Moderate to severe hypertension (with a diuretic).
HF unresponsive to conventional therapy with digoxin and diuretics.
Direct-acting peripheral arteriolar vasodilator.
Lowering of BP in hypertensive patients and decreased afterload in patients with HF.
Absorption: Rapidly absorbed following oral administration; well absorbed from IM sites.
Distribution: Widely distributed. Crosses the placenta; enters breast milk in minimal concentrations.
Metabolism and Excretion: Mostly metabolized by the GI mucosa and liver by N-acetyltransferase (rate of acetylation is genetically determined [slow acetylators have ↑ hydralazine levels and ↑ risk of toxicity; fast acetylators have ↓ hydralazine levels and ↓ response]).
Half-life: 2–8 hr.
TIME/ACTION PROFILE (antihypertensive effect)
|PO||45 min||2 hr||2–4 hr|
|IM||10–30 min||1 hr||3–8 hr|
|IV||5–20 min||15–30 min||2–6 hr|
Use Cautiously in:
CV: tachycardia, angina, arrhythmias, edema, orthostatic hypotension
GI: diarrhea, nausea, vomiting
MS: arthralgias, arthritis
Neuro: dizziness, drowsiness, headache, peripheral neuropathy
Misc: drug-induced lupus syndrome
* CAPITALS indicate life-threatening.
Underline indicate most frequent.
PO (Adults): Hypertension– 10 mg 4 times daily initially. After 2–4 days may ↑ to 25 mg 4 times daily for the rest of the 1st wk; may then ↑ to 50 mg 4 times daily (up to 300 mg/day). Once maintenance dose is established, twice-daily dosing may be used. HF– 25–37.5 mg 4 times daily; may be ↑ up to 300 mg/day in 3–4 divided doses.
PO (Children >1 mo): 0.75–1 mg/kg/day in 2–4 divided doses (max = 25 mg/dose) initially; may ↑ gradually to 5 mg/kg/day in infants and 7.5 mg/kg/day in children (max = 200 mg/day) in 2–4 divided doses.
IM IV (Adults): Hypertension– 5–40 mg repeated as needed. Eclampsia– 5 mg every 15–20 min; if no response after a total of 20 mg, consider an alternative agent.
IM IV (Children >1 mo): 0.1–0.2 mg/kg/dose every 4–6 hr (max = 20 mg/dose) as needed, up to 1.7–3.5 mg/kg/day in 4–6 divided doses.
Tablets: 10 mg, 25 mg, 50 mg, 100 mg
Injection: 20 mg/mL
In Combination with: isosorbide dinitrate (BiDil). See combination drugs.
Monitor BP and pulse frequently during initial dose adjustment and periodically during therapy. About 50–65% of Caucasians, Black, South Indians, and Mexicans are slow acetylators at risk for toxicity, while 80–90% of Eskimos, Japanese, and Chinese are rapid acetylators at risk for decreased levels and treatment failure.
Lab Test Considerations:
Monitor CBC, electrolytes, LE cell prep, and ANA titer prior to and periodically during prolonged therapy.
Do not confuse hydralazine with hydroxyzine or hydrochlorothiazide.
Administer with meals consistently to enhance absorption.
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