Hydralazine (oral)

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Hydralazine (oral)
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: Turky Alkathery, M.D. [2]

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Overview

Hydralazine (oral) is a vasodilator that is FDA approved for the treatment of essential hypertension, alone or as an adjunct. 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)

Indications

  • Essential hypertension, alone or as an adjunct.

Dosage

  • Initiate therapy in gradually increasing dosages; adjust according to individual response. Start with 10 mg four times daily for the first 2 to 4 days, increase to 25 mg four times daily for the balance of the first week. For the second and subsequent weeks, increase dosage to 50 mg four times daily. For maintenance, adjust dosage to the lowest effective levels.
  • The incidence of toxic reactions, particularly the L.E. cell syndrome, is high in the group of patients receiving large doses of Hydralazine .
  • In a few resistant patients, up to 300 mg of Hydralazine daily may be required for a significant antihypertensive effect. In such cases, a lower dosage of Hydralazine combined with a thiazide and/or reserpine or a beta blocker may be considered. However, when combining therapy, individual titration is essential to ensure the lowest possible therapeutic dose of each drug.

Off-Label Use and Dosage (Adult)

Guideline-Supported Use

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

Non–Guideline-Supported Use

  • There is limited information regarding Off-Label Non–Guideline-Supported Use of Hydralazine (oral) in adult patients.

Pediatric Indications and Dosage

FDA-Labeled Indications and Dosage (Pediatric)

  • Safety and effectiveness in pediatric patients have not been established in controlled clinical trials.

Off-Label Use and Dosage (Pediatric)

Guideline-Supported Use

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

Non–Guideline-Supported Use

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

Contraindications

  • Hypersensitivity to Hydralazine ; coronary artery disease; mitral valvular rheumatic heart disease.

Warnings

  • In a few patients Hydralazine may produce a clinical picture simulating systemic lupus erythematosus including glomerulonephritis. 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

General

  • Myocardial stimulation produced by Hydralazine can cause anginal attacks and ECG changes of myocardial ischemia. The drug has been implicated in the production of myocardial infarction. It must, therefore, be used with caution in patients with suspected coronary artery disease. 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 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

  • Complete blood counts and antinuclear antibody titer determinations are indicated before and periodically during prolonged therapy with Hydralazine even though the patient is asymptomatic. *These studies are also indicated if the patient develops arthralgia, fever, chest pain, continued malaise, or other unexplained signs or symptoms.
  • A positive antinuclear antibody titer requires that the physician carefully weigh the implications of the test results against the benefits to be derived from antihypertensive therapy with Hydralazine .
  • Blood dyscrasias, consisting of reduction in hemoglobin and red cell count, leukopenia, agranulocytosis, and purpura, have been reported. If such abnormalities develop, therapy should be discontinued.

Drug/Food Interactions

  • Administration of Hydralazine with food results in higher plasma levels.

Adverse Reactions

Clinical Trials Experience

  • Adverse reactions with Hydralazine are usually reversible when dosage is reduced. However, in some cases it may be necessary to discontinue the drug. The following adverse reactions have been observed, but there has not been enough systematic collection of data to support an estimate of their frequency.
  • Common:Headache, anorexia, nausea, vomiting, diarrhea, palpitations, tachycardia, angina pectoris.
  • Less Frequent:Digestive:constipation, paralytic ileus.
  • Cardiovascular:hypotension, paradoxical pressor response, edema.
  • Respiratory:dyspnea.
  • Neurologic:peripheral neuritis, evidenced by paresthesia, numbness, and tingling; dizziness; tremors; muscle cramps; psychotic reactions characterized by depression, disorientation, or anxiety.
  • Genitourinary:difficulty in urination.
  • Hematologic:blood dyscrasias, consisting of reduction in hemoglobin and red cell count, leukopenia, agranulocytosis, purpura; lymphadenopathy; splenomegaly.
  • Hypersensitive Reactions:rash, urticaria, pruritus, fever, chills, arthralgia, eosinophilia, and rarely, hepatitis.
  • Other:nasal congestion, flushing, lacrimation, conjunctivitis.

Postmarketing Experience

  • There is limited information regarding postmarketing experience.

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 are used concomitantly.

Use in Specific Populations

Pregnancy

Pregnancy Category (FDA): C

  • Animal studies indicate that Hydralazine is teratogenic in mice at 20 to 30 times the maximum daily human dose of 200 to 300 mg and possibly in rabbits at 10 to15 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): There is no Australian Drug Evaluation Committee (ADEC) guidance on usage of Hydralazine (oral) in women who are pregnant.

Labor and Delivery

There is no FDA guidance on use of Hydralazine (oral) 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 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 in pediatric patients. The usual recommended oral starting dosage is 0.75 mg/kg of body weight daily in four divided doses. Dosage may be increased gradually over the next 3 to 4 weeks to a maximum of 7.5 mg/kg or 200 mg daily.

Geriatic Use

There is no FDA guidance on the use of Hydralazine (oral) in geriatric settings.

Gender

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

Race

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

Renal Impairment

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

Hepatic Impairment

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

Females of Reproductive Potential and Males

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

Immunocompromised Patients

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

Administration and Monitoring

Administration

  • Oral.

Monitoring

  • Renal function should be monitored and supported as required in case of overdose.

IV Compatibility

  • There is limited information regarding IV Compatibility.

Overdosage

Acute Toxicity

  • No deaths due to acute poisoning have been reported. Highest known dose survived: adults, 10 g orally. Oral LD 50 in rats: 173 and 187 mg/kg.

Signs and Symptoms

  • Signs and symptoms of overdosage include hypotension, tachycardia, headache, and generalized skin flushing.
  • Complications can include myocardial ischemia and subsequent myocardial infarction, cardiac arrhythmia, and profound shock.

Treatment

  • There is no specific antidote.
  • The gastric contents should be evacuated, taking adequate precautions against aspiration and for protection of the airway. An activated charcoal slurry may be instilled if conditions permit. These manipulations may have to be omitted or carried out after cardiovascular status has been stabilized, since they might precipitate cardiac arrhythmias or increase the depth of shock.
  • 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.

Pharmacology

Template:Px
Hydralazine (oral)
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.
  • 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.

Structure

  • Hydralazine hydrochloride, USP, is an antihypertensive, for oral administration. Its chemical name 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. Each tablet for oral administration contains 10 mg, 25 mg, 50 mg or 100 mg Hydralazine hydrochloride, USP. Tablets also contain microcrystalline cellulose, sodium starch glycolate, stearic acid, povidone K-30, colloidal silicon dioxide, mannitol and FD&C Yellow No 6.

Pharmacodynamics

  • There is limited information regarding pharmacodynamics.

Pharmacokinetics

  • Hydralazine is rapidly absorbed after oral administration, and peak plasma levels are reached at 1 to 2 hours. Plasma levels of apparent Hydralazine decline with a half-life of 3 to 7 hours. Binding to human plasma protein is 87%. Plasma levels of Hydralazine vary widely among individuals. Hydralazine is subject to polymorphic acetylation; slow acetylators generally have higher plasma levels of Hydralazine and require lower doses to maintain control of blood pressure. Hydralazine undergoes extensive hepatic metabolism; it is excreted mainly in the form of metabolites in the urine.

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.

How Supplied

  • HydrALAZINE Hydrochloride Tablets, USP:
This image is provided by the National Library of Medicine.

Storage

  • Dispense in a tight, light-resistant container.
  • Store at 20° to 25°C (68° to 77°F) [See USP Controlled Room Temperature].

Images

Drug Images

Package and Label Display Panel

This image is provided by the National Library of Medicine.
This image is provided by the National Library of Medicine.
This image is provided by the National Library of Medicine.
This image is provided by the National Library of Medicine.
This image is provided by the National Library of Medicine.

Patient Counseling Information

  • Patients should be informed of possible side effects and advised to take the medication regularly and continuously as directed.

Precautions with Alcohol

  • Alcohol-Hydralazine (oral) interaction has not been established. Talk to your doctor about the effects of taking alcohol with this medication.

Brand Names

  • HYDRALAZINE HYDROCHLORIDE®[1]

Look-Alike Drug Names

  • Apresoline - Priscoline [2]
  • hydrALAZINE - hydrOXYzine [3]

Drug Shortage Status

Price

References

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

  1. "HYDRALAZINE HYDROCHLORIDE - hydralazine hydrochloride tablet".<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  2. Institute for Safe Medication Practices: ISMP's list of confused drug names. Institute for Safe Medication Practices. Huntingdon Valley, PA. 2005. Available from URL: http://ismp.org/T... .
  3. Institute for Safe Medication Practices: ISMP's list of confused drug names. Institute for Safe Medication Practices. Huntingdon Valley, PA. 2005. Available from URL: http://ismp.org/T... .