Description: Hydralazine reduces BP and peripheral resistance but produces fluid retention. Hydralazine tends to improve renal and cerebral blood flow and its effect on diastolic pressure is more marked than on systolic pressure.
Onset: Oral: 45 min. IV: 10-20 min.
Duration: Oral and IV: 3-8 hr.
Absorption: Rapidly absorbed from the GI tract after oral admin.
Distribution: About 90% bound to plasma proteins.
Metabolism: Undergoes considerable first-pass metabolism by acetylation in the GI mucosa and liver.
Excretion: Mainly excreted in urine as metabolites.

Hydralazine is called a vasodilator. It works by relaxing blood vessels so blood can flow through the body more easily which lowers blood pressure in order to prevent strokes, heart attacks and kidney problems. It is used with or without other medications to treat high blood pressure.




Hydralazine may also be used with other medications to treat heart failure.


How to use hydralazine

Take this medication by mouth with or without food, usually 2 to 4 times daily or as directed by your doctor. The dosage is based on your medical condition and response to treatment. Your doctor may start you at a low dose and gradually increase your dose. Follow your doctor’s instructions carefully.


Use this medication regularly to get the most benefit from it. To help you remember, take it at the same times each day. It is important to continue taking this medication even if you feel well. Most people with high blood pressure do not feel sick. It may take up to several weeks before you get the full benefit of this drug.


Do not stop taking this medication without consulting your doctor. Some conditions may become worse when the drug is suddenly stopped. Your dose may need to be gradually decreased.


Tell your doctor if your condition worsens (for example, your routine blood pressure readings increase).

Headache, pounding/fast heartbeat, loss of appetite, nausea, vomiting, diarrhea, or dizziness may occur as your body adjusts to the medication. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.


To reduce the risk of dizziness, get up slowly when rising from a sitting or lying position.


This medication may infrequently cause nerve problems. Tell your doctor promptly if you experience numbness or tingling. Your doctor may recommend a vitamin B6 supplement (pyridoxine).


Tell your doctor immediately if any of these unlikely but serious side effects occur:


  • severe tiredness
  • aching/swollen joints
  • rash on nose and cheeks
  • swollen glands
  • change in the amount of urine
  • bloody/pink urine
  • signs of infection (such as fever, chills, persistent sore throat)
  • easy bruising/bleeding



Seek immediate medical attention if this rare but serious side effect occurs: chest/jaw/left arm pain.


A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any of the following symptoms of a serious allergic reaction:


  • rash
  • itching/swelling (especially of the face/tongue/throat)
  • severe dizziness
  • trouble breathing



This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

Before taking hydralazine, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies.


This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you have: a certain heart condition (coronary artery disease), a certain heart valve problem (rheumatic heart disease of the mitral valve).


Before using this medication, tell your doctor or pharmacist your medical history, especially of: blood vessel problems, previous stroke, kidney problems.


This drug may make you dizzy. Do not drive, use machinery, or do any activity that requires alertness until you are sure you can perform such activities safely. Limit alcoholic beverages.


Before having surgery, tell your doctor or dentist that you are taking this medication.


Older adults may be more sensitive to the side effects of this medication, especially dizziness, which can increase the risk of falls.


This medication should be used only when clearly needed during pregnancy. Discuss the risks and benefits with your doctor.


This medication passes into breast milk, but is unlikely to harm a nursing infant. Consult your doctor before breast-feeding.




Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use, especially of: MAO inhibitors (isocarboxazid, linezolid, methylene blue, moclobemide, phenelzine, procarbazine, rasagiline, selegiline, tranylcypromine).


Check the labels on all your medicines (such as cough-and-cold products, diet aids, or NSAIDs such as ibuprofen, naproxen) because they may contain ingredients that could increase your blood pressure/heart rate or worsen your heart failure. Ask your pharmacist about using those products safely.


This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.

If overdose is suspected, contact a poison control center or emergency room immediately. Symptoms of overdose may include:


  • severe dizziness
  • fainting
  • flushing
  • chest/jaw/left arm pain
  • irregular heartbeat.




Do not share this medication with others.


Lifestyle changes such as stress reduction programs, exercise, and dietary changes may help this medication work better.


Laboratory and/or medical tests (such as complete blood count) may be performed periodically to monitor your progress or check for side effects.


Have your blood pressure checked regularly while taking this medication.


Missed Dose

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up.



Store at room temperature between 59-86 degrees F (15-30 degrees C) away from light and moisture. Do not store in the bathroom. Keep all medicines away from children and pets.


Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company for more details about how to safely discard your product.




Available Brands

Hyperzine [ Medchem Int’l ] Phil Pharmawealth/Oboi Hydralazine [ Oboi ]


Also marketed as

Apresoline [ Novartis Healthcare ] Aprezin [ Oriental Chemical Works ]
Aprezin Tab [ Pharmasant Lab ] Endure Medical Hydralazine HCl [ Oriental Chemical Works ]

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