Medically reviewed on September 10, 2018
(hye DRAL a zeen)
- Hydralazine HCl
- Hydralazine Hydrochloride
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Solution, Injection, as hydrochloride:
Generic: 20 mg/mL (1 mL)
Tablet, Oral, as hydrochloride:
Generic: 10 mg, 25 mg, 50 mg, 100 mg
Direct vasodilation of arterioles (with little effect on veins) with decreased systemic resistance
Oral: Rapidly absorbed
Hepatically acetylated; extensive first-pass effect (oral)
Urine (as metabolites)
Onset of Action
IV: 10 to 80 minutes
Time to Peak
Plasma: Oral: 1 to 2 hours
Duration of Action
IM, IV: Up to 12 hours (Marik 2007); Note: Duration may vary depending on acetylator status of patient. Hypotension due to hydralazine may last longer even though the circulating half-life is much shorter (Marik, 2007; O’Malley, 1975).
3 to 7 hours
Special Populations Note
Slow acetylators: Patients will generally have higher plasma levels of hydralazine and require lower doses to maintain control of BP.
Use: Labeled Indications
Hypertension: Management of moderate to severe hypertension. Note: Not recommended for the initial treatment of hypertension (ACC/AHA [Whelton 2017]).
Off Label Uses
Heart failure with reduced ejection fraction (HFrEF) (intolerance to an ACE inhibitor or angiotensin receptor blocker)
Data from a randomized, double-blind trial comparing enalapril and hydralazine plus isosorbide dinitrate in patients with chronic heart failure supports the use of hydralazine (in combination with isosorbide dinitrate) in patients with intolerance to ACE inhibitor therapy [Cohn 1991].
Based on the American College of Cardiology Foundation/American Heart Association (ACCF/AHA) guidelines for the management of heart failure, hydralazine (in combination with isosorbide dinitrate) is effective and recommended for patients with HFrEF who do not tolerate an ACE inhibitor or an ARB.
Heart failure with reduced ejection fraction (HFrEF) NYHA Class III-IV (African-American [self-identified] patients)
Data from a randomized, double-blind, placebo-controlled trial in black patients with NYHA class III or IV heart failure supports the use of hydralazine (in combination with isosorbide dinitrate and standard therapy for heart failure) for the management of black patients with this condition [Taylor 2004].
Based on the American College of Cardiology Foundation/American Heart Association (ACCF/AHA) guidelines for the management of heart failure, hydralazine (in combination with isosorbide dinitrate) is effective and recommended for self-identified African-American patients with NYHA Class III-IV HFrEF remaining symptomatic despite optimal guideline directed medical therapy.
Hypertensive emergency in pregnancy
Based on the American College of Obstetricians and Gynecologists (ACOG) guidelines on the management of hypertension in pregnancy, the use of hydralazine is effective and recommended as a treatment option in pregnant and postpartum patients who are experiencing acute onset, severe hypertension with preeclampsia or eclampsia [ACOG 2017].
Additional Off-Label Uses
Hypersensitivity to hydralazine or any component of the formulation; coronary artery disease; mitral valve rheumatic heart disease
Hypertension (alternative agent): Oral: Initial: 10 to 25 mg 2 to 4 times daily; titrate as needed up to maximum dose of 300 mg daily in 2 to 4 divided doses. Usual dosage range: 100 to 200 mg daily in 2 to 3 divided doses (ACC/AHA [Whelton 2017]).
Heart failure (off-label use): Oral: Initial dose: 25 to 50 mg 3 or 4 times daily; use in combination with isosorbide dinitrate; maximum dose: 300 mg daily in divided doses (ACCF/AHA [Yancy 2013])
Hypertensive emergency (off-label dose): Note: Use is generally not recommended due to unpredictable and prolonged antihypertensive effects (Marik 2007): IM, IV: 10 to 20 mg every 4 to 6 hours as needed (Rhoney 2009)
Hypertensive emergency in pregnancy (systolic BP ≥160 mm Hg or diastolic BP ≥110 mm Hg) (off-label dose): IM, IV: Initial: 5 or 10 mg; may repeat dose in 20 to 40 minutes with 5 to 10 mg if blood pressure continues to exceed thresholds (ACOG 2017; Magee 2014; Too 2013). Also refer to administration protocols developed by the American College of Obstetricians and Gynecologists (ACOG 2017). A maximum total cumulative dose of 20 mg (IV) or 30 mg (IM) is recommended (Magee 2014). Note: After the initial dose, may initiate a continuous infusion of 0.5 to 10 mg/hour instead of intermittent dosing (Magee 2014).
Perioperative hypertension (off-label dose): IV: 3 to 20 mg every 20 to 60 minutes as needed (Varon 2008). Note: The lower end of the dosage range is preferred in the immediate perioperative period and in patients with renal failure. The use of hydralazine in this setting especially in patients with ischemic heart disease, aortic dissection, or an intracranial process is best avoided due to unpredictable and prolonged antihypertensive effects (Lien 2012; Varon 2008).
Refer to adult dosing.
Children and Adolescents: Note: Individualize dose; titrate gradually to patient response.
Hypertension, chronic: Oral: Initial: 0.75 mg/kg/day in 2 to 4 divided doses, maximum initial dose: 10 mg/dose; may increase gradually over 3 to 4 weeks up to a maximum of 7.5 mg/kg/day in 2 to 4 divided doses not to exceed 200 mg/day (NHBPEP 2004; NHLBI 2012; Park 2014)
Hypertensive emergency/urgency: IM, IV: Initial: 0.1 to 0.2 mg/kg/dose every 4 to 6 hours; increase as required to suggested usual range: 0.2 to 0.6 mg/kg/dose every 4 to 6 hours as needed; maximum dose: 20 mg/dose (NHBPEP 2004; Park 2014; Thomas 2011); manufacturer labeling suggests a dose range of 1.7 to 3.5 mg/kg/day divided in 4 to 6 doses
Dosing: Renal Impairment
There are no dosage adjustments provided in the manufacturer's labeling; however, the following adjustments have been recommended (Aronoff 2007):
Children and Adolescents: Note: Renally adjusted dose recommendations are based on doses: Oral: 0.75 to 1 mg/kg/day divided every 6 to 12 hours; IV: 0.1 to 0.2 mg/kg/dose every 6 hours:
GFR >50 mL/minute/1.73 m2: No adjustment necessary
GFR 10 to 50 mL/minute/1.73 m2: Administer every 8 hours
GFR <10 mL/minute/1.73 m2: Administer every 12 to 24 hours
Intermittent hemodialysis: Administer every 12 to 24 hours
Peritoneal dialysis: Administer every 12 to 24 hours
Continuous renal replacement therapy: Administer every 8 hours
Adults: Note: Renally adjusted dose recommendations are based on doses of 25 to 50 mg every 8 hours:
GFR ≥10 mL/minute: Administer every 8 hours.
GFR <10 mL/minute: Administer every 8 to 16 hours
Intermittent hemodialysis: Dose after dialysis
Peritoneal dialysis: Administer every 8 to 16 hours
Continuous renal replacement therapy: Administer every 8 hours
Dosing: Hepatic Impairment
There are no dosage adjustments provided in the manufacturer's labeling. However, hydralazine undergoes extensive hepatic metabolism.
4 mg/mL Oral Suspension (ASHP standard concentration) (ASHP 2017)
A 4 mg/mL oral suspension may be made with tablets and a 1:1 mixture of Ora-Sweet SF and Ora-Plus. Crush four 100 mg tablets in a mortar and reduce to a fine powder. Add 15 mL of the vehicle and mix to a uniform paste; mix while adding the vehicle in incremental proportions to almost 100 mL; transfer to a calibrated bottle, rinse mortar with vehicle, and add quantity of vehicle sufficient to make 100 mL. Label “shake well”, “protect from light”, “store in a refrigerator.” Stable for 2 days when stored in amber plastic prescription bottles in the dark and refrigerated (Allen 1998).
Note: Stability reduced to 24 hours if Ora-Sweet is substituted for Ora-Sweet SF.Allen LV Jr, Erickson MA 3rd. Stability of alprazolam, chloroquine phosphate, cisapride, enalapril maleate, and hydralazine hydrochloride in extemporaneously compounded oral liquids. Am J Health-Syst Pharm. 1998;55(18):1915-1920.9784772
Oral: Administer without regard to meals. However, food enhances bioavailability; administer consistently with regard to meals.
Injection: Response may be delayed and unpredictable in some patients; titrate cautiously to response.
IM: Administer undiluted as IM injection.
IV: Administer undiluted as slow IV push; maximum rate in children: 5 mg/minute (Klaus 1989). May also administer as a continuous infusion; refer to indication-specific infusion rates in dosing for detailed recommendations.
Tablets: Store at 15ºC to 30ºC (59ºF to 86ºF).
Injection: Store at 20ºC to 25ºC (68ºF to 77ºF); use immediately after vial is opened. Solution may discolor upon contact with metal; discard discolored solutions.
Alfuzosin: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Amifostine: Blood Pressure Lowering Agents may enhance the hypotensive effect of Amifostine. Management: When amifostine is used at chemotherapy doses, blood pressure lowering medications should be withheld for 24 hours prior to amifostine administration. If blood pressure lowering therapy cannot be withheld, amifostine should not be administered. Consider therapy modification
Amphetamines: May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy
Antipsychotic Agents (Second Generation [Atypical]): Blood Pressure Lowering Agents may enhance the hypotensive effect of Antipsychotic Agents (Second Generation [Atypical]). Monitor therapy
Barbiturates: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Benperidol: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Brigatinib: May diminish the antihypertensive effect of Antihypertensive Agents. Brigatinib may enhance the bradycardic effect of Antihypertensive Agents. Monitor therapy
Brimonidine (Topical): May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Bromperidol: Blood Pressure Lowering Agents may enhance the hypotensive effect of Bromperidol. Bromperidol may diminish the hypotensive effect of Blood Pressure Lowering Agents. Avoid combination
Dapoxetine: May enhance the orthostatic hypotensive effect of HydrALAZINE. Monitor therapy
Diazoxide: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
DULoxetine: Blood Pressure Lowering Agents may enhance the hypotensive effect of DULoxetine. Monitor therapy
Herbs (Hypertensive Properties): May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy
Herbs (Hypotensive Properties): May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Hypotension-Associated Agents: Blood Pressure Lowering Agents may enhance the hypotensive effect of Hypotension-Associated Agents. Monitor therapy
Levodopa: Blood Pressure Lowering Agents may enhance the hypotensive effect of Levodopa. Monitor therapy
Lormetazepam: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Methylphenidate: May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy
Molsidomine: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Naftopidil: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Nicergoline: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Nicorandil: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Nitroprusside: Blood Pressure Lowering Agents may enhance the hypotensive effect of Nitroprusside. Monitor therapy
Nonsteroidal Anti-Inflammatory Agents: May diminish the antihypertensive effect of HydrALAZINE. Monitor therapy
Obinutuzumab: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Management: Consider temporarily withholding blood pressure lowering medications beginning 12 hours prior to obinutuzumab infusion and continuing until 1 hour after the end of the infusion. Consider therapy modification
Pentoxifylline: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Pholcodine: Blood Pressure Lowering Agents may enhance the hypotensive effect of Pholcodine. Monitor therapy
Phosphodiesterase 5 Inhibitors: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Prostacyclin Analogues: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Quinagolide: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy
Yohimbine: May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy
Frequency not defined.
Cardiovascular: Angina pectoris, circulatory shock, flushing, orthostatic hypotension, palpitations, paradoxical pressor response, peripheral edema, tachycardia
Central nervous system: Anxiety, chills, depression, disorientation, dizziness, headache, increased intracranial pressure (IV; in patient with preexisting increased intracranial pressure), peripheral neuritis, psychotic reaction
Dermatologic: Diaphoresis, pruritus, skin rash, urticaria
Gastrointestinal: Anorexia, constipation, diarrhea, nausea, paralytic ileus, vomiting
Genitourinary: Dysuria, impotence
Hematologic & oncologic: Agranulocytosis, decreased hemoglobin, decreased red blood cells, eosinophilia, hemolytic anemia, leukopenia
Neuromuscular & skeletal: Lupus-like syndrome (dose related; fever, arthralgia, splenomegaly, lymphadenopathy, asthenia, myalgia, malaise, pleuritic chest pain, edema, positive ANA, positive LE cells, maculopapular facial rash, positive direct Coombs' test, pericarditis, pericardial tamponade), muscle cramps, rheumatoid arthritis, tremor, weakness
Ophthalmic: Conjunctivitis, lacrimation
Respiratory: Dyspnea, nasal congestion
<1%, postmarketing, and/or case reports: Hepatotoxicity (Sharma 2018), thrombocytopenia (IV)
Concerns related to adverse effects:
• Drug-induced lupus-like syndrome: May cause a drug-induced lupus-like syndrome including glomerulonephritis, especially in patients receiving higher doses. If this syndrome occurs, discontinue therapy unless the benefit-to-risk requires continued therapy. Signs and symptoms usually regress after discontinuation of therapy, but residua have been detected many years later. Long-term treatment with steroids may be necessary.
• Hematologic effects: Blood dyscrasias (eg, reduction in hemoglobin and red blood cell count, leukopenia, agranulocytosis, purpura) may occur; discontinue therapy if these hematologic effects occur.
• Hypotension: Postural hypotension may occur.
• Peripheral neuritis: Hydralazine has been associated with peripheral neuritis (eg, paresthesia, numbness, and tingling), possibly due to an antipyridoxine effect. Pyridoxine therapy should be initiated with onset of such symptoms.
• Cardiovascular disease: Use is contraindicated in patients with coronary artery disease (CAD). Use with caution in patients with cerebral vascular accidents and suspected CAD; myocardial stimulation produced by hydralazine can cause anginal attacks and electrocardiogram (ECG) changes of myocardial ischemia; has been implicated in the production of myocardial infarction. According to the American Heart Association/American College of Cardiology/American Society of Hypertension 2015 scientific statement for the treatment of hypertension in patients with CAD, hydralazine (without a concomitant nitrate [eg, isosorbide dinitrate]) should be avoided for the treatment of hypertension in patients with heart failure (with reduced ejection fraction) of ischemic origin (AHA/ACC/ASH [Rosendorff, 2015]).
• Mitral valvular disease: Use with caution in patients with mitral valvular disease; may increase pulmonary artery pressure in these patients. Use is contraindicated in patients with mitral valve rheumatic heart disease.
• Renal impairment: Use with caution in patients with advanced renal impairment; dosage adjustment recommended.
Concurrent drug therapy issues:
• Drug-drug interactions: Potentially significant interactions may exist, requiring dose or frequency adjustment, additional monitoring, and/or selection of alternative therapy. Consult drug interactions database for more detailed information.
Dosage forms related issues:
• Tartrazine sensitivity: May contain tartrazine, which may cause allergic-type reactions (including bronchial asthma) in certain susceptible individuals. Although the overall incidence of tartrazine sensitivity in the general population is low, it is frequently seen in patients who are also hypersensitive to aspirin.
Blood pressure (monitor closely with IV use), standing and sitting/supine, heart rate, complete blood cell count (CBC), antinuclear antibody (ANA) titer
The 2017 Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults (ACC/AHA [Whelton 2017]):
Confirmed hypertension and known CVD or 10-year ASCVD risk ≥10%: Target blood pressure <130/80 mm Hg is recommended.
Confirmed hypertension without markers of increased ASCVD risk: Target blood pressure <130/80 mm Hg may be reasonable.
Pregnancy Risk Factor
Adverse events have been observed in some animal reproduction studies. Hydralazine crosses the placenta (Lamont 1986; Liedholm 1982).
Intravenous hydralazine is recommended for use in the management of acute onset, severe hypertension (systolic BP ≥160 mm Hg or diastolic BP ≥110 mm Hg) with preeclampsia or eclampsia in pregnant and postpartum women (ACOG 2017).
Untreated chronic maternal hypertension is associated with adverse events in the fetus, infant, and mother. If treatment for chronic hypertension in pregnancy is needed, other oral agents are preferred as initial therapy (ACOG 2013; Magee 2014).
• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)
• Patient may experience headache, diarrhea, lack of appetite, vomiting, or nausea. Have patient report immediately to prescriber signs of lupus (rash on the cheeks or other body parts, sunburn easy, muscle or joint pain, angina or shortness of breath, or swelling in the arms or legs), change in amount of urine passed, urinary retention, severe dizziness, passing out, angina, tachycardia, abnormal heartbeat, chills, pharyngitis, burning or numbness feeling, severe loss of strength and energy, bruising, or bleeding (HCAHPS).
• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.
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Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
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- Drug class: vasodilators
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