Hydralazine

Mechanism-of-action class: Unknown Cellular or Molecular Interaction.

• Essential hypertension, alone or as an adjunct.ICD-10: I10

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

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 hydrochloride tablets. In a few resistant patients, up to 300 mg of hydrALAZINE hydrochloride tablets daily may be required for a significant antihypertensive effect. In such cases, a lower dosage of hydrALAZINE hydrochloride tablets 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.

​ 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. (See PRECAUTIONS, Laboratory Tests .)

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.

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.

• Oct 23, 1978ANDAANDA086242Heritage
• May 1, 1984ANDAANDA088467Pliva
• May 1, 1984ANDAANDA088468Pliva
• Dec 18, 1985ANDAANDA089097Pliva
• Dec 18, 1985ANDAANDA089098Pliva
• Jun 30, 1997ANDAANDA040136Am Regent
• Mar 13, 2001ANDAANDA040388Fresenius Kabi Usa
• Jun 23, 2005NDANDA020727Azurity

1. 1Chronic Kidney Disease2,8549.7%
2. 2Acute Kidney Injury2,6719.1%
3. 3Renal Failure2,1347.2%
4. 4End Stage Renal Disease1,6055.4%
5. 5Dyspnoea1,6035.4%
6. 6Fatigue1,5995.4%
7. 7Diarrhoea1,4655.0%
8. 8Nausea1,4114.8%
9. 9Drug Ineffective1,3774.7%
10. 10Death1,3624.6%
11. 11Hypertension1,3624.6%
12. 12Off Label Use1,2364.2%
13. 13Anti-neutrophil Cytoplasmic Antibody Positive Vasculitis1,0633.6%
14. 14Asthenia1,0123.4%
15. 15Dizziness1,0093.4%

Recent PubMed references pinned to Hydralazine as a MeSH major topic. Citations link to pubmed.ncbi.nlm.nih.gov.

• Impact of N-Acetylation on DNA Damage and Oxidative Stress Responses in Mammalian Cells and Human Hepatocytes Treated with Hydralazine.
  Biomolecules · 2026 · Habil MR, Stephens MA, Cass AA, et al.
  PMID 42072683DOI 10.3390/biom16040562
• Glutathione-reversible inactivation of aldehyde oxidase by hydralazine contributes to inter-lot inhibition variability in human hepatocytes.
  Drug metabolism and pharmacokinetics · 2026 · Tang LWT
  PMID 41955649DOI 10.1016/j.dmpk.2026.101537
• Hydralazine Use and Risk of Vasculitis.
  JAMA network open · 2026 · Fremont D, Dhaliwal S, Canney M, et al.
  PMID 41838000DOI 10.1001/jamanetworkopen.2026.1943
• Cryptococcid Sweet Syndrome in the Setting of Hydralazine-Induced ANCA Vasculitis: A Case Report.
  Journal of cutaneous pathology · 2026 · Vroman J, Sagut P, Lynam K, et al.
  PMID 41437934DOI 10.1111/cup.70044
• Anxiolytic effects of crystal and polycrystal of hydrazone derived from hydralazine in adult zebrafish.
  Biochemical and biophysical research communications · 2026 · Cavalcante MMB, Teixeira CR, Ferreira MKA, et al.
  PMID 41401543DOI 10.1016/j.bbrc.2025.153106
• Association of hydralazine use with risk of hematologic neoplasms in patients with hypertension: A nationwide population-based cohort study in Taiwan.
  PLoS medicine · 2025 · Wang LT, Chien WC, Ma KS, et al.
  PMID 41343491DOI 10.1371/journal.pmed.1004646
• Expanding Metabolome Coverage in LC-MS/MS Analysis through Hydralazine-Based Multifunctional Derivatization.
  Analytical chemistry · 2025 · Yan Z, Tang W, Li B, et al.
  PMID 41277254DOI 10.1021/acs.analchem.5c02101
• Drug reactions with aldehyde adducts as a novel route to protein haptenisation: Recent tentative clinical evidence for a role in hydralazine vasotoxicity.
  Biochemical pharmacology · 2026 · Burcham PC
  PMID 41161543DOI 10.1016/j.bcp.2025.117467

The 10 most recently updated of 75 ClinicalTrials.gov registrations naming Hydralazine as an intervention. Registration is not evidence of efficacy or safety — reference crosswalk only.

• DANHEART (H-HeFT and Met-HeFT)
  Completed · Phase 4 · Interventional · 1,100 enrolled · Henrik Wiggers
  NCT03514108updated 2026-06-11
• Efficacy and Safety of Qishen Yiqi Dropping Pills in Patients With Severe Pulmonary Hypertension
  Recruiting · Interventional · 120 enrolled · Guangdong Provincial People's Hospital
  NCT07604805updated 2026-05-22
• Comparison of Intravenous Labetalol and Intravenous Hydralazine in Severe Preeclampsia
  Completed · Interventional · 132 enrolled · Muhammad Aamir Latif
  NCT07572656updated 2026-05-07
• Comparison of Post-Craniotomy Blood Pressure Targets
  Enrolling by invitation · Interventional · 500 enrolled · Vanderbilt University Medical Center
  NCT07093151updated 2026-04-21
• Pharmacokinetics, Pharmacodynamics, and Safety Profile of Understudied Drugs Administered to Children Per Standard of Care (POPS)
  Recruiting · Observational · 5,000 enrolled · Duke University
  NCT04278404updated 2026-04-06
• Baroreflex Activation Therapy for Heart Failure
  Completed · Interventional · 1,090 enrolled · CVRx, Inc.
  NCT02627196updated 2026-03-10
• Inhaled Treprostinil in Sarcoidosis Patients With Pulmonary Hypertension
  Completed · Phase 2 · Interventional · 5 enrolled · University of Florida
  NCT03814317updated 2026-02-06
• Verification of the Efficacy and Safety of the BAROSTIM NEO System in the Treatment of Drug Resistant Hypertension
  Active not recruiting · Interventional · 40 enrolled · CVRx, Inc.
  NCT01471834updated 2025-07-15
• Evaluation of TRANSKRIP ® Plus Chemotherapy in Recurrent-Persistent Cervical Cancer
  Withdrawn · Phase 3 · Interventional · 0 enrolled · National Institute of Cancerología
  NCT02446652updated 2025-05-29
• Intravenous Labetalol Versus Hydralazine in Preeclampsia
  Unknown · Phase 1 · Phase 2 · Interventional · 40 enrolled · Tanta University
  NCT06360601updated 2024-12-02

CPIC-curated drug–gene pairs for Hydralazine. Levels describe the strength of curated evidence and guideline status — never a recommendation to test or to adjust therapy.

• NAT2CPIC AClinPGx 1AFDA label: Actionable PGx
  NAT2 and Hydralazine

Frequently asked questions

How does Hydralazine work?

Mechanism-of-action class: Unknown Cellular or Molecular Interaction.

What is Hydralazine used for?

According to FDA labeling, Hydralazine carries indications including: Essential hypertension, alone or as an adjunct.. This is a reference summary of labeled uses, not medical advice or a treatment recommendation.

What class of drug is Hydralazine?

Hydralazine is classified as Hydrazinophthalazine derivatives, Arteriolar Vasodilator, Unknown Cellular or Molecular Interaction, Arterial Vasodilation, Arteriolar Vasodilation, Decreased Blood Pressure, Decreased Vascular Smooth Muscle Tone.

What are the brand names for Hydralazine?

Hydralazine is marketed under brand names including Bidil.

What are the contraindications for Hydralazine?

Hydralazine labeling lists contraindications including: Hypersensitivity to hydrALAZINE; coronary artery disease; mitral valvular rheumatic heart disease.. Always consult the full prescribing information and a clinician.