Hydralazine can cause side effects, although not everyone who takes it will have problems. The most common effects are linked to how the medicine relaxes blood vessels and lowers blood pressure. This can lead to symptoms such as headache, dizziness, flushing, nausea, and a faster heartbeat.
Most mild side effects improve as the body adjusts to treatment. Some reactions need more attention, especially if they are severe, persistent, or appear with other unusual symptoms.
Common Hydralazine Side Effects
The most common side effects of hydralazine include:
- Headache
- Dizziness
- Nausea
- Vomiting
- Flushing
- Fast heartbeat
- Palpitations
- Weakness
- Loss of appetite
These effects can be more noticeable when treatment starts or when the dose is increased.
Dizziness may happen because hydralazine lowers blood pressure. Standing up quickly can make this feeling worse. Moving slowly from a sitting or lying position may help.
Why Does Hydralazine Cause Headaches?
Hydralazine widens blood vessels. This change in blood vessel tone can trigger a headache in some people.
A mild headache may improve as the body becomes used to the medicine. If headaches are severe, persistent, or different from what you normally experience, contact your healthcare professional.
Can Hydralazine Cause Dizziness?
Yes. Dizziness is a possible side effect of hydralazine.
Because the medicine lowers blood pressure, some people may feel lightheaded, especially after standing up. This can also happen if blood pressure falls too much.
If dizziness keeps happening, tell your healthcare professional. Do not change your dose on your own.
Can Hydralazine Cause a Fast Heartbeat?
Yes. Hydralazine can cause a faster heart rate or palpitations.
The medicine relaxes arteries and lowers blood pressure. In response, the body may increase the heart rate to help maintain blood flow. This is called reflex tachycardia.
A mild increase in heart rate may occur during treatment, but a persistent or uncomfortable racing heartbeat should be discussed with a healthcare professional.
Can Hydralazine Cause Nausea?
Nausea can occur while taking hydralazine. Some people may also experience vomiting or a reduced appetite.
If nausea is severe, lasts for a long time, or makes it difficult to eat and drink normally, speak with your healthcare professional.
Serious Hydralazine Side Effects
Serious reactions are less common but can occur.
One important reaction is a lupus-like syndrome. This is an immune reaction that can develop with hydralazine, especially with prolonged treatment or higher doses.
Possible symptoms include:
- Joint or muscle pain
- Fever
- Unusual tiredness
- Chest pain that worsens with deep breathing
- Skin rash
- Swollen or painful joints
These symptoms can have many causes, so they do not automatically mean hydralazine is responsible. New or unexplained symptoms should be checked by a healthcare professional.
Can Hydralazine Cause Low Blood Pressure?
Yes. Hydralazine is designed to lower blood pressure, but in some people the pressure can fall too much.
Signs may include:
- Severe dizziness
- Weakness
- Blurred vision
- Feeling faint
- Fainting
If you faint or have severe symptoms, seek medical care promptly.
People taking hydralazine with other blood pressure medicines may need closer monitoring because the combined effects can lower blood pressure further.
Can Hydralazine Cause Swelling?
Swelling, especially in the feet or ankles, can occur during hydralazine treatment.
Swelling can have many possible causes, including other medicines and heart or kidney problems. New or worsening swelling should be discussed with a healthcare professional rather than assumed to be a harmless side effect.
Swelling combined with shortness of breath or rapid weight gain needs prompt medical attention.
Rare but Important Reactions
Rare reactions can affect the kidneys, liver, nerves, or blood cells.
Warning signs can include unusual bruising or bleeding, yellowing of the skin or eyes, dark urine, severe weakness, numbness, or other unexplained changes.
These symptoms do not occur in most people taking hydralazine. They should still be reported because they may need medical evaluation.
Who May Have a Higher Risk of Side Effects?
The risk of side effects can depend on the dose, length of treatment, other medicines, and overall health.
People taking several medicines that lower blood pressure may be more likely to experience dizziness or low blood pressure.
Long-term use and higher doses of hydralazine can also increase the risk of certain immune-related reactions. Your healthcare professional may monitor you based on your treatment plan and health needs.
What Should You Do If Hydralazine Causes Side Effects?
Do not stop hydralazine suddenly or change the dose without medical advice.
For mild symptoms, keep track of when they occur and whether they follow a dose. This information can help your healthcare professional decide whether the medicine, dose, or timing needs review.
Severe symptoms require prompt medical attention. Seek urgent care for fainting, chest pain, severe breathing problems, a severe or irregular heartbeat, or other serious symptoms.
When Should You Contact a Healthcare Professional?
Contact your healthcare professional if side effects are persistent, becoming worse, or interfering with daily activities.
Seek urgent medical help if you experience fainting, severe chest pain, serious breathing difficulty, or a severe or persistent abnormal heartbeat.
New joint pain, fever, rash, unusual weakness, or other symptoms that could suggest an immune reaction should also be evaluated.
The Bottom Line
Hydralazine side effects can include headache, dizziness, nausea, flushing, weakness, and a faster heartbeat. These effects are often related to the medicine’s blood vessel and blood pressure effects.
More serious reactions are less common but can include a lupus-like immune reaction and problems related to very low blood pressure. If you develop severe symptoms or unusual changes while taking hydralazine, contact a healthcare professional promptly.
References
- Hydralazine side effects, warnings, and precautions — MedlinePlus
- Hydralazine hydrochloride prescribing information and adverse reactions — DailyMed
- Drug-induced lupus: symptoms and causes — National Institute of Arthritis and Musculoskeletal and Skin Diseases
Medical Disclaimer
This content is for educational purposes and does not replace medical advice. Hydralazine should be taken only as prescribed. Speak with a healthcare professional about persistent or concerning side effects.