Generic name: hydralazine [ hye-DRAL-a-zeen ]
Drug class: Vasodilators
Medically reviewed by Drugs.com. Last updated on Oct 19, 2022.
Uses for hydralazine
Hydralazine is used to treat high blood pressure (hypertension). It is also used to control high blood pressure in a mother during pregnancy (pre-eclampsia or eclampsia) or in emergency situations when blood pressure is extremely high (hypertensive crisis).
High blood pressure adds to the workload of the heart and arteries. If it continues for a long time, the heart and arteries may not function properly. This can damage the blood vessels of the brain, heart, and kidneys, resulting in a stroke, heart failure, or kidney failure. Lowering blood pressure can decrease the risk of heart attacks and strokes.
Hydralazine works by relaxing the blood vessels and increasing the supply of blood and oxygen to the heart while reducing its workload.
This medicine is available only with your doctor's prescription.
Before using hydralazine
In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:
Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Appropriate studies on the relationship of age to the effects of hydralazine have not been performed in the pediatric population. However, no pediatric-specific problems have been documented to date.
No information is available on the relationship of age to the effects of hydralazine in geriatric patients.
Studies in women suggest that this medication poses minimal risk to the infant when used during breastfeeding.
Interactions with Medicines
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your healthcare professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine.
Interactions with Food/Tobacco/Alcohol
Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using this medicine with any of the following may cause an increased risk of certain side effects but may be unavoidable in some cases. If used together, your doctor may change the dose or how often you use this medicine, or give you special instructions about the use of food, alcohol, or tobacco.
- Enteral Nutrition
Other Medical Problems
The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:
- Angina (severe chest pain) or
- Blood disease or
- Heart attack, history of or
- Heart rhythm problems or
- Hypotension (low blood pressure) or
- Peripheral neuritis (nerve problem) or
- Stroke, history of or
- Systemic lupus erythematosus—Use with caution. May make these conditions worse.
- Coronary artery disease or
- Mitral valvular rheumatic heart disease—Should not be used in patients with these conditions.
- Kidney disease—Use with caution. The effects may be increased because of slower removal of the medicine from the body.
- Phenylketonuria—The oral solution contains aspartame, which can make this condition worse.
Proper use of hydralazine
Take this medicine exactly as directed by your doctor. Do not take more or less of it, and do not take it more often than your doctor ordered. Your dose may need to be changed several times in order to find out what works best for you.
In addition to the use of this medicine, treatment for your high blood pressure may include weight control and changes in the types of foods you eat, especially foods high in sodium (salt). Your doctor will tell you which of these are most important for you. You should check with your doctor before changing your diet.
Many patients who have high blood pressure will not notice any signs of the problem. In fact, many may feel normal. It is very important that you take your medicine exactly as directed and that you keep your appointments with your doctor even if you feel well.
Remember that this medicine will not cure your high blood pressure, but it does help control it. You must continue to take it as directed if you expect to lower your blood pressure and keep it down. You may have to take high blood pressure medicine for the rest of your life. If high blood pressure is not treated, it can cause serious problems such as heart failure, blood vessel disease, stroke, or kidney disease.
It is best to take your medicine on an empty stomach, 1 hour before or 2 hours after meals.
For patients taking the oral liquid:
- The oral solution may be mixed with fruit juice or applesauce. If mixed with fruit juice or applesauce, take immediately after mixing. Be sure to take all of the mixture to get the full dose of the medicine.
The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
- For high blood pressure:
- For oral dosage form (oral solution):
- Adults—40 to 200 milligrams (mg) per day, divided into two or four doses.
- Children—Dose is based on body weight and must be determined by your doctor. The dose is usually 0.75 to 7.5 milligram (mg) per kilogram (kg) of body weight per day, divided into two or four doses.
- For oral dosage form (tablets):
- Adults—At first, 10 milligrams (mg) four times a day. Your doctor may adjust your dose as needed. However, the dose is usually not more than 50 mg four times a day.
- Children—Dose is based on body weight and must be determined by your doctor. The starting dose is usually 0.75 milligram (mg) per kilogram (kg) of body weight per day, divided into four doses. The doctor may adjust the dose as needed. However, the dose is usually not more than 7.5 mg per kg of body weight per day or 200 mg per day.
- For oral dosage form (oral solution):
If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.
Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.
Keep out of the reach of children.
Do not keep outdated medicine or medicine no longer needed.
Ask your healthcare professional how you should dispose of any medicine you do not use.
Precautions while using hydralazine
It is important that your doctor check your progress at regular visits to make sure that this medicine is working properly. Blood tests may be needed to check for unwanted effects.
Hydralazine may cause some people to have headaches or to feel dizzy. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are dizzy or not alert.
Do not take other medicines unless they have been discussed with your doctor. This especially includes over-the-counter (nonprescription) medicines for appetite control, asthma, colds, cough, hay fever, or sinus problems, since they may tend to increase your blood pressure.
Side Effects of hydralazine
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur:
- Arm, back, or jaw pain
- chest pain or discomfort
- chest tightness or heaviness
- fast, pounding, or irregular heartbeat or pulse
- shortness of breath
- Black, tarry stools
- blindness or vision changes
- blisters on the skin
- blurred vision
- burning of the face or mouth
- burning, crawling, itching, numbness, painful, prickling, "pins and needles", or tingling feelings
- clumsiness or unsteadiness
- difficult or labored breathing
- dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
- fever and sore throat
- general feeling of discomfort or illness or weakness
- joint pain
- lower back or side pain
- muscle pain
- numbness, tingling, pain, or weakness in the hands or feet
- painful or difficult urination
- pale skin
- shakiness in the legs, arms, hands, or feet
- skin rash or itching
- swelling of the feet or lower legs
- swollen, painful, or tender lymph glands in the neck, armpit, or groin
- tightness in the chest
- trembling or shaking of the hands or feet
- ulcers, sores, or white spots in the mouth
- unusual bleeding or bruising
- unusual tiredness or weakness
- weakness in hands or feet
- Dark urine
- light-colored stools
- upper right abdominal or stomach pain
- yellow eyes and skin
Get emergency help immediately if any of the following symptoms of overdose occur:
Symptoms of overdose
- Feeling of warmth
- redness of the face, neck, arms, and occasionally, upper chest
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
- loss of appetite
- weight loss
- difficulty with moving
- feeling anxious or depressed
- muscle cramps, pain, or stiffness
- pain in the joints
- rash, hives, welts, or itching
- stuffy nose
- watery eyes
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
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