Hydralazine (injection)

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Hydralazine (injection)
Adult Indications & Dosage
Pediatric Indications & Dosage
Contraindications
Warnings & Precautions
Adverse Reactions
Drug Interactions
Use in Specific Populations
Administration & Monitoring
Overdosage
Pharmacology
Clinical Studies
How Supplied
Images
Patient Counseling Information
Precautions with Alcohol
Brand Names
Look-Alike Names

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Gerald Chi

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Overview

Hydralazine (injection) is a vasodilator that is FDA approved for the treatment of severe essential hypertension. Common adverse reactions include chest pain, palpitations, tachycardia, diarrhea, loss of appetite, nausea, vomiting, and headache.

Adult Indications and Dosage

FDA-Labeled Indications and Dosage (Adult)

Hypertension
  • When there is urgent need, therapy in the hospitalized patient may be initiated intramuscularly or as a rapid intravenous bolus injection directly into the vein. Hydralazine hydrochloride injection should be used only when the drug cannot be given orally.
  • Certain patients (especially those with marked renal damage) may require a lower dose. Blood pressure should be checked frequently. It may begin to fall within a few minutes after injection, with the average maximal decrease occurring in 10 to 80 minutes. In cases where there has been IICPincreased intracranial pressure, lowering the blood pressure may increase cerebral ischemia. Most patients can be transferred to oral hydralazine hydrochloride within 24 to 48 hours.
  • The product should be used immediately after the vial is opened. It should not be added to infusion solutions. Hydralazine hydrochloride injection may discolor upon contact with metal; discolored solutions should be discarded.
  • Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.
  • Dosing Information
  • 20–40 mg IV/IM, repeated as necessary.

Off-Label Use and Dosage (Adult)

Guideline-Supported Use

There is limited information regarding Off-Label Guideline-Supported Use of Hydralazine in adult patients.

Non–Guideline-Supported Use

Mitral and Aortic Incompetence
  • Dosing Information
  • 37–225 mg/day[1]
Pulmonary Hypertension
  • Dosing Information
  • 0.15–0.3 mg/kg[2]

Pediatric Indications and Dosage

FDA-Labeled Indications and Dosage (Pediatric)

Hypertension
  • Safety and effectiveness in pediatric patients have not been established in controlled clinical trials, although there is experience with the use of hydralazine hydrochloride in children.
  • Dosing Information
  • The usual recommended parenteral dosage, administered intramuscularly or intravenously, is 1.7 to 3.5 mg/kg of body weight daily, divided into four to six doses.

Off-Label Use and Dosage (Pediatric)

Guideline-Supported Use

There is limited information regarding Off-Label Guideline-Supported Use of Hydralazine in pediatric patients.

Non–Guideline-Supported Use

There is limited information regarding Off-Label Non–Guideline-Supported Use of Hydralazine in pediatric patients.

Contraindications

Warnings

  • In such patients hydralazine should be discontinued unless the benefit-to-risk determination requires continued antihypertensive therapy with this drug. Symptoms and signs usually regress when the drug is discontinued but residua have been detected many years later. Long-term treatment with steroids may be necessary.

Precautions

  • The “hyperdynamic” circulation caused by hydralazine may accentuate specific cardiovascular inadequacies. For example, hydralazine may increase pulmonary artery pressure in patients with mitral valvular disease. The drug may reduce the pressor responses to epinephrine. Postural hypotension may result from hydralazine hydrochloride but is less common than with ganglionic blocking agents. It should be used with caution in patients with cerebral vascular accidents.
  • In hypertensive patients with normal kidneys who are treated with hydralazine, there is evidence of increased renal blood flow and a maintenance of glomerular filtration rate. In some instances where control values were below normal, improved renal function has been noted after administration of hydralazine. However, as with any antihypertensive agent, hydralazine should be used with caution in patients with advanced renal damage.
  • Peripheral neuritis, evidenced by paresthesia, numbness, and tingling, has been observed. Published evidence suggests an antipyridoxine effect, and that pyridoxine should be added to the regimen if symptoms develop.
  • Laboratory Tests

Adverse Reactions

Clinical Trials Experience

There is limited information regarding Clinical Trial Experience of Hydralazine in the drug label.

Postmarketing Experience

  • Adverse reactions with hydralazine hydrochloride are usually reversible when dosage is reduced. However, in some cases it may be necessary to discontinue the drug.
  • Common adverse reactions include:
  • The following adverse reactions have been observed, but there has not been enough systematic collection of data to support an estimate of their frequency.
Neurologic
Cardiovascular

Hypotension, paradoxical pressor response, edema.

Respiratory

Dyspnea.

Gastrointestinal

Constipation, paralytic ileus.

Genitourinary

Difficulty in urination.

Hypersensitivity

Rash, urticaria, pruritus, fever, chills, arthralgia, eosinophilia, and, rarely, hepatitis.

Hematologic

Blood dyscrasias, consisting of reduction in hemoglobin and red cell count, leukopenia, agranulocytosis, purpura; lymphadenopathy; splenomegaly.

Miscellaneous

Nasal congestion, flushing, lacrimation, conjunctivitis.

Drug Interactions

  • MAO inhibitors should be used with caution in patients receiving hydralazine.
  • When other potent parenteral antihypertensive drugs, such as diazoxide, are used in combination with hydralazine, patients should be continuously observed for several hours for any excessive fall in blood pressure. Profound hypotensive episodes may occur when diazoxide injection and hydralazine injection are used concomitantly.

Use in Specific Populations

Pregnancy

Pregnancy Category (FDA):

  • Pregnancy Category C
  • Animal studies indicate that hydralazine is teratogenic in mice at 20 to 30 times the maximum daily dose of 200 to 300 mg and possibly in rabbits at 10 to 15 times the maximum daily human dose, but that it is nonteratogenic in rats. Teratogenic effects observed were cleft palate and malformations of facial and cranial bones.
  • There are no adequate and well-controlled studies in pregnant women. Although clinical experience does not include any positive evidence of adverse effects on the human fetus, hydralazine should be used during pregnancy only if the expected benefit justifies the potential risk to the fetus.


Pregnancy Category (AUS):

  • Australian Drug Evaluation Committee (ADEC) Pregnancy Category C

There is no Australian Drug Evaluation Committee (ADEC) guidance on usage of Hydralazine in women who are pregnant.

Labor and Delivery

There is no FDA guidance on use of Hydralazine during labor and delivery.

Nursing Mothers

  • It is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when hydralazine injection is administered to a nursing woman.

Pediatric Use

  • Safety and effectiveness in pediatric patients have not been established in controlled clinical trials, although there is experience with the use of hydralazine hydrochloride in children. The usual recommended parenteral dosage, administered intramuscularly or intravenously, is 1.7 to 3.5 mg/kg of body weight daily, divided into four to six doses.

Geriatic Use

There is no FDA guidance on the use of Hydralazine with respect to geriatric patients.

Gender

There is no FDA guidance on the use of Hydralazine with respect to specific gender populations.

Race

There is no FDA guidance on the use of Hydralazine with respect to specific racial populations.

Renal Impairment

There is no FDA guidance on the use of Hydralazine in patients with renal impairment.

Hepatic Impairment

There is no FDA guidance on the use of Hydralazine in patients with hepatic impairment.

Females of Reproductive Potential and Males

There is no FDA guidance on the use of Hydralazine in women of reproductive potentials and males.

Immunocompromised Patients

There is no FDA guidance one the use of Hydralazine in patients who are immunocompromised.

Administration and Monitoring

Administration

  • Oral
  • Intravenous

Monitoring

There is limited information regarding Monitoring of Hydralazine in the drug label.

IV Compatibility

There is limited information regarding IV Compatibility of Hydralazine in the drug label.

Overdosage

Acute Overdose

Signs and Symptoms

  • No deaths due to acute poisoning have been reported.
  • Highest known dose survived: adults, 10 g orally. Oral LD50 in rats: 173 and 187 mg/kg.

Management

  • There is no specific antidote.
  • Support of the cardiovascular system is of primary importance. Shock should be treated with plasma expanders. If possible, vasopressors should not be given, but if a vasopressor is required, care should be taken not to precipitate or aggravate cardiac arrhythmia. Tachycardia responds to beta blockers. Digitalization may be necessary, and renal function should be monitored and supported as required.
  • No experience has been reported with extracorporeal or peritoneal dialysis.

Chronic Overdose

There is limited information regarding Chronic Overdose of Hydralazine in the drug label.

Pharmacology

Template:Px
Hydralazine (injection)
Systematic (IUPAC) name
1-hydrazinylphthalazine
Identifiers
CAS number 86-54-4
ATC code C02DB02
PubChem 3637
DrugBank DB01275
Chemical data
Formula Template:OrganicBox atomTemplate:OrganicBox atomTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBox atomTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBox 
Mol. mass 160.176 g/mol
SMILES eMolecules & PubChem
Pharmacokinetic data
Bioavailability 26-50%
Protein binding 85-90%
Metabolism Hepatic
Half life 2-8 hours, 7-16 hours (renal impairment)
Excretion Renal
Therapeutic considerations
Licence data

US

Pregnancy cat.

C(AU) C(US)

Legal status

Prescription Only (S4)(AU) ?(CA) POM(UK) [[Prescription drug|Template:Unicode-only]](US)

Routes Oral, intravenous

Mechanism of Action

  • Although the precise mechanism of action of hydralazine is not fully understood, the major effects are on the cardiovascular system. Hydralazine apparently lowers blood pressure by exerting a peripheral vasodilating effect through a direct relaxation of vascular smooth muscle. Hydralazine, by altering cellular calcium metabolism, interferes with the calcium movements within the vascular smooth muscle that are responsible for initiating or maintaining the contractile state.

Structure

  • Hydralazine Hydrochloride Injection, USP is an antihypertensive available in a 1 mL vial for intravenous and intramuscular administration. Hydralazine Hydrochloride Injection USP is a sterile, nonpyrogenic colorless solution.
  • Hydralazine Hydrochloride USP is 1-hydrazinophthalazine monohydrochloride, and its structural formula is:
This image is provided by the National Library of Medicine.
  • Hydralazine Hydrochloride USP is a white to off-white, odorless crystalline powder. It is soluble in water, slightly soluble in alcohol, and very slightly soluble in ether. It melts at about 275°C, with decomposition, and has a molecular weight of 196.64.

Pharmacodynamics

  • The peripheral vasodilating effect of hydralazine results in decreased arterial blood pressure (diastolic more than systolic), decreased peripheral vascular resistance, and an increased heart rate, stroke volume, and cardiac output. The preferential dilatation of arterioles, as compared to veins, minimizes postural hypotension and promotes the increase in cardiac output. Hydralazine usually increases renin activity in plasma, presumably as a result of increased secretion of renin by the renal juxtaglomerular cells in response to reflex sympathetic discharge. This increase in renin activity leads to the production of angiotensin II, which then causes stimulation of aldosterone and consequent sodium reabsorption. Hydralazine also maintains or increases renal and cerebral blood flow.

Pharmacokinetics

  • The average maximal decrease in blood pressure usually occurs 10 to 80 minutes after administration of Hydralazine Hydrochloride Injection. No other pharmacokinetic data on Hydralazine Hydrochloride Injection are available.

Nonclinical Toxicology

Carcinogenesis, Mutagenesis, Impairment of Fertility
  • In a lifetime study in Swiss albino mice, there was a statistically significant increase in the incidence of lung tumors (adenomas and adenocarcinomas) of both male and female mice given hydralazine continuously in their drinking water at a dosage of about 250 mg/kg per day (about 80 times the maximum recommended human dose). In a 2-year carcinogenicity study of rats given hydralazine by gavage at dose levels of 15, 30, and 60 mg/kg/day (approximately 5 to 20 times the recommended human daily dosage), microscopic examination of the liver revealed a small, but statistically significant, increase in benign neoplastic nodules in male and female rats from the high-dose group and in female rats from the intermediate-dose group. Benign interstitial cell tumors of the testes were also significantly increased in male rats from the high-dose group. The tumors observed are common in aged rats and a significantly increased incidence was not observed until 18 months of treatment. Hydralazine was shown to be mutagenic in bacterial systems (Gene Mutation and DNA Repair) and in one of two rats and one rabbit hepatocyte in vitro DNA repair studies.
  • Additional in vivo and in vitro studies using lymphoma cells, germinal cells, and fibroblasts from mice, bone marrow cells from Chinese hamsters and fibroblasts from human cell lines did not demonstrate any mutagenic potential for hydralazine.
  • The extent to which these findings indicate a risk to man is uncertain. While long-term clinical observation has not suggested that human cancer is associated with hydralazine use, epidemiologic studies have so far been insufficient to arrive at any conclusions.

Clinical Studies

There is limited information regarding Clinical Studies of Hydralazine in the drug label.

How Supplied

  • Hydralazine Hydrochloride Injection USP, 20 mg/mL
NDC 17478-834-01 1 mL Single-dose Vial Packaged in boxes of 10
NDC 17478-834-15 1 mL Single-dose Vial Packaged in boxes of 25
  • Storage: Store at 20° to 25°C (68° to 77°F).

Storage

There is limited information regarding Hydralazine (injection) Storage in the drug label.

Images

Drug Images

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This pill image is provided by the National Library of Medicine's PillBox.

Package and Label Display Panel

Hydralazine02.jpeg
This image of the FDA label is provided by the National Library of Medicine.
Hydralazine03.jpeg
This image of the FDA label is provided by the National Library of Medicine.
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This image of the FDA label is provided by the National Library of Medicine.

Patient Counseling Information

There is limited information regarding Patient Counseling Information of Hydralazine in the drug label.

Precautions with Alcohol

  • Alcohol-Hydralazine interaction has not been established. Talk to your doctor about the effects of taking alcohol with this medication.[3]

Brand Names

  • Apresoline®

Look-Alike Drug Names

  • Apresoline® — Priscoline®[4]
  • hydrALAZINE — hydrOXYzine[4]

Drug Shortage Status

Price

References

The contents of this FDA label are provided by the National Library of Medicine.

  1. Jensen, T. (1983-05). "Treatment with hydralazine in mild to moderate mitral or aortic incompetence". European Heart Journal. 4 (5): 306–312. ISSN 0195-668X. PMID 6617676. Unknown parameter |coauthors= ignored (help); Check date values in: |date= (help)<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  2. McGoon, M. D. (1983-12). "Haemodynamic response to intravenous hydralazine in patients with pulmonary hypertension". British Heart Journal. 50 (6): 579–585. ISSN 0007-0769. PMC 481463. PMID 6652000. Unknown parameter |coauthors= ignored (help); Check date values in: |date= (help)<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  3. "HYDRALAZINE HYDROCHLORIDE injection".<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
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