Hydralazine hydrochloride (Apresoline)
Pregnancy Category: C
Antihypertensive, direct action on vascular smooth muscle
Exerts a direct vasodilating effect on vascular smooth muscle. Also alters cellular calcium metabolism that interferes with calcium movement within the vascular smooth muscle responsible for initiating or maintaining contraction. Preferentially dilates arterioles compared with veins; this minimizes postural hypotension and increases CO. Increases renin activity in the kidney, leading to an increase in angiotensin II, which then causes stimulation of aldosterone and thus sodium reabsorption. Because there is a reflex increase in cardiac function, hydralazine is commonly used with drugs that inhibit sympathetic activity (e.g., beta blockers, clonidine, methyldopa). Rapidly absorbed after PO use. Food increases bioavailability of the drug.
PO: Onset: 45 min;
peak plasma level: 1-2 hr;
duration: 3-8 hr.
1/2: 3-7 hr.
IM: Onset: 10-30 min;
peak plasma level: 1 hr;
duration: 2-4 hr.
IV: Onset: 10-20 min;
maximum effect: 10-80 min;
duration: 2-4 hr. Metabolized in the liver and excreted through the kidney (2%-5% unchanged after PO use and 11%-14% unchanged after IV administration).
PO: In combination with other drugs for essential hypertension.
Parenteral: Severe essential hypertension when PO use is not possible or when there is an urgent need to lower BP. Hydralazine is the drug of choice for eclampsia.
Investigational: To reduce afterload in CHF, severe aortic insufficiency, and after valve replacement.
Coronary artery disease, angina pectoris, advanced renal disease (as in chronic renal hypertension), rheumatic heart disease (e.g., mitral valvular) and chronic glomerulonephritis.
Use with caution in stroke clients, in those with pulmonary hypertension, during lactation, in clients with advanced renal disease, and in clients with tartrazine sensitivity. Safety and efficacy have not been established in children. Geriatric clients may be more sensitive to the hypotensive and hypothermic effects of hydralazine; also, a decrease in dose may be necessary in these clients due to age-related decreases in renal function.
CV: Orthostatic hypotension, hypotension,
MI angina pectoris, palpitations, paradoxical pressor reaction, tachycardia.
CNS: Headache, dizziness, psychoses, tremors, depression, anxiety, disorientation.
GI: N&V, diarrhea, anorexia, constipation, paralytic ileus.
Allergic: Rash, urticaria, fever, chills, arthralgia, pruritus, eosinophilia. Rarely, hepatitis, obstructive jaundice.
Hematologic: Decrease in hemoglobin and RBCs, purpura, agranulocytosis, leukopenia.
Other: Peripheral neuritis (par-esthesias, numbness, tingling), dyspnea, impotence, nasal congestion, edema, muscle cramps, lacrimation, flushing, conjunctivitis, difficulty in urination, lupus-like syndrome, lymphadenopathy, splenomegaly. Side effects are less severe when dosage is increased slowly.
NOTE: Hydralazine may cause symptoms resembling SLE (e.g., arthralgia, dermatoses, fever, splenomegaly, glomerulonephritis). Residual effects may persist for several years and long-term treatment with steroids may be necessary.
Symptoms: Hypotension, tachycardia, skin flushing, headache. Also, myocardial ischemia,
cardiac arrhythmias, MI, and severe shock.
Treatment: If the CV status is stable, induce vomiting or perform gastric lavage followed by activated charcoal. Treat shock with volume expanders, without vasopressors; if a vasopressor is necessary, one should be used that is least likely to cause or aggravate tachycardia and cardiac arrhythmias. Monitor renal function.
Beta-adrenergic blocking agents /
Effect of both drugs
Effect of hydralazine
Methotrimeprazine / Additive hypotensive effect
Procainamide / Additive hypotensive effect
Quinidine / Additive hypotensive effect
Risk of tachycardia and angina
Injection: 20 mg/mL;
Tablet: 10 mg, 25 mg, 50 mg, 100 mg
Adult, initial: 10 mg q.i.d for 2-4 days;
then, increase to 25 mg q.i.d. for rest of first week. For second and following weeks, increase to 50 mg q.i.d.
Maintenance: individualized to lowest effective dose; do not exceed a maximum daily dose of 300 mg.
Pediatric, initial: 0.75 mg/kg/day (25 mg/m
2/day) in two to four divided doses; dosage may be increased gradually up to 7.5 mg/kg/day (or 300 mg/day). Food increases the bioavailability of the drug.
Adults, usual: 20-40 mg, repeated as necessary. BP may fall within 5-10 min, with maximum response in 10-80 min. Usually switch to PO medication in 1-2 days. Decrease dosage in clients with renal damage.
Pediatric: 0.1-0.2 mg/kg q 4-6 hr as needed.
5-10 mg q 20 min as an IV bolus. If no effect after 20 mg, another drug should be tried.