| HYDRALAZINE HYDROCHLORIDE
Classifications: nonnitrate vasodilator; antihypertensive; Therapeutic: antihypertensive
Pregnancy Category: C
10 mg, 25 mg, 50 mg, 100 mg tablets; 20 mg/mL vial
Reduces BP mainly by direct effect on vascular smooth muscles of arterial-resistance vessels, resulting in vasodilation.
Has little effect on venous-capacitance vessels. Hypotensive effect may be limited by sympathetic reflexes that increase
heart rate, stroke volume, and cardiac output.
Reduces BP with diastolic response often being greater than systolic response. Vasodilation reduces peripheral resistance
and substantially improves cardiac output, and renal and cerebral blood flow.
Most commonly in stepped-care approach to treat moderate to severe hypertension. Also in early malignant hypertension and
resistant hypertension that persists after sympathectomy.
Conjunctively with cardiac glycosides and other vasodilators in short-term treatment of acute CHF; unexplained pulmonary
Coronary artery disease, mitral valvular rheumatic heart disease, MI, tachycardia, SLE; pregnancy (category C).
Cerebrovascular accident, advanced renal impairment, coronary heart disease, renal disease; renal failure; use with MAO INHIBITORS.
Route & Dosage
Adult: PO 1050 mg q.i.d. IM 1050 mg q46h IV 1020 mg q46h, may increase to 40 mg
Geriatric: PO Start with 10 mg 23 times/d
Child: PO 37.5 mg/kg/d in 4 divided doses IV/IM 0.10.2 mg/kg in divided doses (max 20 mg)
Clcr1050 mL/min: dose q8h
- Give with food; bioavailability is increased by taking it with food.
- Discontinue gradually to avoid sudden rise in BP and acute heart failure.
- Inform patients of the dangers of abrupt withdrawal.
- Give deep into a large muscle.
PREPARE: Direct: Give undiluted. Use immediately after being drawn into syringe. Do not add to IV solutions.
ADMINISTER: Direct: Give each 10 mg or fraction thereof over 1 min.
INCOMPATIBILITIES Solution/additive: Aminophylline, ampicillin, chlorothiazide, edetate calcium disodium, ethacrynate, hydrocortisone, mephentermine, methohexital, nitroglycerin, phenobarbital, verapamil, D5W. Y-site: Aminophylline, ampicillin, diazoxide, furosemide.
- Store at 15°30° C (59°86° F) in tight, light-resistant containers unless otherwise directed.
Adverse Effects (≥1%)Body as a Whole:
Hypersensitivity (rash, urticaria, pruritus, fever, chills, arthralgia
, eosinophilia, cholangitis, hepatitis
jaundice). CNS: Headache,
dizziness, tremors. CV: Palpitation,
flushing, paradoxical pressor response. Overdose: arrhythmia, shock. Special Senses:
Anorexia, nausea, vomiting, diarrhea
, abdominal pain, paralytic ileus. Urogenital:
Difficulty in urination, glomerulonephritis. Hematologic:
Nasal congestion, muscle cramps, SLE-like syndrome
, fixed drug eruption, edema.
Diagnostic Test Interference
Positive direct Coombs' tests in patients with hydralazine-induced SLE. Hydralazine interferes with urinary 17-OHCS determinations (modified Glenn-Nelson technique).
InteractionsDrug: beta blockers
and other antihypertensive agents
compound hypotensive effects.
Readily absorbed from GI tract. Onset:
2030 min. Peak:
2 h. Duration:
26 h. Distribution:
Crosses placenta; distributed into breast milk. Metabolism:
In liver. Elimination:
90% in urine; 10% in feces. Half-Life:
Assessment & Drug Effects
- Lab tests: Determine antinuclear antibody titer before initiation of therapy and periodically during prolonged therapy.
- Make baseline and periodic determinations of BUN, creatinine clearance, uric acid, serum potassium, blood glucose, and ECG.
- Monitor for S&S of SLE, especially with prolonged therapy.
- Monitor BP and HR closely. Check every 5 min until it is stabilized at desired level, then every 15 min thereafter throughout
- Monitor I&O when drug is given parenterally and in those with renal dysfunction.
Patient & Family Education
- Monitor weight, check for edema, and report weight gain to physician.
- Note: Some patients experience headache and palpitations within 24 h after first PO dose; symptoms usually subside spontaneously.
- Make position changes slowly and avoid standing still, hot baths/showers, strenuous exercise, and excessive alcohol intake.
- Do not drive or engage in other potentially hazardous activities until response to drug is known.