Diltiazem: Everything You Need to Know About This Drug

Old man exercising
  • Diltiazem is a medication used to treat angina, high blood pressure, and abnormal heart rhythms.

  • Some side effects of diltiazem include lower blood pressure, reduced stamina, and heart palpitations.

  • Always keep track of your side effects and seek emergency medical attention if you have trouble breathing or experience any other adverse reactions.

  • Never make adjustments to your diltiazem dosage and call your doctor if you’ve skipped a dose.

Diltiazem is a key drug used to manage certain health conditions and it may be exactly what you need if you’re one of the 119.9 million Americans living with high blood pressure.

After its approval for use in the U.S. in 1982, millions of diltiazem prescriptions are filled each year — but what exactly is diltiazem?

What is Diltiazem?

Diltiazem – pronounced dul-tie-uh-zem – is a medication called a calcium channel blocker.

It's used to treat hypertension, angina (chest pain caused by decreased blood flow to the heart muscle) — including Prinzmetal’s Angina, and certain tachyarrhythmias (fast, abnormal heart rhythms).

Calcium channel blockers, as the name suggests, obstruct calcium channels. These channels are found in the lining outside the muscle cells in the heart and inside blood vessels.

Key Point: What is Prinzmetal’s Angina?
  • This condition is caused by abnormal spasms of the coronary arteries supplying the heart muscle with blood.

  • These spasms cause the crushing or pressing chest pain typical of angina.

  • Changes like these are significant enough to be read on an electrocardiogram (EKG). Placing nitrites under the tongue can reverse them.

What does calcium have to do with blood pressure and angina?

Blood pressure is regulated by three main factors: heart rate, the volume of each pump of the heart, and the resistance the arteries have against the force of the heart pumping.

The main pipes leading away from the heart are known as arteries. These are thick vessels that transport blood throughout the body where it is needed, (including to the heart muscle itself).

Arteries have muscles in their walls that contract to regulate how much blood can flow through them. When the muscles in these vessels contract, arteries become smaller, and less blood flows through them.

As arteries grow narrower, the pressure inside them goes up. It's like squeezing a garden hose: even though less water comes out, the force of the water is stronger.

Calcium is responsible for the contraction of the muscle cells in these blood vessels. Diltiazem blocks the calcium channels in arteries, preventing them from narrowing. When the pressure in these vessels decreases, blood pressure is lowered.

During this process, heart muscle contraction is also decreased, which further reduces blood pressure.

The heart needs its own blood supply, which it gets from coronary arteries. Blocking calcium channels relaxes these arteries, allowing more blood to flow to the heart.

This helps ease chest pain from angina caused by reduced blood flow. Diltiazem also slows the heart rate, giving the heart more time to receive blood, further helping to relieve the pain of angina.

Diltiazem and Arrhythmias

Diltiazem decreases heart rate and therefore directly corrects fast rhythms. By decreasing the heart rate, it also decreases the heart's need for oxygen.

Compare this to a runner doing a sprint: the faster they run, the harder they breathe.

Their bodies are using more oxygen because they are moving faster and burning more energy. The heart works in the same way.

By slowing down the heart rate, diltiazem reduces the heart's demand for oxygen. This naturally causes it to beat more slowly.

Diltiazem is typically only used for fast atrial fibrillation and paroxysmal supraventricular tachycardia (PSVT).

What Should You Tell Your Doctor Before Taking Diltiazem?

Diltiazem is a prescription drug, so your doctor will take your medical history before they prescribe it.

They will ask you a series of questions to determine whether this drug is the appropriate treatment for you.

You will typically need to provide the following information:

  • Any existing health problems you have, especially cardiovascular diseases
  • Previous serious illnesses, particularly strokes and heart attacks
  • Medication allergies
  • Medications you are currently taking, including over-the-counter medications

What Should You Know Before Taking Diltiazem?

Diltiazem is a complex medication that impacts various parts of the body. As mentioned above, it decreases blood pressure by multiple mechanisms.

It’s important to tell your doctor about any other medications you are using, as these often have overlapping functions.

This can cause blood pressure to drop too far and cause several unpleasant side effects which we’ll discuss later on.

What does diltiazem do to your heart rate?

Diltiazem decreases heart rate. It affects the natural pacemaker of the heart which then instructs the rest of the heart to pump slower.

This type of medication is called a “negative chronotrope” (chrono referring to time), meaning it decreases the speed of the heart.

Special dietary requirements

There are no routine dietary requirements for using diltiazem. That said, people using these medications often have other health problems which require a special diet to manage.

People who use diltiazem may have one or more of the following conditions:

  • High blood pressure
  • High cholesterol
  • Obesity
  • Gout
  • Diabetes mellitus
  • Coronary heart disease

These conditions are all lifestyle-related disorders and may occur together or in some combination. Each of these should be treated individually and may require their own diets.

Keep in mind that diltiazem is a medication for high blood pressure. Consuming a diet rich in sodium, particularly added salt, can exacerbate blood pressure issues.

Your doctor may discuss any dietary requirements that are applicable to you. Getting advice from a dietician can also help you make better nutritional choices.

Medication interactions

Also known as drug interactions, medication interactions refer to the changes that can occur when the effect of one drug is altered by the presence of another drug, food, drink, or chemical in the environment.

These interactions can enhance, reduce, or even neutralize the effectiveness of one or both drugs. They can also increase the risk of side effects.

  • Below is a list of medications that should be avoided entirely while you’re taking diltiazem, unless otherwise instructed by your healthcare provider:
  • Dantrolene (muscle relaxant)
  • Flibanserin (medication to treat hypoactive sexual desire disorder)
  • Lomitapide (cholesterol-lowering medication — however, not all cholesterol-lowering medication has interactions with diltiazem)
  • Lonafarnib (used to treat an extremely rare aging disorder)
  • Pimozide (antipsychotic medication)
Key Point: What are Some Popular Diltiazem Brands in the U.S.?

The availability of specific brands may vary based on region and pharmacy stock. Always consult with your doctor or pharmacist for the most current information.

Here are some of the popular brands used in the U.S.:

  • Cardizem®
  • Dilacor®
  • Tiazac®
  • Cartia XT®
  • Taztia XT®

How Should I Use Diltiazem?

You should always use diltiazem as directed by your healthcare provider.

The drug is available in different strengths and forms, including tablets, capsules, and injectable solutions that are typically administered in hospital settings.

Depending on the condition being treated, your overall health, and your current medications, your doctor will prescribe the appropriate dose and formulation of diltiazem.

What should I do if I miss a dose of diltiazem?

Always call your doctor for advice. If you’ve missed a dose, your blood pressure will typically need to be rechecked.

The medication will be continued on your next dose if your blood pressure is not significantly raised.

Who Should Not Be Using Diltiazem?

Diltiazem is an effective calcium channel blocker, but it may not work for certain people. Your doctor will not prescribe diltiazem if you have one or more of the following:

  • Allergies (consider wearing medical ID tags listing your allergies
  • Systolic blood pressure of less than 90 mm Hg
  • Certain heart block types
  • Recent or current heart attacks
  • Previous or severe side effects from this medication
Key Point: Pregnancy Risks and Diltiazem

It's crucial to inform your doctor if you are pregnant, planning to become pregnant, or breastfeeding, as the medication may impact the fetus or nursing child.

Diltiazem is considered a Pregnancy Category C drug by the Food and Drug Administration (FDA). While no human studies were conducted, animal trials indicated instances of stillbirths.

It should therefore only be administered to pregnant women if the potential benefit is greater than the risks. Nursing mothers should use alternative feeding methods, as diltiazem may pass into human breast milk.

What are the Common Side Effects of Diltiazem?

Whenever you start taking a new medication, your doctor or pharmacist will typically explain what side effects you can expect.

Keep a record of your side effects and tell your doctor if they worsen over time. They may need to adjust your dose or provide alternative medication options if diltiazem is not working for you.

Common side effects include:

  • Reduced stamina or inability to exercise for prolonged periods
  • Irregular or rapid heartbeats (palpitations)
  • Decreased blood pressure, sometimes causing dizziness or lightheadedness
Husband feeling his heart

What are Some Serious Side Effects of Diltiazem?

Should you experience any of the following severe side effects, call your doctor immediately, or dial 911 and get emergency medical assistance:

  • Swelling, especially in the legs. This is known as pitting edema. To identify pitting edema, press on the swollen area, such as the font of the calf, for about 10 seconds. If a dent remains after releasing the pressure, you have edema.
  • Slow heart rate known as bradycardia (less than 60 beats per minute)
  • Fainting (syncope)
  • Allergic reactions
  • Hypotension (severely low blood pressure)
  • Worsening of preexisting heart failure
Key Point: What Should I Do if I’ve Overdosed on Diltiazem?

If you suspect you’ve overdosed on diltiazem, immediately call an ambulance for transfer to your emergency department. Don’t try to drive yourself to the hospital in this condition, as you may faint behind the wheel.

Call anyone nearby for help, tell them what happened, and ask them to wait with you until the ambulance arrives.

Here are some more tips to follow in case of an overdose:

  • Don’t take anything to "cancel out" the medication's effects
  • Refrain from standing or sitting upright. If you’re dizzy, lie down with your feet raised
  • Be aware of potential injuries caused by a drop in blood pressure
  • Do not take any more blood pressure medication without consulting a healthcare provider
  • Always prioritize going to the hospital, even if you feel fine

It’s also good to keep a list of other medications you take at hand as this makes it easier for healthcare professionals to treat you in case of a suspected overdose.

What are Some Diltiazem Alternatives?

This largely depends on your reason for using this medication. Like any other antiarrhythmic drug or blood pressure medicine, diltiazem is only available with a prescription.

Sometimes, people experiencing chest pain may take 162–325 mg of chewable aspirin while awaiting transfer to the hospital.

This kind of treatment is reserved for when you have heart attack concerns, and this advice is usually given by a paramedic or their dispatcher.

Diltiazem is often a first-choice treatment for high blood pressure. Other blood pressure medications include beta blockers, diuretics, ACE inhibitors, ARBs, alpha-blockers, and other calcium channel blockers.

Some people might need a combination of medications or a multi-drug tablet. Always follow your doctor's guidance and never adjust your own medication.

Where Can I Get a Prescription for Diltiazem?

Do you need treatment for hypertension or one of the other conditions mentioned in our article? LifeMD can help.

LifeMD can connect you to a licensed medical professional who can prescribe diltiazem or offer alternative treatment recommendations that may be more suitable for you. Book your appointment today.

LifeMD makes it easy to stay on top of your health because talking to a doctor, filling your prescriptions, getting your labs done—and more—are all easy and cost-effective. Come discover a healthcare solution built around you and your life.

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This article is intended for informational purposes only and should not be considered medical advice. Consult a healthcare professional or call a doctor in the case of a medical emergency.

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