Does hydralazine lower heart rate?

In this article:

• Hydralazine and heart rate
• Hydralazine and bradycardia
• Medications for elevated heart rate
• The bottom line

In this article

• Hydralazine and heart rate
• Hydralazine and bradycardia
• Medications for elevated heart rate
• The bottom line

If you have hypertension, you may be taking a medication like hydralazine hydrochloride (Hcl) to treat it. Hydralazine is a generic medication, also known by the brand name Apresoline, that is FDA approved to treat high blood pressure and certain types of heart failure. It belongs to a class of drugs called vasodilators, which work by relaxing and widening the blood vessels so that blood flows more easily to lower blood pressure.

You might be thinking that since hydralazine lowers blood pressure, it might lower heart rate, too. But that’s not the case. On the contrary, the medication can actually raise heart rate in some people. Read on to get the scoop on how hydralazine works, its impact on heart rate, and more.

Does hydralazine affect heart rate?

It can. While hydralazine itself does not lower heart rate, it may increase it—although indirectly. Its main action is to relax the smooth muscle cells of blood vessels, causing them to expand and, in turn, lower blood pressure. However, this drop in blood pressure can trigger compensatory mechanisms in the body.

“Hydralazine relaxes blood vessels, which can cause blood pressure to drop. In response, the body may try to compensate by increasing the heart rate, a reaction called reflex tachycardia,” says Mary Abed, MD, a board-certified cardiologist and Medical Director at  RWJBarnabas Health Medical Group in Jersey City, New Jersey. She says it’s possible to experience heart palpitations and heart pounding or racing after taking hydralazine as the body tries to make up for the sudden drop in blood pressure.

In other words, when hydralazine lowers blood pressure, the body senses this drop, activating the sympathetic nervous system, which is associated with the “flight or flight” response. Think of it as your body’s way of saying, “Whoa, we need to keep things balanced here!” As a result, your heart starts beating a bit faster so that blood keeps circulating to vital organs and tissues. 

In general, hydralazine can enhance cardiac output by decreasing afterload—the resistance the heart faces when pumping blood—which can be beneficial in the context of heart failure. According to a study published in the journal Circulation, this effect contributes to hydralazine’s effectiveness in increasing cardiac output (the amount of blood the heart pumps per minute) among hypertensive patients experiencing congestive heart failure.  

Common side effects of hydralazine include:

• Flushing
• Skin rash or hives
• Headache
• Nausea or vomiting
• Loss of appetite
• Diarrhea or constipation
• Eye tearing
• Stuffy nose

Serious side effects that warrant immediate medical attention include:

• Fainting
• Muscle or joint pain
• Fever
• Fast heart rate
• Chest pain/angina
• Shortness of breath
• Tiredness
• Swollen feet or ankles
• Numbness or tingling in hands or feet

Hydralazine is contraindicated in patients with coronary artery disease, mitral valvular rheumatic heart disease, and those who have experienced an allergic reaction to the medication. Hydralazine should be used with caution in individuals with kidney disease and those taking medications in the MAO inhibitor family. Pregnant and breastfeeding women should consult their healthcare provider about the safety of hydralazine.

For adults with hypertension, the dosage is 200 to 400 mg of oral solution daily, divided into two to four doses, or 10 to 50 mg four times daily. If you miss a dose, take it as soon as possible unless it’s close to your next dose—in that case, skip the missed dose and go back to the dosing schedule provided by your healthcare provider.

In some instances, it may be best not to take hydralazine after 6 p.m. Dr. Abed says the medication can cause dizziness and a racing heart, which may be more noticeable at night. Although taking it earlier in the day helps your body adjust while awake and active, it may necessitate evening doses if your healthcare provider instructs you to take it multiple times a day. 

Taking hydralazine with bradycardia

Bradycardia, defined as having a heart rate that is less than 60 beats per minute, can cause complications when using hydralazine. “If you already have a slow heart rate, taking hydralazine might make your heart work harder to compensate for the drop in blood pressure if your heart rate doesn’t increase,” says Dr. Abed, adding that dizziness, fainting, or an irregular heartbeat may occur as symptoms of reduced cardiac output.

Although hydralazine is not outright contraindicated for individuals with bradycardia, caution is warranted. Dr. Abed advises consulting your healthcare provider if symptoms of dizziness, fainting, or an irregular heartbeat develop when taking the drug with bradycardia. 

“When considering any medication treatment, even over-the-counter medication, it’s always good to consult with your family physician, who knows your medical history the best,” urges Mike Sevilla, MD, a board-certified primary care physician at Salem Family Care in Salem, Ohio. They can assess your health situation, advise you of possible drug interactions, and formulate an individualized treatment plan tailored to your needs, making medication adjustments as needed to avoid unwanted complications.

What medications can treat an elevated heart rate?

According to Dr. Abed, several classes of medications can be used to treat an elevated heart rate and are chosen based on the underlying cause. Your provider can determine the best prescription medication based on your unique needs, including the following:

• Beta blockers, like metoprolol, atenolol, and propranolol, block the effects of adrenaline on the heart to reduce heart rate and decrease blood pressure.
• Calcium channel blockers, such as diltiazem and verapamil, prevent calcium from entering the cells of the heart and blood vessels, reducing heart rate and enhancing blood flow.
• Antiarrhythmic drugs, including amiodarone and sotalol, help restore and stabilize a normal heart rhythm.

Dr. Sevilla notes that beta blockers and calcium channel blockers are not recommended for patients with bradycardia because they significantly slow down the heart rate, potentially causing a dangerously low heart rhythm which can cause circulatory collapse.

The bottom line

Hydralazine is not a medication designed to lower heart rate, and in fact, it may lead to an increase in heart rate due to the reflex tachycardia that can follow a decrease in blood pressure. If you are experiencing an elevated heart rate on hydralazine, seek medical advice from a qualified healthcare professional who may recommend alternative medications targeted at managing this condition. Always engage with your healthcare provider to develop a personalized treatment plan that aligns with your health needs.