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Skeletal formula of hydralazine
Ball-and-stick model of the hydralazine molecule
Clinical data
Trade namesApresoline, BiDil, others
License data
  • AU: C
  • US: C (Risk not ruled out)
Routes of
By mouth, intravenous
ATC code
Legal status
Legal status
Pharmacokinetic data
Protein binding85–90%
Onset of action5 to 30 min[1]
Elimination half-life2–8 hours, 7–16 hours (renal impairment)
Duration of action2 to 6 hrs[1]
CAS Number
PubChem CID
CompTox Dashboard (EPA)
ECHA InfoCard100.001.528 Edit this at Wikidata
Chemical and physical data
Molar mass160.176 g/mol g·mol−1
3D model (JSmol)

Hydralazine, sold under the brand name Apresoline among others, is a medication used to treat high blood pressure and heart failure.[1] This includes high blood pressure in pregnancy and very high blood pressure resulting in symptoms.[2] It has been found to be particularly useful in heart failure together with isosorbide dinitrate in people of African descent.[1] It is given by mouth or by injection into a vein.[2] Effects usually begin around 15 minutes and last up to six hours.[1]

Common side effects include headache and fast heart rate.[1] It is not recommended in people with coronary artery disease or in those with rheumatic heart disease that affects the mitral valve.[1] In those with kidney disease a low dose is recommended.[2] Hydralazine is in the vasodilator family of medications and is believed to work by causing the dilation of blood vessels.[1]

Hydralazine was discovered while scientists at Ciba were looking for a treatment for malaria.[3] It was patented in 1949.[4] It is on the World Health Organization's List of Essential Medicines, the safest and most effective medicines needed in a health system.[5] The wholesale cost in the developing world is about US$2.78–9.11 per month.[6] In the United States treatment costs about $50–100 per month.[7] In 2016 it was the 138th most prescribed medication in the United States with more than 4 million prescriptions.[8]

Medical use[edit]

Hydralazine is not used as a primary drug for treating hypertension because it elicits a reflex sympathetic stimulation of the heart (the baroreceptor reflex).[9] The sympathetic stimulation may increase heart rate and cardiac output, and in people with coronary artery disease may cause angina pectoris or myocardial infarction.[10] Hydralazine may also increase plasma renin concentration, resulting in fluid retention. To prevent these undesirable side effects, hydralazine is usually prescribed in combination with a β-blocker (e.g., propranolol) and a diuretic.[10] Beta-blockers licensed to treat heart failure in the UK include bisoprolol, carvedilol, and nebivolol.[citation needed]

Hydralazine is used to treat severe hypertension, but again, it is not a first-line therapy for essential hypertension. However, hydralazine is often used to treat hypertension in pregnancy, with methyldopa.[11]

Hydralazine is commonly used in combination with isosorbide dinitrate for the treatment of congestive heart failure in self-identified African American populations. This preparation, isosorbide dinitrate/hydralazine, was the first race-based prescription drug.[12]

It should not be used in people with tachycardia, heart failure, who have constrictive pericarditis, who have lupus, a dissecting aortic aneurysm, or porphyria.[13]

Adverse effects[edit]

Prolonged treatment may cause a syndrome similar to lupus which can become fatal if the symptoms are not noticed and drug treatment stopped.[13]

Very common (>10% frequency) side effects include headache, high heart rate, and palpitations.[13]

Common (1–10% frequency) side effects include flushing, hypotension, anginal symptoms, aching or swelling joints, muscle aches, positive tests for ANP, stomach upset, diarrhea, nausea, and vomiting, and swelling (sodium and water retention).[13]


It may potentiate the antihypertensive effects of:[13]

Drugs subject to a strong first-pass effect such as β-blockers may increase the bioavailability of hydralazine.[13] Epinephrine (adrenaline)'s heart rate-accelerating effects are increased by hydralazine, hence may lead to toxicity.[13]

Mechanism of action[edit]

It is a direct-acting smooth muscle relaxant and acts as a vasodilator primarily in resistance arterioles; the molecular mechanism was unknown as of 2011.[9][14] By relaxing vascular smooth muscle, vasodilators act to decrease peripheral resistance, thereby lowering blood pressure and decreasing afterload.[10]


Hydralazine belongs to the hydrazinophthalazine class of drugs.[15]


The antihypertensive activity of hydralazine was discovered by scientists at Ciba who were trying to discover drugs to treat malaria; it was initially called C-5968 and 1-hydrazinophthalazine; Ciba's patent application was filed in 1945 and issued in 1949,[16][17][18] and the first scientific publications of its blood-pressure lowering activities appeared in 1950.[3][15][19] It was approved by the FDA in 1953.[20]

It was one of the first antihypertensive medications that could be taken by mouth.[9]


Hydralazine has also been studied as a treatment for myelodysplastic syndrome in its capacity as a DNA methyltransferase inhibitor.[21]

See also[edit]


  1. ^ a b c d e f g h "Hydralazine Hydrochloride". The American Society of Health-System Pharmacists. Archived from the original on 21 December 2016. Retrieved 8 December 2016.
  2. ^ a b c World Health Organization (2009). Stuart MC, Kouimtzi M, Hill SR (eds.). WHO Model Formulary 2008. World Health Organization. p. 280. hdl:10665/44053. ISBN 9789241547659.
  3. ^ a b Wermuth CG (2011-05-02). The Practice of Medicinal Chemistry. Academic Press. p. 12. ISBN 9780080568775. Archived from the original on 2017-02-26.
  4. ^ Progress in Drug Research/Fortschritte der Arzneimittelforschung/Progrés des recherches pharmaceutiques. Birkhäuser. 2013. p. 206. ISBN 9783034870948. Archived from the original on 2016-12-20.
  5. ^ World Health Organization (2019). World Health Organization model list of essential medicines: 21st list 2019. Geneva: World Health Organization. hdl:10665/325771. WHO/MVP/EMP/IAU/2019.06. License: CC BY-NC-SA 3.0 IGO.
  6. ^ "Hydralazine". International Drug Price Indicator Guide. Retrieved 8 December 2016.
  7. ^ Hamilton R (2015). Tarascon Pocket Pharmacopoeia 2015 Deluxe Lab-Coat Edition. Jones & Bartlett Learning. p. 145. ISBN 9781284057560.
  8. ^ "The Top 300 of 2019". clincalc.com. Retrieved 22 December 2018.
  9. ^ a b c Kandler MR, Mah GT, Tejani AM, Stabler SN, Salzwedel DM (November 2011). "Hydralazine for essential hypertension". The Cochrane Database of Systematic Reviews (11): CD004934. doi:10.1002/14651858.CD004934.pub4. PMID 22071816.
  10. ^ a b c Harvey RA, Harvey PA, Mycek MJ (2000). Lippincott's Illustrated Reviews: Pharmacology (2nd ed.). Philadelphia: Lippincott Williams & Wilkins. p. 190.
  11. ^ Bhushan V, Lee TT, Ozturk A (2007). First Aid for the USMLE Step 1. New York: McGraw-Hill Medical. p. 251.
  12. ^ Ferdinand KC, Elkayam U, Mancini D, Ofili E, Piña I, Anand I, et al. (July 2014). "Use of isosorbide dinitrate and hydralazine in African-Americans with heart failure 9 years after the African-American Heart Failure Trial". The American Journal of Cardiology. 114 (1): 151–9. doi:10.1016/j.amjcard.2014.04.018. PMID 24846808.
  13. ^ a b c d e f g "Hydralazine Tablets 50mg". UK Electronic Medicines Compendium. September 7, 2016. Archived from the original on February 27, 2017.
  14. ^ Cohn JN, McInnes GT, Shepherd AM (September 2011). "Direct-acting vasodilators". Journal of Clinical Hypertension. 13 (9): 690–2. doi:10.1111/j.1751-7176.2011.00507.x. PMID 21896152.
  15. ^ a b Schroeder NA (January 1952). "The effect of 1-hydrasinophthalasine in hypertension". Circulation. 5 (1): 28–37. doi:10.1161/01.cir.5.1.28. PMID 14896450.
  16. ^ "Hydralazine". Drugbank. Archived from the original on 4 March 2017. Retrieved 4 March 2017.
  17. ^ "hydralazine". PubChem. Archived from the original on 4 March 2017. Retrieved 4 March 2017.
  18. ^ US2484029; see Example 1
  19. ^ Reubi FC (January 1950). "Renal hyperemia induced in man by a new phthalazine derivative". Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine. 73 (1): 102–103. doi:10.3181/00379727-73-17591. PMID 15402536.
  20. ^ "New Drug Application (NDA) 008303 Company: NOVARTIS Drug Name(s): Apresoline". FDA. Archived from the original on 26 February 2017. Retrieved 26 February 2017.
  21. ^ Singh V, Sharma P, Capalash N (May 2013). "DNA methyltransferase-1 inhibitors as epigenetic therapy for cancer". Current Cancer Drug Targets. 13 (4): 379–99. doi:10.2174/15680096113139990077. PMID 23517596.