Hydralazine side effects and drug information

Hydralazine is one of the medications that is used to lower blood pressure. It can be taken alone or can be combined with other medicines that also functions the same way. This medication is available with both injection and oral tablets. But the injection must only be given by a medical professional, and no patient is allowed to do it on their own. 

Metabolism Liver
Formula C8H8N4
Trade name BiDil, Apresoline etc
Duration of action 2 to 6 hrs
Onset of action 5 to 30 min
Excretion Urine
Elimination half-life 2–8 hours


One of the good things about Hydralazine is that it is only available as a generic drug thorazine. With this, you can expect that it is cheaper compared to other branded version of this diuretics medication. Hydralazine is part of a demerol drug class that is commonly referred to as peripheral vasodilators. There is no accurate information as to how this medicine treats high blood pressure and heartburn. But some studies say Hydralazine goes directly to the blood vessels and it relaxes them. As a result, a person’s blood pressure can be lowered.

Side Effects of Hydralazine 

Common Side Effects

Like other kinds of medication, Hydralazine can bring side effects to the patient or someone who is taking it. Though oral tablet cannot cause drowsiness, other common side effects that can be experienced are the following:

  • headache
  • loss of appetite
  • nausea
  • vomiting
  • diarrhea
  • fast heart rate
  • chest pain

If these side effects disappear after a few days or weeks, you don’t have to worry. But if they become more serious and discomforts you for a longer time, you have to inform your doctor immediately.

Serious Side Effects

This medication can bring some severe side effects to your body. Below are some of the best examples that you must keep in mind:

Symptoms related to your heart

  1. Very low blood pressure
  2. Fast heart rate
  3. Disorientation or dizziness
  4. Swelling on both arms and legs

Symptoms related to your nerves

  1. Tingling
  2. Numbness
  3. Itching or prickling of your skin

Symptoms related to your mental health

  1. Depression
  2. Anxiety
  3. Changes in your appetite
  4. Feeling worried over things
  5. Uninterested with your normal activities

Symptoms related to allergic reactions

  1. itching skin
  2. redness of your skin
  3. chills
  4. fever
  5. joint pain
  6. skin rashes

If you feel like you are experiencing some of these symptoms, you must ask for a medical emergency because it can lead to a life-threatening situation.

Dosage and Administration

There is no accurate dosage for every person. The form, dose, and frequency of your medication will different in different factors such as:

  • your age
  • your condition
  • other medical conditions
  • reaction on the first dose

But in a common setup, these are the dose available for some people:

Dosage for high blood pressure or hypertension

  • Generic Medicine
  • Form: Oral tablet 
  • Strengths: 10 mg, 25 mg, 50 mg, and 100 mg

Dosage for Adults (18-64 y. o.)

Initial Dosage: an adult will be required to take 10mg orally, about four times a day for two to four days

Adjustment of dosage: Your health care provider might slowly increase your dosage for up to 50mg and must still take four times within the day.

Dosage for Children (1-17 y. o.)

Initial Dosage: a child can take 0.75mg per kg, depending on his or her body weight. The medication is still recommended to be taken orally four times a day.

Adjustment of dosage: Your health care provider may increase the dosage within three to four weeks.

Maximum dosage: a child should only take 7.5mg per kg of his or her weight or 200mg each day

Dosage for Senior (65 y. o. and above)

There is no particular recommendation of dosage for those people aged 65 years and above. Some adults may process drugs slower than the others, and that is normal because of their age. If you are a senior, you are advised to take a lower dosage or a different schedule than an average adult does.

Other things that you should remember while taking Hydrazaline are:

  • Since medication is used for long-term treatment, you have to follow every instruction given to you by your doctor. Failure to follow them might cause a more serious medical risk/s.
  • Take the right dosage prescribed by your medical provider. If you were advised to take 20mg every day, you have to take it all if you want to lower your blood pressure. If you do not comply with this instruction, your blood pressure may stay high and can result in a heart attack or stroke.
  • You should never stop taking Hydralazine suddenly because it can lead to uncontrolled high blood pressure. You might develop various heart problems like a heart attack or chest pain. If you think you need to stop your medication, talk to your doctor, and he will tell you the right way to do it. 
  • Always remember to take medicine as scheduled if you want to maximize its benefits to your body.
  • You can easily tell if the medication is working because your blood pressure is going down. Your doctor will monitor your blood pressure, but it is also recommended that you do it at home so that you can tell if you will continue taking the drug or you will need something else.

Drug Interaction

There is a huge chance that Hydralazine might interact with the other medicines, vitamins, and herbs that you are taking. That’s why you have to tell your doctor about the other drugs like dulcolax that you take so he or she can manage them carefully. You can also minimize the possibility of drug interaction if you choose to purchase all your prescribed medication on the same pharmacy. A pharmacist can help you in determining whether two or more of your drugs can interact with each other. 

The other common drug Flexeril that can interact with the Hydrazaline are:

  1. isocarboxazid
  2. phenelzine sulfate
  3. tranylcypromine sulfate
  4. selegiline

Warnings and Precautions

Allergies are very common when you are taking this medication. Some of them might be trouble with breathing, hives, and swelling of your tongue or throat. If you experience allergic reactions the first time you take this medicine, you should never retake it because it can be fatal or can cause your death.

Warning for Specific Groups 

If you think you are part of any of these groups, you have to be extra cautious with taking Hydrazaline. Be sure that you seek professional advice before you start taking this medication.

  1. A person with heart problems. You must be careful in taking this medication if you have a history of heart problems since it can cause a sudden heart attack. Your doctor will advise you whether Hydralazine will be suitable for your condition or not, so be honest with him.
  2. A pregnant woman. There had been researched on pregnant animals that Hydralazine can bring adverse effects to the fetus if the mother is taking this medicine. Though there are not enough studies that the same effect will be the same to humans, your doctor will only recommend using this medication during pregnancy is the benefits can justify the possible risks to the fetus. 
  3. A woman who is breastfeeding. When a woman feeds her child while taking the medication, there will be a small amount of Hydralazine that will be carried to the breast milk. Although there is no noted effect of the medicine, you still need to inform your doctor that you are breastfeeding your baby.

Overdose and Contraindications

Taking too much of the prescribed dosage of Hydralazine can result in these side effects:

  • very low blood pressure
  • headache
  • irregular heart rate
  • redness to your skin
  • heart attack
  • shock

You have to inform your medical provider immediately if you think you have consumed too much Hydralazine. You might need to visit an emergency room if this happens. 

Medication Guide

Here are some of the best medication guides that can maximize the effect of Hydralazine:

  1. Always take this medicine according to your doctor’s instructions. Never take a higher or lesser dosage, and you should never consume it often than what your doctor has said. 
  2. For more effective medication, you will be advised to control your weight and watch the foods that you are eating every day. If there is a need to change your diet, your doctor can help you with this concern. In some cases, a patient will also be requested to do regular exercise to balance the level of your blood pressure.
  3. Hydralazine is not a cure for your high blood pressure. It is taken to control the level of your blood pressure and to keep it to the normal level. There is a big chance that you will need to take this medicine for the rest of your life if you want to live comfortably. A regular visit to your doctor can help you in determining whether you need to continue taking medicine, or there are some adjustments with your dosage. But the primary goal of this medication is to prevent other serious problems like heart failure, kidney disease, and blood vessel disease.
  4. If you are taking the oral liquid form of this medication, you can mix it with applesauce or fruit juice and immediately consume the mixing. You have to drink all the mixture to get the full dosage of your medication.

Hydralazine is an excellent choice of medication for many people since it is very easy to administer, and you can buy it anywhere at a lower price. But as a patient, you need to be responsible while taking this medicine. Always seek the help of a medical professional to maximize the effects of your medication.