, excessive sedation, lethargy, poor weight gain

Parameter Recommendation

Starting dose: 1 mg once daily at bedtime (lowest available tablet strength)

Titration: Very slow — increase at intervals of 2 weeks or longer

Extra risks: Postural hypotension, syncope, falls with fractures, dizziness, confusion, urinary retention (paradoxical in some cases)

Special considerations: Review concurrent medications (diuretics, other antihypertensives, psychotropics); ensure adequate hydration; counsel on slow positional changes

Interacting Drug Effect Recommendation

PDE-5 inhibitors (sildenafil, tadalafil, vardenafil) Severe additive hypotension Ensure doxazosin dosing is stable before initiating PDE-5 inhibitor; use lowest PDE-5 inhibitor dose; stagger administration by ≥4 hours

Other alpha-1 blockers (prazosin, tamsulosin, alfuzosin) Excessive alpha-blockade; profound hypotension Avoid combination

Strong CYP3A4 inhibitors (ketoconazole, itraconazole, ritonavir, clarithromycin) Increased doxazosin plasma levels Avoid combination or use with extreme caution; consider dose reduction

Potent vasodilators (nitrates, hydralazine) Marked additive hypotension Avoid concurrent initiation; careful dose adjustment if combined

Interacting Drug Effect Recommendation

Beta-blockers Additive hypotension; potential for first-dose effect enhancement Can be used together; monitor BP carefully during initiation

Diuretics Synergistic BP lowering; increased orthostatic hypotension risk May need to reduce or temporarily hold diuretic during doxazosin initiation

Calcium channel blockers Additive vasodilation and hypotension Monitor BP; dose adjustment may be needed

NSAIDs May blunt antihypertensive effect Monitor BP; consider paracetamol as alternative analgesic

Tricyclic antidepressants Additive hypotension Monitor closely; counsel patient

Alcohol Enhanced hypotensive effect Counsel to limit alcohol, especially during initiation

Rifampicin May reduce doxazosin levels (CYP3A4 induction) Monitor BP; may require higher doxazosin dose

Warfarin No major pharmacokinetic interaction Monitor INR with any significant BP or volume changes

• Dizziness (most frequent)

• Headache

• Fatigue and somnolence

• Postural hypotension

• Peripheral oedema

• Palpitations

• Nasal congestion/rhinitis

• Asthenia

• Nausea

Adverse Effect Clinical Action

First-dose syncope Have patient lie down; assess volume status; restart at lower dose with bedtime administration once stable

Severe hypotension IV fluids; rarely vasopressors; hospitalise if unresponsive to basic measures

Intraoperative floppy iris syndrome (IFIS) Not reversible on drug discontinuation; must inform ophthalmologist before any cataract surgery

Priapism (rare) Urological emergency; immediate discontinuation; may require intervention

Angioedema (rare) Discontinue immediately; manage airway; supportive care

Hepatitis (rare) Discontinue; monitor LFTs; specialist referral

Phase Parameters

Baseline Blood pressure (sitting and standing), heart rate, renal function, hepatic function, IPSS score (if used for BPH)

After initiation/dose change BP and orthostatic symptoms within 2–6 hours of first dose or dose increment; repeat monitoring for first 3–5 days of new dose

Long-term BP at each visit, orthostatic tolerance assessment, symptom review (LUTS if for BPH), LFTs periodically with prolonged use, renal function if on concurrent diuretics

• Cardura (Pfizer)

• Doxacard (Torrent)

• Doxazos (Cipla)

• Duracard (USV)

• Doxa (Micro Labs)

• Doxazosin (generic — multiple manufacturers)

Note: Extended-release (GITS) formulations available as Cardura XL. Some FDCs with finasteride available for BPH.

Strength Approximate Price (per 10 tablets)

• NLEM status: Not listed under NLEM 2022

• Government supply: Available through Jan Aushadhi at subsidised prices

• Private retail: Widely available

1. ALLHAT warning: Avoid doxazosin as first-line monotherapy for hypertension — ALLHAT trial demonstrated increased heart failure risk compared to chlorthalidone. Reserve as add-on therapy.

1. First-dose precaution: Always initiate at bedtime with patient in supine position; advise slow positional changes the following morning.

1. Dual benefit in men: Doxazosin is particularly useful when hypertension and symptomatic BPH co-exist — addresses both conditions with single agent.

1. Once-daily advantage: Longer half-life (~22 hours) compared to prazosin allows convenient once-daily dosing and smoother BP control.

1. IFIS alert: Even if discontinued, doxazosin can cause intraoperative floppy iris syndrome — always document alpha-blocker history before ophthalmic referral.

1. Extended-release option: GITS formulation provides more gradual drug release, potentially reducing first-dose effect — consider in patients highly susceptible to orthostatic symptoms.

doxazosin; alpha-blocker; hypertension; BPH; LUTS; PTSD-nightmares; once-daily; elderly-caution; first-dose-syncope; IFIS; renal-safe; Schedule-H

RxIndia v0.4 — 09 Jan 2025

• CDSCO-approved product inserts

• Indian Pharmacopoeia

• NFI 2021

• API Textbook of Medicine, 12th edition

• AIIMS Drug Formulary

• Indian Urology Association Guidelines for BPH Management

• ICMR Hypertension Management Guidelines

• Goodman & Gilman's The Pharmacological Basis of Therapeutics

• ALLHAT Collaborative Research Group (JAMA 2002) — for heart failure caution

• RCTs for PTSD off-label use (Rodgman et al.; clearly marked)