Drug Information: Diltiazem
Detailed information regarding Diltiazem, a medication commonly used in clinical settings. Diltiazem is a calcium channel blocker primarily used to treat hypertension, angina, and certain heart rhythm disorders such as atrial fibrillation and atrial flutter. It works by relaxing blood vessels, which lowers blood pressure, and by slowing down the heart rate. This makes it a versatile medication for managing cardiovascular conditions.
Category
Antiarrhythmic
Mechanism of Action
Diltiazem is a calcium channel blocker, specifically a benzothiazepine derivative. It exerts its therapeutic effects by selectively blocking the influx of calcium ions into cardiac and vascular smooth muscle cells. This blockade primarily occurs via the L-type calcium channels, which are responsible for mediating calcium entry during cellular depolarization.
Specifically, Diltiazem’s mechanism of action involves the following steps:
1. **Calcium Channel Blockade:** Diltiazem binds to L-type calcium channels in the heart and blood vessels, preventing calcium ions from entering the cells.
2. **Vasodilation:** By reducing calcium influx into vascular smooth muscle cells, Diltiazem causes relaxation and vasodilation of both coronary and peripheral arteries. This leads to a decrease in systemic vascular resistance and a reduction in blood pressure.
3. **Cardiac Effects:** In the heart, Diltiazem primarily affects the sinoatrial (SA) and atrioventricular (AV) nodes. By blocking calcium channels in these areas, it slows down the heart rate and prolongs AV nodal conduction. This can help control certain types of arrhythmias, such as atrial fibrillation and supraventricular tachycardia. Diltiazem also has a negative inotropic effect, meaning it reduces the force of heart muscle contraction, but this effect is less pronounced compared to other calcium channel blockers like verapamil.
4. **Reduction of Myocardial Oxygen Demand:** Diltiazem reduces myocardial oxygen demand by decreasing afterload (due to vasodilation) and heart rate. This is beneficial in treating angina, as it helps to alleviate chest pain caused by insufficient blood supply to the heart muscle.
Clinical Uses
Diltiazem is used for a variety of cardiovascular conditions:
* **Atrial Fibrillation and Flutter:** Diltiazem helps control heart rate in patients with atrial fibrillation and atrial flutter. It slows down the AV nodal conduction, reducing the number of atrial impulses that reach the ventricles.
* **Hypertension:** Diltiazem is effective in lowering blood pressure by relaxing blood vessels. It can be used as a monotherapy or in combination with other antihypertensive agents.
* **Angina Pectoris:** Diltiazem is used to treat both stable and variant (Prinzmetal’s) angina. It reduces myocardial oxygen demand by decreasing heart rate and blood pressure, and it can also prevent coronary artery spasm.
* **Supraventricular Tachycardia (SVT):** Diltiazem can be used to terminate or prevent SVT episodes by slowing down AV nodal conduction.
* **Vasospastic Disorders:** Diltiazem can be helpful in treating conditions caused by vasospasm such as Raynaud’s phenomenon.
Dosage
**Adult Dosage:**
* **Oral:** The typical starting dose is 30 mg four times daily, or 60 mg three times daily. The dosage can be increased gradually, usually at 1- to 2-day intervals, to a maximum of 360 mg per day in divided doses. Sustained-release formulations are also available, allowing for once- or twice-daily dosing. The initial dose of extended-release diltiazem is typically 120 to 180 mg once daily, which may be increased gradually.
* **Intravenous (IV):** For rapid heart rate control in atrial fibrillation or SVT, the initial bolus dose is 0.25 mg/kg IV over 2 minutes. If needed, a second bolus of 0.35 mg/kg IV over 2 minutes can be given after 15 minutes. Following the bolus, a continuous IV infusion of 5-15 mg/hour can be used to maintain heart rate control.
**Pediatric Dosage:**
* Use in pediatric patients is generally limited and should be under the direction of a specialist. IV diltiazem has been used in children with supraventricular tachycardia. Dosing guidelines must be consulted.
**Important Considerations:** Dosage adjustments are often necessary based on individual patient factors, such as age, renal function, liver function, and concurrent medications. Elderly patients may require lower starting doses.
Indications
* Hypertension (high blood pressure)
* Angina pectoris (chest pain)
* Atrial fibrillation and atrial flutter (irregular heart rhythms)
* Supraventricular tachycardia (SVT)
* Vasospastic angina (Prinzmetal’s angina)
Contraindications
* Hypersensitivity to diltiazem or any of its components
* Sick sinus syndrome (unless a functioning pacemaker is present)
* Second- or third-degree AV block (unless a functioning pacemaker is present)
* Hypotension (systolic blood pressure less than 90 mmHg)
* Acute myocardial infarction with pulmonary congestion
* Atrial fibrillation or flutter associated with Wolff-Parkinson-White syndrome
* Concurrent use with intravenous beta-blockers
FAQ
**Q: What is Diltiazem used for?**
A: Diltiazem is primarily used to treat high blood pressure (hypertension), chest pain (angina), and certain heart rhythm disorders like atrial fibrillation and supraventricular tachycardia.
**Q: How does Diltiazem work?**
A: Diltiazem is a calcium channel blocker. It works by relaxing blood vessels and slowing down heart rate, making it easier for the heart to pump blood and reducing blood pressure.
**Q: What are the common side effects of Diltiazem?**
A: Common side effects include headache, dizziness, fatigue, constipation, and edema (swelling) in the ankles and feet.
**Q: Can I take Diltiazem if I have low blood pressure?**
A: No, Diltiazem is contraindicated in patients with hypotension (low blood pressure) as it can further lower blood pressure.
**Q: Can I drink alcohol while taking Diltiazem?**
A: Alcohol should be avoided or used with caution while taking Diltiazem, as it can increase the risk of dizziness and lightheadedness.
**Q: What should I do if I miss a dose of Diltiazem?**
A: If you miss a dose, take it as soon as you remember. However, if it’s almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not double the dose to catch up.
**Q: Does Diltiazem interact with other medications?**
A: Yes, Diltiazem can interact with several medications, including beta-blockers, digoxin, cimetidine, and certain statins. It’s essential to inform your doctor about all the medications you are taking.
**Q: How long does it take for Diltiazem to start working?**
A: The onset of action varies depending on the condition being treated. For hypertension, it may take several days to weeks to see the full effect. For angina and heart rhythm disorders, the effects may be noticeable within hours or days.
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