Drug reference

Hydralazine

Direct arterial vasodilator · Antihypertensive

Also known as Hydralazine hydrochloride

START

Oral 25 mg BID–QID titrate (with beta-blocker + diuretic for reflex effects); pregnancy/severe HTN IV 5–10 mg, repeat

TYPICAL MAX

300 mg/day oral (limit to reduce lupus risk; ≤100 mg/day in slow acetylators)

STOP IF

Drug-induced lupus (arthralgia, rash, +ANA/anti-histone), severe ischaemia, blood dyscrasia

WATCH

ANA/lupus symptoms (esp. >100–200 mg/day, slow acetylators), reflex tachycardia/fluid retention (combine therapy), BP

CDSCO approvedATC C02DB02

Dose laddermg/d

Renal dose adjustmenteGFR mL/min/1.73m²

KDIGO 2024 + manufacturer label

Pharmacokineticsplasma · t hours

ONSET: 30min · oral onset
PEAK: 1.5h · Cmax
t½: 4h · plasma t½
DURATION: 7h · oral effect

EXCRETION

Hepatic N-acetylation; renal metabolites

route + CYP

INTERACTIONS

5 major

incl. contraindicated

PREGNANCY

Used in pregnancy for severe hypertension/pre-eclampsia (IV) under monitoring — established obstetric agent

FDA category + note

Top interactionssee all 6 →

DihydropyridinesContraindicatedTextbookKDT 7e · p571
PrazosinContraindicatedTextbookKDT 7e · p571
Mao InhibitorsSevereDatabaseKimi deep-research + Cla
Other AntihypertensivesSevereDatabaseKimi deep-research + Cla

Available in India

6 branded formulations and 8 fixed-dose combinations. Look up specific brands in the Drugs workspace.

Mechanism

Direct relaxation of arteriolar smooth muscle (interferes with calcium release/IP3, increases NO/cGMP) reducing systemic vascular resistance and afterload; reflex tachycardia and fluid retention often necessitate combination therapy.

Indications

Hypertension (adjunct, esp. resistant; with beta-blocker + diuretic)Heart failure (with isosorbide dinitrate — esp. African-American patients / ACEi-intolerant)Hypertensive emergencies in pregnancy (IV — pre-eclampsia)

Dosing

Adult: Oral: 25 mg BID–QID, titrate (usual ≤200 mg/day; max 300 mg/day — higher → lupus risk). IV (severe HTN/pregnancy): 5–10 mg slow IV, repeat every 20–30 min as needed.
Pediatric: 0.75–1 mg/kg/day divided (specialist).
Renal adjustment: Severe impairment: extend dosing interval (reduced clearance).
Hepatic adjustment: Reduce dose (reduced first-pass/clearance).
Geriatric: Lower dose; orthostasis.
Max dose: 300 mg/day oral (lupus risk rises >100–200 mg/day, esp. slow acetylators)

Pharmacokinetics

Onset

Oral ~20–30 min; IV 5–20 min

Peak effect

Oral 1–2 h; IV ~10–80 min

Duration

Oral ~6–8 h; IV 2–6 h

Half-life

~3–7 h (acetylator-status dependent)

Bioavailability

Oral ~30–50% (genetic acetylation polymorphism)

Protein binding

~87%

Metabolism

Hepatic N-acetylation (fast vs slow acetylators) + hydroxylation

Excretion

Renal (mostly metabolites)

Contraindications

Coronary artery disease / mitral valve rheumatic heart disease (relative — reflex ischaemia)
Systemic lupus erythematosus (idiopathic) — relative
Dissecting aortic aneurysm
Hypersensitivity to hydralazine