Boceprevir
Severe
Database
Drug interaction classified as: metabolism
Source: DDInter
Drug reference
Doxazosin
Alpha-1 adrenergic antagonist (quinazoline) · Antihypertensive, Benign Prostatic Hyperplasia Agent
START
1 mg PO at bedtime (first-dose hypotension risk)
TYPICAL MAX
16 mg/day (HTN); 8 mg/day (BPH or modified-release)
STOP IF
Syncope, severe orthostatic hypotension, or priapism
WATCH
Postural BP, dizziness; warn ophthalmologist (IFIS) before cataract surgery
CDSCO approvedSchedule HATC C02CA04
KDIGO 2024 + manufacturer label
- ONSET
- 2h · BP effect
- PEAK
- 3h · Cmax (IR)
- t½
- 22h · t½
- DURATION
- 1d · once-daily
EXCRETION
Mainly biliary/faecal; <5% renal unchanged
route + CYP
INTERACTIONS
3 major
SEVERE in our sources
PREGNANCY
Limited human data; use only if clearly needed (animal data without major teratogenicity).
FDA category + note
Top interactionssee all 9 →
- BoceprevirSevereDatabaseDDInter
- Sodium OxybateSevereDatabaseDDInter
- TizanidineSevereDatabaseDDInter
Available in India
8 branded formulations. Look up specific brands in the Drugs workspace.
Mechanism
Selective post-synaptic alpha-1 adrenoceptor blockade relaxes vascular smooth muscle (reducing peripheral resistance and BP) and relaxes prostatic/bladder-neck and urethral smooth muscle, improving urinary flow in BPH.
Indications
HypertensionBenign prostatic hyperplasia (LUTS)
Dosing
- Adult
- HTN/BPH: 1 mg PO once daily (bedtime), titrate slowly every 1–2 weeks; usual 1–8 mg/day. Modified-release: 4 mg once daily, max 8 mg/day.
- Pediatric
- Not established.
- Renal adjustment
- No dose adjustment required (not significantly renally excreted).
- Hepatic adjustment
- Caution; not recommended in severe hepatic impairment (extensively hepatically metabolised).
- Geriatric
- Start 1 mg; greater orthostatic-hypotension risk.
- Max dose
- 16 mg/day (immediate-release, hypertension); 8 mg/day (BPH / modified-release)
Pharmacokinetics
Onset
1–2 h (BP); 1–2 weeks for full antihypertensive effect
Peak effect
2–3 h (immediate-release)
Duration
~24 h
Half-life
~22 h
Bioavailability
~65%
Protein binding
~98%
Metabolism
Extensive hepatic (CYP3A4, O-demethylation/hydroxylation)
Excretion
Mainly biliary/faecal; <5% renal unchanged
Contraindications
- Hypersensitivity to quinazolines (prazosin, terazosin, doxazosin)
- History of postural hypotension/syncope with alpha-blockers
- Concomitant PDE-5 inhibitor with caution (additive hypotension)
Side effects
Common
DizzinessHeadacheFatiguePostural hypotensionPeripheral oedemaSomnolence
Serious
- First-dose syncope
- Severe orthostatic hypotension
- Priapism
- Intraoperative floppy iris syndrome
Pregnancy & lactation
Pregnancy
Limited human data; use only if clearly needed (animal data without major teratogenicity).
Lactation
Excreted in animal milk; caution — limited human data.
Drug interactions
Sodium Oxybate
Severe
Database
.
Source: DDInter
Tizanidine
Severe
Database
Clinical effect not specified
Source: DDInter
Acebutolol
Moderate
Database
Increased antihypertensive effect.
This combination is often used to achieve better blood pressure control and manage reflex tachycardia from alpha-1 blockers.
Source: DDInter
Betaxolol
Moderate
Database
Increased antihypertensive effect.
This combination is often used to achieve better blood pressure control and manage reflex tachycardia from alpha-1 blockers.
Source: DDInter
Carteolol
Moderate
Database
Increased antihypertensive effect.
This combination is often used to achieve better blood pressure control and manage reflex tachycardia from alpha-1 blockers.
Source: DDInter
Carvedilol
Moderate
Database
Increased antihypertensive effect.
This combination is often used to achieve better blood pressure control and manage reflex tachycardia from alpha-1 blockers.
Source: DDInter
Metoprolol
Moderate
Database
Increased antihypertensive effect.
This combination is often used to achieve better blood pressure control and manage reflex tachycardia from alpha-1 blockers.
Source: DDInter
Nebivolol
Moderate
Database
Increased antihypertensive effect.
This combination is often used to achieve better blood pressure control and manage reflex tachycardia from alpha-1 blockers.
Source: DDInter
3 additional low-confidence interactions hidden — those rows lack a documented mechanism or management plan in our sources.
Related guidelines
Ask House about Doxazosin
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Sources: KD Tripathi 7e, Goodman & Gilman 14e, Harrison 22e, BNF·Verified: 2026-05-20 · House clinical team·Cockpit curated: 2026-05-20