If you’ve got high blood pressure (hypertension) or angina, which is a type of chest pain caused by reduced blood flow to the heart, your health care provider may prescribe diltiazem ER (brand name: Cardizem CD). If you’re about to start this medication, we bet you have a whole bunch of questions about how it works and what you can expect. The good news? Danielle Plummer, PharmD, a pharmacist in Las Vegas and CEO of HG Pharmacist Consulting, has the answers that will help you understand the ins and outs of this important medication.

Question: Why did my doctor choose diltiazem ER?

Plummer: While there are a several medications that treat high blood pressure, your physician may have prescribed diltiazem ER if you did not respond to or could not tolerate the side effects of a previous drug for high blood pressure. Or it may have been added to a blood pressure medication you’re already taking. It’s also a common choice for patients who also have kidney disease, because it’s metabolized through the liver, not the kidneys, making it a safer option.

Calcium channel blockers, including diltiazem ER, are often paired with a diuretic (or water pill) as part of a first-line combination therapy for Black individuals and people with diabetes, according to the latest guidelines from the International Society of Hypertension.

Question: How does diltiazem ER work?

Plummer: This medication is a calcium channel blocker, which helps prevent the calcium ions in your body from moving into the cells of the heart and blood vessels. Calcium ions make your heart forcefully contract — and by blocking them, diltiazem ER relaxes and widens your blood vessels. That means your heart doesn’t have to work as hard to pump blood to all parts of your body. This, in turn, allows blood to flow more easily. Diltiazem ER also lowers your heart rate and quells your heart’s demand for oxygen, which lowers blood pressure and reduces symptoms of angina.

Question: Why is this important?

Plummer: When left untreated, high blood pressure can damage many parts of your body, including the brain, heart, blood vessels, kidneys and more. This can lead to heart disease, a heart attack, heart failure, stroke, kidney failure, loss of vision and other serious health problems. Meanwhile, angina (or chest pain) can lead to a heart attack, if it’s not dealt with.

Question: How do I take diltiazem ER?

Plummer: The “ER” in diltiazem ER stands for “extended release,” which means that the medication slowly releases into your system, allowing you to take the tablet or capsule just once daily. You should always take diltiazem ER on an empty stomach, meaning about one hour before a meal or two hours after a meal. This is crucial because food affects your body’s metabolism of the medication, potentially increasing the amount in your system, which can lead to an increased response and increased side effects.

Need help paying for your diltiazem ER prescription? Download a coupon now and use it at your local pharmacy.

Question: Can I crush diltiazem ER to make it easier to swallow?

Plummer: No, you should not cut, crush or chew diltiazem ER tablets. If you have capsules, however, you can open one up and spread it into applesauce, but do not chew the medicine.

Question:  Do I take diltiazem ER to treat angina when it occurs?

Plummer: No. Diltiazem ER needs to be taken regularly to prevent angina. It’s not designed to treat an angina attack as it’s occurring. Other meds, like nitroglycerin placed under the tongue, do that.

Question: Should anyone avoid diltiazem ER?

Plummer: Don’t take diltiazem ER if you’re on a beta-blocker. The same holds true for individuals with heart failure with reduced ejection fraction, which is when the heart is not pumping as it should. Diltiazem ER could worsen your condition. Also, people with liver disease need to use caution. This medication is metabolized mainly through the liver and has been shown to increase liver enzymes.

If you’re pregnant, diltiazem ER should only be used if there are no other viable replacement medications. And nursing moms should also talk to a health care professional about possibly avoiding diltiazem ER, since it has been shown to pass into breast milk.

Question: How long before I’ll see a change?

Plummer: Most people with high blood pressure don’t actually feel sick, which means you’re not going to notice any immediate changes. Instead, it’ll likely be about 2 to 4 weeks before you’re able to get your blood pressure under control. And this time frame is a good thing: It’s really important not to drop blood pressure too quickly, or the adverse effects will outweigh the benefits. For those taking diltiazem ER for angina, it may take up to 2 weeks to feel less chest pain.

Question: What are some common side effects?

Plummer: A small percentage of people on diltiazem ER may experience swelling of the lower legs or hands. Other potential side effects are dizziness, weakness, nausea, diarrhea, flushing, congestion, constipation, cough or headache. If you’re older than age 65, you may be more sensitive to some of these side effects. You could also experience a hypotensive response, meaning your blood pressure may drop to a lower level quickly.

Question: Is there anything I can do to combat these side effects?

Plummer: Yes. Start with your diet: It’s good advice for anyone taking diltiazem ER to eat more fiber and stay well hydrated, which will help with constipation. You can also adjust when you’re taking the medication. If dizziness, lightheadedness or low blood pressure happen when you start diltiazem ER — or if you increase your dose — try taking the medication at bedtime instead of in the morning. To further decrease your chance of lightheadedness, always rise slowly when getting up from sitting or lying down. If you experience swelling in your legs, elevate them when sitting.

Question: When is swelling worrisome?

Plummer: To check for swelling, gently press your finger into the skin around your ankle. If the dimple you create holds, you should call your physician. For some, this reaction (called pitting edema) can be a sign of a more serious health problem, including heart failure, kidney disease or a blood clot.

Question: What about serious side effects?

Plummer: Serious side effects after taking diltiazem ER are pretty rare but may include:

  • Fainting
  • Severe abdominal pain
  • Dark urine
  • Persistent nausea or vomiting
  • Unusual dreams
  • Yellowing of the skin and eyes
  • Mood changes, including feeling depressed or agitated

Some may experience a change in heartbeat and/or new or worsening symptoms of heart failure, including shortness of breath, tiredness or sudden weight gain. Finally, in rare cases, acute liver injury may occur. The damage can be reversed upon stopping the medication.

Question: Are there any foods or beverages I should avoid while on diltiazem ER?

Plummer: Don’t drink grapefruit juice, because it may increase levels of diltiazem ER in your system, which could increase the drug’s effects and side effects. And since diltiazem ER can make people dizzy, especially seniors, you should avoid alcohol and marijuana to ensure that you don’t get even more dizzy. Speaking of marijuana, diltiazem ER also increases levels of THC and CBD in the body.

Question:  Are there any meds I should avoid while on diltiazem ER?

Plummer: Yes. Beta-blockers and certain statins, such as atorvastatin and simvastatin, are not recommended when you’re on diltiazem ER. Other medications that could cause problems include colchicine (for gout), rifampin (an antibiotic), carbamazepine (an anticonvulsant) and eletriptan (for migraines). This is not a complete list, so please consult your health care team for more details.

There are other common medications that may require dosage adjustments when used with diltiazem ER. These include many antivirals, herbs, some seizure medications, estrogen derivatives, oncology medications, some depression medications and some steroids. If you see different doctors, make sure that they all know you’re taking diltiazem ER — and check in with your pharmacist, too.

Taking your high blood pressure medication is the first step. Learn what else you can do to lower your risk of a stroke today.