Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes Hydralazine. If you are concerned about side effects, discuss the risks and benefits of Hydralazine with your doctor.

The following side effects have been reported by at least 1% of people taking Hydralazine. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• blurred vision
• chest pain
• Constipation
• decreased appetite
• Diarrhea
• dizziness
• fast heart rate
• Fever
• flushing
• headache
• Low Blood Pressure (e.g., fainting, dizziness, lightheadedness, blurred vision, nausea)
• muscle cramps
• nasal congestion
• nausea
• pounding heartbeat
• rash
• stomach upset
• tremor

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• fluid retention (e.g., swelling of the feet, ankles, or lower leg)
• increased frequency of infections
• shortness of breath
• signs of Anemia (low red blood cells; e.g., dizziness, pale skin, unusual tiredness or weakness, shortness of breath)
• signs of heart problems (e.g., fast, irregular heartbeat or pulse, chest pain, sudden weight gain, difficulty breathing, leg swelling)
• signs of kidney problems (e.g., change in the amount or colour of urine, increased urination at night, blood in the urine, swelling in the feet or legs)
• symptoms of Angina (e.g., chest pain, sudden wheeziness, difficulty breathing, or shortness of breath)
• symptoms of liver problems (e.g., nausea, loss of appetite, yellowing of the skin and eyes, abdominal pain, dark urine)
• unexplained joint pain with fever and skin rash
• unusual tiredness

Stop taking the medication and seek immediate medical attention if any of the following occur:

• symptoms of a serious allergic reaction (such as Hives; swelling of the face, eyes, and throat; and difficulty breathing)
• symptoms of lupus (e.g., joint pain, fever, generalized rash)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking Hydralazine.

10 mg
Each orange, round, scored tablet, debossed with "H" on one side and "38" on the other side, contains 10 mg of hydralazine. Nonmedicinal ingredients: anhydrous lactose, microcrystalline cellulose, sodium starch glycolate, stearic acid, and FD&C Yellow No. 6.

25 mg
Each orange, round, unscored tablet, debossed with "H" on one side and "39" on the other side, contains 25 mg of hydralazine. Nonmedicinal ingredients: anhydrous lactose, microcrystalline cellulose, sodium starch glycolate, stearic acid, and FD&C Yellow No. 6.

50 mg
Each orange, round, unscored tablet, debossed with "H" on one side and "40" on the other side, contains 50 mg of hydralazine. Nonmedicinal ingredients: anhydrous lactose, microcrystalline cellulose, sodium starch glycolate, stearic acid, and FD&C Yellow No. 6.

Do not use hydralazine if you:

• are allergic to hydralazine or any ingredients of the medication
• have an untreated Aneurysm in the aorta (large artery leaving the heart)
• have certain heart conditions (e.g., aortic stenosis, mitral stenosis, constrictive pericarditis, cor pulmonale, or a very fast heartbeat combined with heart failure)
• have Coronary Artery Disease
• have Lupus (also called systemic lupus erythematosus or SLE)
• have mitral valve rheumatic heart disease

There may be an interaction between hydralazine and any of the following:

• Aldesleukin
• Aliskiren
• alpha-agonists (e.g., Clonidine, methyldopa)
• alpha-blockers (e.g., Alfuzosin, Doxazosin, Tamsulosin)
• amifostine
• Amiodarone
• amphetamines (e.g., Dextroamphetamine, Lisdexamfetamine)
• angiotensin converting enzyme inhibitors (ACEIs; Captopril, Enalapril, Ramipril)
• angiotensin receptor blockers (ARBs; e.g., Candesartan, Irbesartan, Losartan)
• antipsychotics (e.g., Aripiprazole. Chlorpromazine, Lurasidone, Paliperidone, Quetiapine)
• barbiturates (e.g., butalbital, pentobarbital, Phenobarbital)
• beta-adrenergic blockers (e.g., Atenolol, Propranolol, Sotalol)
• brimonidine
• calcium channel blockers (e.g., Amlodipine, Diltiazem, Nifedipine, Verapamil)
• dexmethylphenidate
• diuretics (water pills; e.g., Furosemide, Hydrochlorothiazide, triamterene)
• Duloxetine
• Guanfacine
• levodopa
• Methylphenidate
• Minoxidil
• monoamine oxidase inhibitors (M.O.S. e.g., Moclobemide, Rasagiline, Selegiline, Tranylcypromine)
• Morphine
• nitrates (e.g., Nitroglycerin, isosorbide dinitrate, isosorbide mononitrate)
• non-steroidal anti-inflammatory medications (NSAIDs; e.g., Diclofenac, Ibuprofen, Naproxen)
• Obinutuzumab
• Pentoxifylline
• phosphodiesterase 5 inhibitors (e.g., Sildenafil, Tadalafil, Vardenafil)
• quinine
• Rotigotine
• sacubitril
• sotalol
• Tizanidine
• tolcapone

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with Hydralazine. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications that you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the Nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.

Before you begin taking a medication, be sure to inform your doctor of any medical conditions or Allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should take Hydralazine.

Blood tests: Rarely, Hydralazine can decrease the number of neutrophils (a type of white blood cell that helps fight infection), red blood cells (which carry oxygen), and platelets (which help your blood to clot). Your doctor will do regular blood tests to monitor your blood cell levels while you are taking Hydralazine.

Kidney Disease: Decreased kidney function can cause Hydralazine to build up in the body, causing side effects. If you have decreased kidney function, discuss with your doctor how Hydralazine may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Hydralazine, and whether any special monitoring is needed.

Liver function: Liver disease or reduced liver function may cause Hydralazine to build up in the body, causing side effects. If you have liver problems, discuss with your doctor how Hydralazine may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Hydralazine, and whether any special monitoring is needed. Your doctor may want to test your liver function regularly with blood tests while you are taking Hydralazine.

Low blood pressure: Some people taking hydralazine may experience sudden blood pressure drops when getting up from a sitting or lying position. These blood pressure drops could lead to dizziness, lightheadedness, and falls. If you experience this problem, try getting up more slowly. If it persists or if you faint, contact your doctor.

Lupus: Hydralazine may cause lupus-like symptoms (e.g., joint pain, fever, generalized rash). If these symptoms develop, contact your doctor immediately.

Pregnancy: Hydralazine should only be used during pregnancy when the benefits outweigh the risks. If you become pregnant while taking Hydralazine, contact your doctor immediately.

Breast-feeding: Hydralazine passes into breast milk. If you are a breast-feeding mother and are taking hydralazine, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using Hydralazine have not been established for children.

Seniors: Seniors may be more sensitive to the blood-lowering effects of hydralazine. It should be used with more caution.

Hydralazine belongs to the class of medications called vasodilators. It is used alone or with other medications to reduce blood pressure. It works to lower blood pressure by relaxing veins and arteries.

Hydralazine may be available under multiple brand names and/or in several different forms. Any specific brand name of Hydralazine may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of Hydralazine may not be used for all of the conditions discussed here.

Your doctor may have suggested Hydralazine for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking Hydralazine, speak to your doctor. Do not stop taking Hydralazine without consulting your doctor.

Do not give Hydralazine to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take Hydralazine if their doctor has not prescribed it.