Hydralazine is a generic prescription blood pressure drug, but it’s usually not a first choice for treatment. Healthcare providers more commonly use it when other drugs are not effective enough, or in certain emergency situations. Available as a tablet or injection, hydralazine doses typically need to be taken or administered three to four times a day.
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Hydralazine overview
BRAND NAMES:
No brand-name versions
Generic Names:
Hydralazine HCl
Uses:
Treats high blood pressure and hypertensive emergencies
Therapeutic Classes:
Antihypertensive, peripheral vasodilator
Forms:
Tablet, injection
How it’s taken:
By mouth, injection
What is Hydralazine used for?
Healthcare professionals use hydralazine to manage patients with high blood pressure, especially when other drugs are not effective enough. They also use it to treat blood pressure emergencies, including hypertensive crisis, eclampsia, or preeclampsia. Hydralazine is commonly used off-label to treat heart failure, often in combination with the medicine isosorbide dinitrate.
Key takeaways
Take hydralazine exactly as directed by your healthcare provider, and keep all appointments for follow-up and labs.
Since hydralazine is typically taken 3 or 4 times daily, you can use a smartphone or alarm to remember to take your doses.
You can take hydralazine with or without food, but it is best to take it the same way each time—always with food, or always without food.
If you have any questions or concerns, consult your healthcare provider for medical advice.
What form(s) does Hydralazine come in
Tablets
10 mg
25 mg
50 mg
100 mg
Injection
20 mg/mL
What are common Hydralazine doses?
Doses may vary, and these are general guidelines. Always follow the dosing directions given by your healthcare provider.
For high blood pressure (oral): Starting dose is 10 mg by mouth four times daily for two to four days, then 25 mg four times daily for the balance of the first week, then may increase to 50 mg four times daily if more blood pressure control is needed. The usual dose ranges from 100 to 200 mg per day in two to four doses.
For high blood pressure (injection): 10–20 mg intravenous or 10–50 mg intramuscular injection every four to six hours as needed; healthcare provider will switch to oral form as soon as possible
For heart failure (off-label): 25–50 mg taken three or four times daily; healthcare provider will increase as required. For heart failure, hydralazine is typically taken along with other medications.
Common Hydralazine prescriptions
hydrALAZINE HCl
100mg tablethydrALAZINE HCl
10mg tablethydrALAZINE HCl
25mg tablethydrALAZINE HCl
50mg tablethydrALAZINE HCl
1ml of 20mg/ml vial
How to take Hydralazine
Take this medication as prescribed. The dose may need to be changed several times to find what works best for you.
Doses are taken three to four times per day. Use an alarm or smartphone to help you remember to take doses.
Take doses at the same time every day.
Hydralazine may be taken with or without food, but must be taken that way every time.
Hydralazine injections are administered by a healthcare professional.
Store hydralazine tablets at room temperature out of the reach of children.
What to do if you miss a dose of Hydralazine
If you miss a dose, take it as soon as you remember.
If it is almost time for the next dose, skip the missed dose and take your next dose at the regular time.
Do not take two doses to make up for a missed dose.
Hydralazine contraindications
This medicine is not right for everyone. Before taking hydralazine, tell your healthcare provider about your medical history and medical conditions.
Do not use it if you have had an allergic reaction to hydralazine or if you have:
Coronary artery disease (CAD)
Rheumatic heart disease
Hydralazine warnings
Tell any doctor or other healthcare provider who treats you that you are using this medicine.
The prescriber may recommend regular visits and lab tests to monitor the effectiveness and side effects of this treatment. Keep all appointments.
Tell the prescriber if you are pregnant, breastfeeding, or have:
Kidney disease
Heart disease
Chest pain (angina)
Heart rhythm irregularities
Blood vessel disease
Low blood pressure
Lupus
Peripheral neuritis (tingling and numbness)
A history of heart attack or stroke
Hydralazine can cause serious problems, including:
Heart rhythm abnormalities
Chest pain
Nerve problems including numbness and tingling
Lupus-like symptoms
This medicine may lower your blood pressure too much and cause dizziness, lightheadedness, or fainting. Do not drive or do anything else that could be dangerous until you know how this medicine affects you.
Check with your healthcare provider about alcohol use while taking hydralazine, as alcohol can worsen some of the side effects of this medicine.
Hydralazine interactions
To avoid drug interactions, tell the prescribing healthcare provider about all prescription drugs, over-the-counter medicines, vitamins, and supplements being taken before starting hydralazine, particularly:
Other drugs that lower blood pressure
Monoamine oxidase inhibitors (MAOIs)
Hydralazine side effects
Serious side effects
Get emergency medical help right away if you notice any signs or symptoms of a possible serious side effect, including:
Fast, pounding, or uneven heartbeat
Chest pain (which may spread to your arms, jaw, back, or neck), trouble breathing, unusual sweating, faintness
Blistering, peeling, red skin rash
Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
Call your healthcare provider right away if you have any of the following symptoms:
Fatigue, fever, muscle pain, joint pain
Change in how much or how often you urinate
Numbness, tingling, or burning pain in your hands, arms, legs, or feet
Common side effects
Nausea, vomiting, diarrhea
Loss of appetite
Headache
Consult your pharmacist or other healthcare provider for more information about adverse effects of hydralazine.
Sources:
2020 clinical management guidelines for obstetrician-gynecologists: Gestational hypertension and preeclampsia, The American College of Obstetricians and Gynecologists (ACOG) (2020)
Apresoline drug summary, Prescriber’s Digital Reference (PDR)
Hydralazine hydrochloride injection prescribing information, DailyMed (NIH National Library of Medicine) (2022)
Hydralazine hydrochloride tablet prescribing information, DailyMed (NIH National Library of Medicine) (2020)
Hydralazine, StatPearls (2023)
Hydralazine, MedlinePlus (2017)
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