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Cardizem CD

Diltiazem ER 

Diltiazem ER is an FDA-approved calcium channel blocker used primarily for treating hypertension and angina. It works by relaxing blood vessels and increasing blood flow, thus easing the heart’s workload and enhancing its oxygen supply. Available in various forms, including extended-release capsules and tablets, as well as injectable solutions, Diltiazem ER should be taken exactly as prescribed, typically once daily. Common side effects include dizziness, swelling, and headaches, with more severe risks involving heart complications or liver issues. It is crucial not to crush or chew the capsules and to store the medication properly at room temperature, away from light and moisture. Patients must consult their healthcare provider for any potential drug interactions and adhere strictly to dosing instructions to avoid adverse effects.

Product Overview

Diltiazem ER is a calcium channel blocker widely used to treat hypertension (high blood pressure) and angina (chest pain). Approved by the FDA, this medication aids in preventing strokes, heart attacks, and kidney problems by relaxing the blood vessels so the heart does not have to pump as hard. It also increases the supply of blood and oxygen to the heart while reducing its workload. By blocking calcium transport into the heart and arterial cells, Diltiazem ER decreases impulses and stabilizes the heart rate, making it effective for managing blood pressure and heart rhythm disorders.

Diltiazem ER is available in various strengths and forms, including extended-release capsules and tablets ranging from 120mg to 420mg, injectable solutions at 5mg/mL, and powder for injection at 100mg. Tablets are also available in lower doses, from 30 to 120mg. Patients are advised to take the medication exactly as prescribed, typically once daily for extended-release forms to maintain steady blood levels. It can be taken with or without food but should be taken consistently in the same manner.

Common side effects of Diltiazem ER include dizziness, headaches, swelling, and fatigue, while more serious effects may involve severe allergic reactions, liver problems, or heart complications. Patients must follow their healthcare provider’s instructions regarding missed doses and storage, ensuring the medication is kept away from light and moisture at room temperature. Interactions with other medications like beta-blockers or digoxin can enhance side effects, thus requiring careful management by a healthcare provider. Patients should never crush or chew extended-release capsules, and sudden discontinuation should be avoided without medical advice, as it may worsen symptoms or trigger withdrawal effects.

Uses of Diltiazem ER

  • Hypertension
  • Angina
  • Elevated blood pressure and cardiac discomfort

How to Use Diltiazem ER?


Diltiazem ER comes in multiple dosage forms and strengths for easier administration. Here is a list of them:

  • Extended-release capsules/tablets:
    • 120mg
    • 180mg
    • 240mg
    • 300mg
    • 360mg
    • 420mg
  • Injectable solution:
    • 5mg/mL
  • Powder for injection:
    • 100mg
  • Tablets:
    • 30mg
    • 60mg
    • 90mg
    • 120mg

Recommended Dosage for Different Patients

Angina (Chest Pain):

  • Start with 30 mg four times daily. Adjust dose every 1-2 days until control is achieved. Typical maintenance is 180-360 mg per day, divided into 3-4 doses. Maximum of 360 mg/day.
  • Extended Release (Various Brands): Start with 120-180 mg once daily. Adjust over 7-14 days based on response. Maintenance usually ranges from 120-320 mg/day. Max varies from 360 mg/day to 540 mg/day, depending on the brand.

Hypertension (High Blood Pressure):

  • Extended Release (Various Brands): Start with 180-240 mg once daily. Adjust the dose after 14 days. Maintenance is typically 180-420 mg/day, with a maximum of 480-540 mg/day, depending on the brand.

Extended-Release Twice-Daily Dosing:

  • Start with 60-120 mg every 12 hours. You may adjust after 14 days. Maintenance is usually 240-360 mg/day.

Paroxysmal Supraventricular Tachycardia (Rapid Heart Rate):

  • Initial IV Dose: 0.25 mg/kg (average adult dose is 20 mg) given over 2 minutes. If the response is inadequate, a second dose of 0.35 mg/kg may be given after 15 minutes. Some doctors may repeat doses every 15 minutes.
  • Continuous IV Infusion: Start with 10 mg/hour, up to a maximum of 15 mg/hour for up to 24 hours.

Atrial Fibrillation/Flutter (Heart Rhythm Problems):

  • Same as dosing for Paroxysmal Supraventricular Tachycardia.

[Note: Remember, these recommendations may vary from person to person. Discuss it with your doctor, and they’ll customize your dosage accordingly.]

How to Take It?

  • Take Diltiazem ER as your healthcare provider prescribes, typically once daily. It’s best to take it at the same time each day to maintain consistent blood levels of the medication.
  • You can take Diltiazem ER with or without food, but it’s a good idea to take it the same way each time. Some people find that taking it with food helps to reduce stomach upset.
  • Do not chew, crush, or break the extended-release capsules or tablets. They must be swallowed whole to ensure the medication is released slowly over time and to prevent a spike in the concentration of the drug in your bloodstream, which could increase side effects.
  • Follow your doctor’s instructions carefully regarding dosage. If you have difficulty swallowing pills, ask your doctor about using a different form of diltiazem that might be easier to take.
  • Keep regular appointments with your healthcare provider to adjust the dose if necessary and to check for side effects, especially if you are starting the medication, changing the dose, or have recently stopped taking it.

[Note: Your doctor will decide the right amount for you based on your condition, following guidelines and studies on the drug. They’ll adjust it as needed over time.]

How Does Diltiazem ER Work?

Diltiazem ER (extended-release) works by blocking calcium channels in the heart and blood vessels. This action helps to relax the muscles of the heart and blood vessels, which lowers blood pressure and reduces the heart’s workload. Diltiazem ER is particularly effective in controlling the heart rate, especially in conditions like hypertension (high blood pressure) and certain types of abnormal heart rhythms, including atrial fibrillation. By slowing the influx of calcium ions during the cardiac muscle contraction cycle, diltiazem decreases the force of contraction (negative inotropy). It prolongs the time to the next contraction, which can help to stabilize the heart rhythm and reduce chest pain in conditions like angina.

Important Safety Information

Side Effects

Common side effects of this medication may include:

  • Swelling
  • Infections or flu-like symptoms
  • Difficulty breathing
  • Headaches, dizziness, or weakness
  • Reduced heart rate
  • Pain, bruising, swelling, or irritation at the injection site
  • Nausea or upset stomach
  • Skin rash

Serious side effects of this medication may include:

  • Hives
  • Difficulty breathing
  • Swelling of the face, lips, tongue, or throat
  • Fever and sore throat
  • Burning eyes
  • Skin pain accompanied by a red or purple rash that blisters and peels
  • Chest pain
  • Slow or pounding heartbeats
  • Fluttering sensation in the chest
  • Lightheadedness
  • Swelling in the extremities
  • Rapid weight gain
  • Shortness of breath

[Note: Remember, this list may not cover all possible side effects. Always consult with your healthcare giver for medical advice about side effects.]


  • Slow Heart Rate or Heart Block: Diltiazem ER may reduce your heart rate, potentially leading to weakness or fainting, particularly if you take digoxin or beta-blockers or have conditions affecting your heart rhythm. Before starting Diltiazem ER, discuss your full medical history with your provider to ensure it’s safe.
  • Worsening Heart Failure: This medication can exacerbate heart failure symptoms, such as chest pain, breathlessness, fatigue, swelling of legs and feet, or bloating, especially in patients with pre-existing heart conditions. Notify your provider if you experience any worsening symptoms.
  • Severely Low Blood Pressure: Diltiazem ER can significantly lower your blood pressure, causing symptoms like dizziness or fatigue. This effect can be more pronounced when starting the medication or increasing the dose. Sit or lie down slowly if you feel dizzy, and contact your provider if the symptoms persist. Seek immediate medical attention if you experience a fall.
  • Liver Issues: Diltiazem ER can increase liver enzymes, potentially leading to liver damage. Your provider may perform liver function tests before and during treatment. Watch for symptoms such as severe nausea, right-sided stomach pain, fatigue, or jaundice, and seek medical help if they occur.
  • Severe Skin Reactions (Extended-Release Tablets): On rare occasions, Diltiazem ER can cause life-threatening skin reactions like Stevens-Johnson syndrome or toxic epidermal necrolysis. Stop taking the medication and seek emergency medical care if you develop a rash, fever, blisters, facial swelling, or breathing difficulties.


  • Allergies: Inform your doctor or pharmacist if you are allergic to diltiazem or have other allergies. Inactive ingredients in the product may trigger allergic reactions.
  • Medical History: Discuss your medical history with your healthcare provider, particularly if you have heart rhythm problems (like sick sinus syndrome or atrioventricular block), liver disease, kidney disease, or heart failure.
  • Dizziness Risk: Diltiazem may cause dizziness. Avoid alcohol and marijuana as they can exacerbate this effect. Do not drive or operate machinery until you know how this medication affects you.
  • Alcohol and Marijuana Use: Limit alcohol and discuss any marijuana use with your doctor, as both can increase dizziness.
  • Surgery Precautions: Before surgery, inform your doctor or dentist of all products you use, including all medications.
  • Sensitivity in Older Adults: Older adults may be more susceptible to side effects, particularly dizziness, constipation, and swelling of ankles or feet.
  • Use During Pregnancy: Use diltiazem during pregnancy only if clearly needed. Discuss all risks and benefits with your doctor.
  • Breastfeeding: Diltiazem passes into breast milk and could affect a nursing infant. Consult your doctor before breastfeeding.


  • Sick Sinus Syndrome: Do not use it unless a functioning ventricular pacemaker is installed.
  • AV Block: Contraindicated in a second or third-degree atrioventricular block unless a functioning ventricular pacemaker is present.
  • Hypotension: Not recommended for use if systolic blood pressure is less than 90 mm Hg.
  • Hypersensitivity: Should not be used by individuals who have an allergy to diltiazem.
  • Acute Conditions: Avoid use during acute myocardial infarction and pulmonary complications.

Missed Dose

If you miss a dose of Diltiazem ER, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up. It’s important to take the medication consistently as prescribed to maintain its effectiveness, particularly in managing blood pressure and heart conditions. If you frequently miss doses, setting reminders or discussing the issue with your healthcare provider might be helpful to ensure proper treatment adherence.

[Note: If you have missed a medication dose and are unsure when to take the next one, immediately consult your doctor or pharmacist.]


An overdose of Diltiazem ER can lead to severe and potentially life-threatening complications. Symptoms may include profound dizziness, confusion, slowed heart rate, fainting, and difficulty breathing. In extreme cases, an overdose can result in coma or significant cardiac issues such as heart block or dangerously low blood pressure. If you suspect an overdose of Diltiazem ER, it is critical to seek emergency medical attention immediately to address these risks and prevent further health deterioration. Prompt medical intervention can mitigate the adverse effects and provide necessary supportive care.

[Note: If you consumed more than the recommended dose, get medical help immediately or call the Poison Help line at 1-800-222-1222.]


  • Store the medication in a sealed container at room temperature, away from heat, moisture, and direct sunlight.
  • Ensure the medication does not freeze.
  • Keep the medication out of reach of children.
  • Dispose of any expired or no longer-needed medication.
  • Consult your healthcare provider for proper disposal methods for unused medicine.

[Note: Discuss with your healthcare professional about the proper disposal of any unused medicine and any questions you may have regarding its storage.]

Diltiazem ER Interactions

  • Beta-blockers (e.g., metoprolol, atenolol) Can increase the risk of heart problems, such as slowed heart rate and low blood pressure.
  • Digoxin: Diltiazem increases the levels of digoxin in the blood, which could lead to toxicity.
  • Statins (e.g., simvastatin, atorvastatin): Diltiazem can raise the levels of these cholesterol-lowering drugs, increasing the risk of side effects such as muscle pain.
  • Cyclosporine: Diltiazem can increase cyclosporine levels in the blood, potentially leading to kidney damage or other side effects.
  • Benzodiazepines (e.g., midazolam, triazolam): Diltiazem can increase the effects of these sedatives, leading to enhanced drowsiness and decreased motor skills.
  • Cimetidine: This medication can increase diltiazem levels in the blood, heightening its effects and side effects.
  • Rifampin: This antibiotic can decrease the effectiveness of diltiazem by increasing its metabolism in the liver.
  • Grapefruit Juice: This can increase the levels of diltiazem in the blood, potentially leading to increased side effects.
  • Antiarrhythmic drugs (e.g., amiodarone): Can increase the risk of irregular heartbeats when taken with diltiazem.
  • Blood pressure medications: Can enhance the blood pressure-lowering effects of diltiazem, possibly leading to hypotension.

[Note: This isn’t a complete list, and there could be other drugs that interact with Diltiazem ER. Make sure to tell your doctor about any prescription, over-the-counter medicines, and herbal products you’re taking.]

Diltiazem ER Alternatives

[Note: Your doctor will choose what’s best for you. Don’t use any of these alternative medications without consulting your healthcare provider. Taking them by yourself may cause serious side effects.] 

Frequently Asked Questions

Can you open diltiazem ER capsules?

The ability to open diltiazem ER capsules varies by brand. Brands such as Tiazac and Taztia XT allow the contents to be sprinkled onto a spoonful of applesauce. However, other brands and generics, like Cardizem CD, must be swallowed whole. If you have difficulty swallowing pills, consult your healthcare provider or pharmacist to determine which form of the medication is suitable for you.

How quickly does diltiazem ER start working?

Diltiazem ER takes effect a few hours after administration, but the full benefits may not be noticeable until 2 to 4 weeks of consistent use. If your blood pressure or chest pain remains uncontrolled after this period, your healthcare provider may adjust your dosage. Following a dosage change, observing the complete effects could take an additional two weeks. To monitor the effectiveness of diltiazem ER, regularly measure your blood pressure at home or record any chest pain episodes. Sharing this information with your provider during appointments can help optimize your treatment plan.

Is it safe to drink alcohol while taking diltiazem ER?

It is advisable to avoid alcohol while on diltiazem ER, as it can increase the likelihood of experiencing side effects such as dizziness or falls. Additionally, alcohol can interfere with the medication’s effectiveness in managing your blood pressure. If completely abstaining from alcohol is challenging, discuss with your healthcare provider to determine a safe amount of alcohol consumption during your treatment.

Is it safe to crush diltiazem ER tablets?

Crushing diltiazem ER tablets is not recommended. The extended-release formulation has a special coating designed to gradually release the drug into your system. Crushing the tablet disrupts this coating, potentially decreasing the medication’s effectiveness or increasing the risk of side effects. If you have difficulty swallowing diltiazem ER, consult your healthcare provider about alternative options.

Is diltiazem ER considered a beta blocker?

Diltiazem ER is not a beta blocker; it is classified as a calcium channel blocker. Both calcium channels and beta blockers manage high blood pressure and chest pain, but they function differently. Due to potential heart-related side effects, it is generally uncommon for diltiazem ER to be prescribed alongside beta blockers.

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