III. Contraindications

  1. Ischemic Heart Disease (Hydralazine provokes Angina)

IV. Mechanism

  1. Arteriole dilation (independent of sympathetic drive)
  2. Decreases Blood Pressure with compensatory reflex Tachycardia
  3. Increases Cardiac Output and renal Blood Flow

V. Dosing: Hydralazine (Adults)

  1. Hypertensive Emergency
    1. Hydralazine: 10-20 mg IV (or 10 to 50 mg IM) every 4 to 6 hours as needed
  2. Pregnancy Induced Hypertension (Preeclampsia)
    1. Start: 5 mg IV (or 10 mg IM) every 20 minutes prn
    2. Maintenance: 5 to 10 mg IV (or 10 mg to 20 mg IM) every 3 hours prn
  3. Hypertension
    1. Start 10 mg orally taken 2 to 4 times daily for 3-4 days
    2. Next 25 mg orally take 2 to 4 times daily
    3. Titrate as needed to 50 mg orally 2 to 4 times daily
    4. Maximum: 300 mg/day
    5. Renal Adjustment
      1. GFR 10 to 50 ml/min: Decrease dosing frequency to every 8 hours
      2. GFR <10 ml/min: Decrease dosing frequency to every 8 to 16 hours (up to every 24 hours)
  4. Congestive Heart Failure
    1. Start 10 to 25 mg orally three times daily
    2. Target 75 mg orally three times daily
    3. Maximum 100 mg orally three times daily
    4. Often combined with Isosorbide (see BiDil below)

VI. Dosing: Hydralazine (Children, not FDA approved)

  1. Hypertensive Urgency or Emergency
    1. Start 0.1 to 0.2 mg/kg (up to 20 mg) IV or IM every 4 to 6 hours as needed
  2. Hypertension
    1. Start 0.75 to 1 mg/kg/day orally divided 2 to 4 times daily
    2. May titrate over the next month up to 7.5 mg mg/kg/day divided 2 to 4 times daily (up to 25 mg/dose)

VII. Dosing: Hydralazine Combinations

  1. Hydralazine with Isosorbide Dinitrate 37.5/20 (BiDil)
    1. Dose: 1-2 tablets orally three times daily
    2. Indicated Class III CHF patients (esp. African American)
    3. Very expensive: $400/month (Generic Drugs separately are $60/month)

VIII. Adverse Effects

  1. Headache
  2. Palpitations
  3. Reflex Tachycardia
    1. Includes Fetal Tachycardia (in Preeclampsia)
    2. Beta Blockers are often used in combination with Beta Blockers to counter reflex Tachycardia
  4. Leg Edema
    1. Due to reflex Sodium and water retention
    2. Diuretics are often combined with Hydralazine
  5. Dizziness
  6. Nausea
  7. Nasal Congestion
  8. Hepatitis
  9. Angina (in pre-existing Ischemic Heart Disease)
  10. Systemic Lupus Erythematosus Like Syndrome
  11. Peripheral Neuritis
    1. Hydralazine interferes with Vitamin B6 metabolism in neural tissue

IX. Safety

  1. Pregnancy Category C
  2. Considered safe in Lactation

X. Metabolism

  1. Excreted unchanged as well as with acetylated metabolites
  2. Lower serum levels in rapid acetylators

XII. References

  1. (2020) Med Lett Drugs Ther 62(1598): 73-80
  2. Olson (2020) Clinical Pharmacology, Medmaster Miami, p. 66-7
  3. Hamilton (2020) Tarascon Pocket Pharmacopoeia

Images: Related links to external sites (from Bing)

Related Studies

Cost: Medications

hydralazine (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing)
HYDRALAZINE 10 MG TABLET Generic $0.03 each
HYDRALAZINE 100 MG TABLET Generic $0.08 each
HYDRALAZINE 25 MG TABLET Generic $0.04 each
HYDRALAZINE 50 MG TABLET Generic $0.05 each
bidil (on 10/1/2022 at Medicaid.Gov Survey of pharmacy drug pricing)
BIDIL 20 MG-37.5 MG TABLET Generic $1.58 each

Ontology: Hydralazine (C0020223)

Definition (NCI) A phthalazine derivative with antihypertensive effects. Hydralazine exerts its vasodilatory effects through modification of the contractile state of arterial vascular smooth muscle by altering intracellular calcium release, and interfering with smooth muscle cell calcium influx. This agent also causes inhibition of phosphorylation of myosin protein or chelation of trace metals required for smooth muscle contraction, thereby resulting in an increase in heart rate, stroke volume and cardiac output.
Definition (MSH) A direct-acting vasodilator that is used as an antihypertensive agent.
Definition (CSP) direct-acting vasodilator that is used as an antihypertensive.
Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH D006830
SnomedCT 22696000, 387125005
LNC LP15169-3, MTHU002558
English Apressin, Hydralazine, Hydrallazin, Hydrazinophthalazine, 1(2H)-Phthalazinone, hydrazone, apressin, 1(2H)-Phthalazinone Hydrazone, Hydralazine [Chemical/Ingredient], HYDRALAZINE, hydrALAZINE, hydralazine (medication), hydralazine, Apressinum, Hydralazine (product), Hydralazine (substance)
Swedish Hydralazin
Czech hydralazin
Finnish Hydralatsiini
Russian APRESSIN, GIDRALAZIN, АПРЕССИН, ГИДРАЛАЗИН
Italian Apressina, Idrallazina, Idrazinoftalazina, Idralazina
Spanish Hidralazina, Hidralacina, hidralazina (producto), hidralazina (sustancia), hidralazina
Polish Hydralazyna
Japanese ヒドララジン, 塩酸ヒドララジン
French Hydralazine
German Hydralazin, Hydrallazin
Portuguese Hidralazina

Ontology: Apresoline (C0699178)

Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH D006830
English Apresoline, apresoline, Apressoline

Ontology: Bidil (C0968130)

Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH C431665
English Bidil, BiDil