The Enduring Role of Verapamil in Modern Medicine
First approved for medical use in the U.S. in 1981, verapamil is a well-established medication that continues to hold its place in the therapeutic arsenal [1.2.5]. As a non-dihydropyridine calcium channel blocker (CCB), its primary mechanism involves inhibiting the influx of calcium ions into the cells of the heart and blood vessels [1.5.4]. This action results in the relaxation of blood vessels, which lowers blood pressure, and an increase in the supply of blood and oxygen to the heart, all while reducing the heart's workload [1.2.3]. It also slows electrical activity in the heart, making it effective for controlling certain arrhythmias [1.5.3].
FDA-Approved and Off-Label Indications
Verapamil is available by prescription only and is officially approved by the FDA for several cardiovascular conditions [1.2.3, 1.3.2]:
- Hypertension (High Blood Pressure): It is used, often as an add-on therapy, to relax blood vessels so the heart doesn't have to pump as hard [1.3.1, 1.3.2].
- Angina (Chest Pain): It is effective for chronic stable angina, unstable angina, and vasospastic (Prinzmetal's) angina [1.3.2].
- Cardiac Arrhythmias: The immediate-release tablets are used to treat and prevent irregular heartbeats, specifically supraventricular tachycardias (SVT) and to control ventricular rate in atrial fibrillation or atrial flutter [1.3.1, 1.3.2].
Beyond these core uses, verapamil is sometimes prescribed "off-label" for other conditions, most notably for the prevention of migraine and cluster headaches [1.2.4]. While not officially approved by the FDA for this purpose, clinicians may use it when other treatments have failed [1.2.4].
Understanding the Side Effects and Risks
Like all medications, verapamil carries a risk of side effects. The most common one is constipation, which is reported in about 7% of patients [1.6.4]. Other frequent side effects include dizziness, headache, and nausea [1.6.1, 1.6.4].
Serious Adverse Events and Contraindications
Clinicians must exercise caution, as more serious side effects can occur. These include:
- Heart Failure: Verapamil has a negative inotropic effect (weakens heart muscle contraction) and should be avoided in patients with severe left ventricular dysfunction or moderate to severe heart failure [1.7.2].
- Hypotension (Low Blood Pressure): The medication can sometimes lower blood pressure too much, leading to dizziness or fainting [1.7.2]. It is contraindicated in patients with a systolic pressure below 90 mm Hg [1.7.4].
- Bradycardia (Slow Heartbeat) and AV Block: By slowing electrical conduction in the heart, verapamil can cause an excessively slow heart rate or heart block. It is contraindicated in patients with sick sinus syndrome or second- or third-degree AV block, unless they have a functioning pacemaker [1.7.1, 1.7.4].
- Liver Injury: Elevations in liver enzymes have been reported, so periodic monitoring of liver function is prudent [1.7.2]. Symptoms like upper right stomach pain, yellowing skin, or extreme tiredness require immediate medical attention [1.6.1].
- Drug Interactions: Verapamil interacts with many other drugs. It can increase the effects of alcohol and should not be taken with grapefruit juice, which can increase the drug's concentration in the blood [1.3.1, 1.8.4]. It also has significant interactions with beta-blockers, certain statins (like simvastatin and lovastatin), digoxin, and many others [1.7.3, 1.7.4].
Verapamil in Comparison to Other Calcium Channel Blockers
Verapamil belongs to the non-dihydropyridine class of CCBs, along with diltiazem. This class is distinct from the dihydropyridine CCBs, like amlodipine and nifedipine. The primary difference is that non-dihydropyridines have a more significant effect on heart rate and contractility, whereas dihydropyridines act more strongly on peripheral blood vessels [1.4.1, 1.8.4].
| Feature | Verapamil | Diltiazem | Amlodipine (A Dihydropyridine) |
|---|---|---|---|
| Primary Site of Action | Heart and blood vessels [1.4.1] | Heart and blood vessels [1.4.1] | Primarily blood vessels [1.4.1, 1.8.5] |
| Effect on Heart Rate | Decreases [1.4.1] | Decreases [1.4.1] | May cause reflex increase [1.4.1] |
| Main Clinical Uses | Arrhythmias, Angina, Hypertension [1.3.2] | Rate control in AFib, Angina, Hypertension [1.9.4] | Hypertension, Angina [1.8.5] |
| Common Side Effect Profile | Constipation, headache, dizziness [1.6.4] | Edema (swelling), headache, dizziness [1.9.4] | Edema (swelling), flushing, palpitations [1.8.4] |
Because of its more potent effect on slowing the heart rate, verapamil is often preferred for treating atrial arrhythmias compared to diltiazem [1.4.4]. However, dihydropyridines like amlodipine may produce a greater reduction in systemic vascular resistance [1.4.1].
Alternatives and Future Outlook
For hypertension, numerous alternatives exist across different drug classes, including ACE inhibitors (e.g., lisinopril), ARBs (e.g., losartan), beta-blockers (e.g., metoprolol), and diuretics [1.8.5]. For atrial fibrillation rate control, beta-blockers are often considered the most effective first-line drug class, with non-dihydropyridine CCBs like verapamil and diltiazem serving as a primary alternative, especially for patients with conditions like COPD [1.9.3].
Conclusion
So, is verapamil still prescribed? The answer is a definitive yes. Despite being on the market for over four decades and the availability of newer agents, verapamil remains a valuable and frequently prescribed medication for its specific indications in managing hypertension, angina, and particularly cardiac arrhythmias [1.2.1, 1.2.5]. Its unique mechanism of action as a non-dihydropyridine CCB secures its place in clinical guidelines, especially for patients who require heart rate control. However, its use requires careful patient selection and monitoring due to a significant potential for drug interactions and a clear list of contraindications. Its continued prescription underscores its proven efficacy when used appropriately in the right patient population.
For more information from an authoritative source, you can visit: Verapamil: MedlinePlus Drug Information [1.3.1]
