Medically reviewed by Jessica Swirble, PharmD
Last updated on 7/3/2024

Drug Information | Side Effects | Use & Dosage | Request a Prescription

The use of diltiazem ER can lead to various side effects in some individuals.

Common mild side effects of diltiazem ER use include:

• Dizziness
  
• Fatigue
  
• Headache
  
• Nausea
  
• Diarrhea
  
• Constipation
  
• Flushing
  
• Rash
  
• Swelling of the hands, feet, ankles, or lower legs
  
  

More severe side effects of diltiazem ER use can include:

• Signs of an allergic reaction (like rash, hives, swelling, difficulty breathing or swallowing)
  
• Slow or irregular heartbeats
  
• Fainting
  
• Low blood pressure
  
• Severe dizziness
  
• Shortness of breath
  
• Severe tiredness
  
• Unusual weight gain
  
• Yellowing of skin or eyes (jaundice)
  
• Severe stomach or abdominal pain
  
• Persistent nausea or vomiting
  
  

If you experience any severe or concerning side effects while taking diltiazem ER, contact your healthcare provider right away.

Inform your healthcare provider about any existing medical conditions, allergies, or other medications you are taking before starting treatment with diltiazem ER. This includes prescription drugs, over-the-counter medications, and dietary supplements, as they may interact with diltiazem ER.

Tell your provider if you are taking these medications or supplements:

• Beta-blockers
  
• Digoxin
  
• Amiodarone
  
• Clonidine
  
• Carbamazepine
  
• Cyclosporine
  
• Rifampin
  
• Cimetidine
  
• Colchicine
  
• St. John’s Wort
  
• Antibiotics
  
• Antifungals
  
• Antianxiety medications
  
• Anti-nausea medications
  
• Blood pressure medications
  
• Anti-seizure medications
  
• Antidepressants
  
• Statins
  
  

You should also mention medical conditions such as:

• Heart disease or heart failure
  
• Wolff-Parkinson-White syndrome
  
• Lown-Ganong-Levine syndrome
  
• Low blood pressure
  
• Liver disease
  
• Kidney disease
  
• Certain types of irregular heartbeats
  
  

If you are pregnant, planning to become pregnant, or breastfeeding, discuss the potential risks and benefits of using diltiazem ER with your healthcare provider.

Take diltiazem ER exactly as prescribed by your healthcare provider. Do not exceed the recommended dose or duration of treatment.

Your provider may direct you to avoid alcohol while taking diltiazem ER, as it can increase the risk of side effects.

Your provider may direct you to avoid grapefruit juice while taking diltiazem ER, as it can increase the risk of side effects.

Diltiazem ER can cause dizziness. Avoid driving or operating heavy machinery until you know how the medication affects you.

Complete the full course of treatment, even if you feel better, to ensure the medication's effectiveness in managing your condition.

In case of a diltiazem ER overdose, seek medical attention immediately. Symptoms of overdose may include severe dizziness, fainting, difficulty breathing, or an unusually slow or irregular heartbeat. If you suspect an overdose, contact the poison control helpline at 1-800-222-1222 or call emergency services.