Diltiazem

1. Introduction

Diltiazem is a calcium channel blocker (CCB) used to treat hypertension, angina, and certain arrhythmias. It works by inhibiting calcium ion influx in cardiac and vascular smooth muscle, resulting in vasodilation, reduced heart rate, and decreased myocardial contractility. These effects lower blood pressure and improve oxygen delivery to the heart.

2. Indications

  • Approved Indications:
    • Hypertension (alone or in combination with other antihypertensive agents).
    • Stable angina (chronic) and vasospastic angina (Prinzmetal’s angina).
    • Rate control in atrial fibrillation or atrial flutter.
    • Supraventricular tachycardia (SVT).
  • Off-Label Uses:
    • Hypertrophic cardiomyopathy (to improve diastolic function).

3. Dosage

  • Hypertension:
    • Extended-release (ER): 180–240 mg once daily. Adjust as needed (maximum: 540 mg/day).
  • Angina:
    • Immediate-release: 30 mg 3–4 times daily.
    • Extended-release: 180–360 mg once daily.
  • Atrial Fibrillation/Supraventricular Tachycardia:
    • IV bolus: 0.25 mg/kg over 2 minutes, followed by 0.35 mg/kg if needed.
    • Continuous infusion: 5–15 mg/hour, adjusted based on response.

4. Administration

  • Oral: Swallow tablets or capsules whole; do not crush or chew extended-release formulations.
  • IV: Administer slowly over 2 minutes under ECG monitoring.
  • Food: Can be taken with or without food; however, consistent timing is recommended for extended-release forms.

5. Forms Available

  • Tablets (immediate-release): 30 mg, 60 mg, 90 mg, 120 mg.
  • Extended-release capsules: 120 mg, 180 mg, 240 mg, 300 mg, 360 mg.
  • Injectable solution: 5 mg/mL.

6. Side Effects

6.1. Common Side Effects

  • Headache.
  • Dizziness.
  • Fatigue.
  • Peripheral oedema.
  • Bradycardia.

6.2. Less Common Side Effects

  • Nausea.
  • Flushing.
  • Constipation.

6.3. Rare but Serious Side Effects

  • Heart block (AV block).
  • Severe hypotension.
  • Hepatotoxicity (elevated liver enzymes, rare liver failure).

7. Warnings

  • Heart Block and Bradycardia: Avoid use in patients with second- or third-degree AV block or sick sinus syndrome unless a pacemaker is in place.
  • Hypotension: Monitor closely in patients at risk of severe hypotension.
  • Congestive Heart Failure: Use cautiously, especially in patients with reduced left ventricular function.

8. Precautions

  • Use with caution in patients with hepatic or renal impairment, as metabolism and clearance may be reduced.
  • Monitor closely in elderly patients, who are more sensitive to the drug’s effects.
  • Avoid abrupt withdrawal, as this can worsen angina.

9. Interactions

  • Drug-Drug Interactions:
    • Beta-blockers: Increased risk of bradycardia and AV block.
    • Digoxin: May increase digoxin levels, requiring monitoring.
    • CYP3A4 inhibitors (e.g., azole antifungals, grapefruit juice): May increase diltiazem levels.
    • CYP3A4 inducers (e.g., rifampin): May reduce diltiazem levels.
  • Drug-Food Interactions:
    • Grapefruit juice may increase diltiazem levels, enhancing its effects.

10. Monitoring Parameters

  • Blood pressure and heart rate.
  • ECG (in patients with arrhythmias or IV administration).
  • Liver function tests in long-term therapy.
  • Signs of worsening heart failure, such as weight gain or dyspnoea.

11. Use in Children

  • Not commonly used in children; safety and efficacy in paediatric patients have not been well established.

12. Use in Pregnancy

  • Category C: Use only if benefits outweigh risks. Limited data suggests potential harm to the foetus.

13. Use in Elderly

  • Start with the lowest effective dose due to increased sensitivity to hypotension and bradycardia.

14. Use in Kidney Disease

  • Use cautiously, as diltiazem is excreted renally. Adjust dose or monitor for side effects in severe impairment.

15. Use in Liver Disease

  • Use cautiously, as diltiazem is extensively metabolised by the liver. Monitor liver function and consider dose reduction in severe hepatic impairment.

16. Patient Counselling Points

  • Take diltiazem as prescribed; do not skip doses or stop abruptly without consulting your doctor.
  • Report symptoms such as dizziness, fainting, or irregular heartbeats immediately.
  • Avoid grapefruit juice while on this medication.
  • Inform healthcare providers of diltiazem use before undergoing surgery or dental procedures.
  • For extended-release forms, take at the same time each day for consistent blood levels.

17. Table of Brand Names, Manufacturers, and Prices

Brand NameManufacturerPrice (USD)
CardizemBausch Health$25–50 (30 tablets, 180 mg ER)
TiazacAllergan$30–60 (30 tablets, 240 mg ER)
Generic DiltiazemVarious$15–30 (30 tablets, 180 mg ER)

18. FAQs (15 Questions)

  1. What is diltiazem used for?
    Diltiazem is used to treat hypertension, angina, and certain arrhythmias like atrial fibrillation.
  2. How does diltiazem work?
    It blocks calcium channels, relaxing blood vessels and slowing the heart rate.
  3. Can diltiazem cause side effects?
    Yes, common side effects include dizziness, headache, and swelling in the ankles or feet.
  4. How should diltiazem be taken?
    Swallow tablets or capsules whole, preferably at the same time each day.
  5. Can diltiazem interact with other medications?
    Yes, it interacts with beta-blockers, digoxin, and CYP3A4 inhibitors like grapefruit juice.
  6. Can diltiazem cause low blood pressure?
    Yes, it may cause hypotension, especially at higher doses or in sensitive patients.
  7. Is diltiazem safe in pregnancy?
    It is not typically recommended unless the benefits outweigh the risks.
  8. Can diltiazem be stopped suddenly?
    No, stopping abruptly may worsen angina or lead to rebound hypertension.
  9. What should I do if I miss a dose of diltiazem?
    Take it as soon as you remember, but skip it if it’s close to the next dose.
  10. Can elderly patients use diltiazem?
    Yes, but they should start at lower doses due to increased sensitivity.
  11. Does diltiazem require monitoring?
    Yes, blood pressure, heart rate, and ECG should be monitored, especially during dose adjustments.
  12. Can I drink alcohol while taking diltiazem?
    Alcohol may increase the risk of dizziness or hypotension and should be avoided or limited.
  13. Does diltiazem affect kidney function?
    It is primarily metabolised by the liver but should be used cautiously in patients with severe kidney impairment.
  14. Can diltiazem cause swelling?
    Yes, peripheral oedema (swelling in the legs or ankles) is a common side effect.
  15. How should diltiazem be stored?
    Store at room temperature, away from light and moisture.