Doxazosin Uses, Dosage, Side Effects & Warnings | DrugsAtlas
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DRUG NAME: Doxazosin
Therapeutic Class: Antihypertensive
Subclass: Alpha-1 Adrenergic Receptor Blocker
Specialty: General Medicine / Cardiology / Urology
Schedule (India): Schedule H
Route(s): Oral
Subclass: Alpha-1 Adrenergic Receptor Blocker
Specialty: General Medicine / Cardiology / Urology
Schedule (India): Schedule H
Route(s): Oral
Formulations Available in India:
• Doxazosin immediate-release (IR) tablets: 1 mg, 2 mg, 4 mg
• Doxazosin extended release (ER) tablets: 4 mg, 8 mg
• Doxazosin extended release (ER) tablets: 4 mg, 8 mg
INDICATIONS + DOSING — FOR CLINICIAN USE ONLY
Primary Indications (Approved / Standard in India):
1. Hypertension (Monotherapy or Add-on Therapy)
| Parameter | Immediate-Release (IR) | Extended-Release (ER) |
| Starting dose | 1 mg once daily at bedtime | 4 mg once daily (morning with breakfast) |
| Titration | Increase by 1–2 mg at 1–2 week intervals | May increase to 8 mg after 3–4 weeks |
| Usual maintenance dose | 2–4 mg once daily | 4–8 mg once daily |
| Maximum dose | 16 mg/day | 8 mg/day |
Clinical Notes:
- Administer first dose of IR at bedtime to minimise first-dose hypotension
- ER tablets are NOT bioequivalent to IR tablets; do not substitute mg-for-mg
- ER tablets must be swallowed whole; do not crush or chew
2. Benign Prostatic Hyperplasia (BPH) — Symptomatic Relief
| Parameter | Immediate-Release (IR) | Extended-Release (ER) |
| Starting dose | 1 mg once daily at bedtime | 4 mg once daily |
| Titration | Increase to 2 mg, then 4 mg at weekly intervals as tolerated | May increase to 8 mg after 3–4 weeks |
| Usual maintenance dose | 2–4 mg once daily | 4–8 mg once daily |
| Maximum dose | 8 mg/day | 8 mg/day |
Clinical Notes:
- Improvement in urinary flow and symptoms typically seen within 1–2 weeks
- Full therapeutic response may require 4–6 weeks
- Particularly useful when hypertension coexists with BPH
- Does not reduce prostate size; symptomatic relief only
Secondary Indications — Adults (Off-label, if any):
| Indication | Dose | Evidence Basis | Notes |
| Raynaud’s Phenomenon (OFF-LABEL) | Starting: 1 mg/day; Titration: increase to 2–4 mg/day over 2–4 weeks | Small RCTs; Indian specialist practice | Specialist only; use in refractory cases unresponsive to calcium channel blockers |
PAEDIATRIC DOSING (Specialist Only)
Primary Indications:
Not approved for routine paediatric use in India.
Secondary Indications — Paediatric Doses (Off-label):
| Indication | Recommendation |
| Paediatric Hypertension (OFF-LABEL) | NOT RECOMMENDED below 18 years |
Statement: Use is not recommended in children and adolescents except under paediatric cardiologist/nephrologist supervision. Limited safety and efficacy data exist. Prefer agents with established paediatric evidence (e.g., amlodipine, enalapril).
RENAL ADJUSTMENT
| Renal Function | Recommendation |
| Mild to moderate impairment (eGFR ≥30 mL/min/1.73 m²) | No dosage adjustment required |
| Severe impairment (eGFR <30 mL/min/1.73 m²) | Use with caution; monitor BP closely for hypotension |
| Haemodialysis | Not significantly dialysed; no supplemental dose required |
HEPATIC ADJUSTMENT
| Severity | Recommendation |
| Mild impairment (Child-Pugh A) | Start with 1 mg/day; titrate cautiously |
| Moderate impairment (Child-Pugh B) | Use with caution; lower starting dose; slow titration; close monitoring |
| Severe impairment (Child-Pugh C) | Avoid use — increased systemic exposure and hypotension risk |
CONTRAINDICATIONS
- Known hypersensitivity to doxazosin, other quinazolines (e.g., prazosin, terazosin), or any excipient
- History of orthostatic hypotension
- Severe hepatic impairment
- Monotherapy in patients with overflow bladder or anuria (for BPH indication)
- Lactation (manufacturer contraindication)
CAUTIONS
- Volume-depleted patients (diuretic therapy, dialysis, dietary salt restriction) — increased first-dose hypotension risk
- Elderly patients — higher susceptibility to orthostatic hypotension and falls
- Congestive heart failure with low systemic vascular resistance
- Concurrent use of other antihypertensives or PDE-5 inhibitors
- Planned cataract surgery — risk of Intraoperative Floppy Iris Syndrome (IFIS); inform ophthalmologist prior to surgery
- Priapism risk (rare) — advise patients to seek urgent care if prolonged erection occurs
PREGNANCY
| Parameter | Details |
| Safety category | Not formally classified by CDSCO; limited human data |
| Overall recommendation | Avoid unless essential; use only if potential benefit outweighs risk |
| Specialist input | Recommended before initiating |
| Preferred alternatives | Labetalol, methyldopa, nifedipine (for hypertension in pregnancy) |
| Fetal monitoring | Growth surveillance; monitor for neonatal hypotension if used near term |
LACTATION
| Parameter | Details |
| Compatibility | Not recommended during breastfeeding |
| Excretion in milk | Detected in animal milk; human data limited |
| Preferred alternatives | Labetalol, propranolol, nifedipine (for hypertension) |
| Infant monitoring | If unavoidable: monitor for hypotonia, poor feeding, lethargy |
ELDERLY
- Starting dose: 0.5–1 mg/day (IR) or 4 mg/day (ER); use lowest effective dose
- Titration: Slow; increase at 2-week intervals minimum
- Risks: Elevated risk of first-dose syncope, orthostatic hypotension, and falls
- Administration: Give IR dose at bedtime
- Monitoring: Regularly assess standing blood pressure, hydration status, renal function
MAJOR DRUG INTERACTIONS
| Interacting Drug | Mechanism | Clinical Action |
| Phosphodiesterase-5 inhibitors (sildenafil, tadalafil, vardenafil) | Additive vasodilation | Avoid concurrent initiation; if combined, separate dosing by at least 6 hours; patient should be stable on alpha-blocker first |
| Strong CYP3A4 inhibitors (ketoconazole, itraconazole, ritonavir) | Increased doxazosin plasma levels | Avoid combination or reduce doxazosin dose; monitor closely for hypotension |
| Other alpha-blockers (prazosin, terazosin, tamsulosin) | Additive alpha-blockade | Avoid concurrent use |
MODERATE DRUG INTERACTIONS
| Interacting Drug | Effect | Clinical Action |
| Other antihypertensives (beta-blockers, ACE inhibitors, ARBs, diuretics) | Additive BP-lowering | Initiate doxazosin cautiously; monitor BP closely; dose adjustment may be needed |
| NSAIDs (ibuprofen, diclofenac, naproxen) | May reduce antihypertensive effect | Monitor BP; adjust antihypertensive if required |
| Alpha-blocking antipsychotics (chlorpromazine, risperidone) | Additive hypotensive effect | Close monitoring; use lower doses |
| Alcohol | Potentiates hypotension | Advise patients to limit alcohol intake |
COMMON ADVERSE EFFECTS
- Dizziness
- Headache
- Fatigue / asthenia
- Postural hypotension
- Peripheral oedema
- Nasal congestion / rhinitis
- Palpitations
- Nausea
SERIOUS ADVERSE EFFECTS
| Adverse Effect | Action Required |
| Syncope (especially first-dose) | Immediate medical attention; reassess therapy |
| Intraoperative Floppy Iris Syndrome (IFIS) | Inform ophthalmologist; may complicate cataract surgery |
| Angioedema (rare) | Discontinue immediately; manage as allergic emergency |
| Priapism (rare) | Urgent urological referral |
| Hepatic dysfunction (very rare) | Discontinue if jaundice or elevated transaminases develop |
MONITORING REQUIREMENTS
| Phase | Parameters |
| Baseline | Blood pressure (supine and standing); liver function tests (if hepatic history); renal function |
| After initiation / dose change | BP monitoring 2–6 hours after first dose and after each dose increment; assess for dizziness/syncope |
| Long-term | Periodic BP assessment; orthostatic symptoms; hepatic function if prolonged use |
BRANDS AVAILABLE IN INDIA
- Cardura (Pfizer)
- Doxacard (Zydus Cadila)
- Doxolin (Lupin)
- Doxyure (Dr. Reddy’s)
- Doxagon (Cipla)
- Doxatrol (Sun Pharma)
- Multiple generics available
Fixed Dose Combinations (FDCs): Doxazosin-based FDCs are not widely marketed in India.
PRICE RANGE (INR)
| Formulation | Approximate Price (per tablet) |
| IR 1 mg | ₹2–5 |
| IR 2 mg | ₹4–8 |
| IR 4 mg | ₹6–12 |
| ER 4 mg | ₹12–20 |
| ER 8 mg | ₹18–30 |
Note: Not included in NLEM 2022; not price-controlled under NPPA. Costs vary by brand and region.
CLINICAL PEARLS
- Always administer the first IR dose at bedtime to minimise first-dose syncope risk
- IR and ER formulations are NOT interchangeable mg-for-mg due to different bioavailability
- Excellent choice in male patients with coexisting hypertension and BPH — addresses both conditions
- Not all patients tolerate maximum doses; individualise titration based on response and tolerability
- Alert ophthalmologist before cataract surgery if patient has ever used doxazosin (IFIS risk persists even after discontinuation)
- Reassess need in BPH after 6 months; consider step-down if symptoms well controlled
TAGS
doxazosin; alpha-blocker; hypertension; BPH; lower urinary tract symptoms; first-dose hypotension; elderly-caution; renal-safe; IFIS; cardiology; urology
VERSION
RxIndia v1.0 — 14 Feb 2026
REFERENCES
- CDSCO Drug Approval Database
- Indian Pharmacopoeia / National Formulary of India 2021
- API Textbook of Medicine (11th Edition)
- AIIMS Hospital Formulary
- NLEM 2022
- ICMR Guidelines on Management of Hypertension 2023
- Harrison’s Principles of Internal Medicine (21st Edition)
- Manufacturer Product Information (Cardura — Pfizer India)
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Clinical Responsibility
This platform is designed strictly for healthcare professionals. Data provided is synthesized from authoritative pharmacological sources and clinical registries. Do not use for consumer medical decisions. Always verify critical dosing and contraindications with official institutional protocols and peer-reviewed journals.
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