Classifications: nonnitrate vasodilator; antihypertensive;
Therapeutic: antihypertensive
; nonnitrate vasodilator
Prototype: Hydralazine
Pregnancy Category: C


50 mg injection


Potent, rapid-acting hypotensive agent with effects similar to those of nitrates. Acts directly on vascular smooth muscle to produce peripheral vasodilation, with consequently marked lowering of arterial BP that is associated with slight increase in heart rate, mild decrease in cardiac output, and moderate lowering of peripheral vascular resistance.

Therapeutic Effect

Effective antihypertensive agent used for rapid reduction of high blood pressure.


Short-term, rapid reduction of BP in hypertensive crises and for producing controlled hypotension during anesthesia to reduce bleeding.

Unlabeled Uses

Refractory CHF or acute MI.


Compensatory hypertension, as in atriovenous shunt or coarctation of aorta, and for control of hypotension in patients with inadequate cerebral circulation; pregnancy (category C), lactation.

Cautious Use

Hepatic insufficiency, hypothyroidism, severe renal impairment, hyponatremia, older adult patients with low vitamin B12 plasma levels or with Leber's optic atrophy.

Route & Dosage

Hypertensive Crisis
Adult: IV 0.3–0.5 mcg/kg/min (average 3 mcg/kg/min)
Child: IV 1 mcg/kg/min (average 3 mcg/kg/min) (max 5 mcg/kg/min)



PREPARE: Continuous: Dissolve each 50 mg in 2–3 mL of D5W. Further dilute in 250 mL D5W to yield 200 mcg/mL or 500 mL D5W to yield 100 mcg/mL. Lower concentrations may be desirable depending on patient weight. Following reconstitution, solutions usually have faint brownish tint; if solution is highly colored, do not use it. Promptly wrap container with aluminum foil or other opaque material to protect drug from light.  

ADMINISTER: Continuous: Administer by infusion pump or similar device that will allow precise measurement of flow rate required to lower BP. Give at the rate required to lower BP, usually between 0.5–10 mcg/kg/min. DO NOT exceed the maximum dose of 10 mcg/kg/min nor give this dose for longer than 10 min.  

INCOMPATIBILITIES Solution/additive: Amiodarone, propafenone. Y-site: Cisatracurium, haloperidol, levofloxacin.

  • Store reconstituted solutions and IV solution at 15°–30° C (59°–86° F) protected from light; stable for 24 h.

Adverse Effects (≥1%)

Body as a Whole: Diaphoresis, apprehension, restlessness, muscle twitching, retrosternal discomfort. Thiocyanate toxicity (profound hypotension, tinnitus, blurred vision, fatigue, metabolic acidosis, pink skin color, absence of reflexes, faint heart sounds, loss of consciousness). CV: Profound hypotension, palpitation, increase or transient lowering of pulse rate, bradycardia, tachycardia, ECG changes. GI: Nausea, retching, abdominal pain. Metabolic: Increase in serum creatinine, fall or rise in total plasma cobalamins. CNS: Headache, dizziness. Special Senses: Nasal stuffiness. Other: Irritation at infusion site.


No clinically significant interactions established.


Onset: Within 2 min. Duration: 1–10 min after infusion is terminated. Metabolism: Rapidly converted to cyanogen in erythrocytes and tissue, which is metabolized to thiocyanate in liver. Elimination: Excreted in urine primarily as thiocyanate. Half-Life: (thiocyanate): 2.7–7 d.

Nursing Implications

Assessment & Drug Effects

  • Monitor constantly to titrate IV infusion rate to BP response.
  • Relieve adverse effects by slowing IV rate or by stopping drug; minimize them by keeping patient supine.
  • Notify physician immediately if BP begins to rise after drug infusion rate is decreased or infusion is discontinued.
  • Monitor I&O.
  • Lab tests: Monitor blood thiocyanate level in patients receiving prolonged treatment or in patients with severe kidney dysfunction (levels usually are not allowed to exceed 10 mg/dL). Determine plasma cyanogen level following 1 or 2 d of therapy in patients with impaired liver function.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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