Non-dihydropyridine calcium channel blockers are a class of drugs that reduce heart rate and blood pressure by affecting the electrical activity of the heart and the smooth muscle of blood vessels. Unlike dihydropyridines, which primarily target blood vessels, non-dihydropyridines have a more significant effect on the heart itself. This makes them useful for treating conditions where both heart rate and blood pressure need to be managed.
How do non-dihydropyridines work?
These drugs work by blocking L-type calcium channels in the heart muscle (myocardium) and the sinoatrial (SA) and atrioventricular (AV) nodes [1]. By reducing the influx of calcium into these cells, they slow down the rate at which the heart beats and decrease the force of its contractions. They also cause vasodilation, relaxing and widening blood vessels, which lowers blood pressure.
What conditions do non-dihydropyridines treat?
Non-dihydropyridine calcium channel blockers are primarily prescribed for:
* Supraventricular Tachycardia (SVT): They can help to slow down a rapid heart rate originating from the upper chambers of the heart [1].
* Atrial Fibrillation (AFib): They are used to control the ventricular rate (how fast the lower chambers of the heart beat) in patients with AFib [1].
* Hypertension (High Blood Pressure): They contribute to lowering blood pressure by reducing cardiac output and vasodilation [2].
* Angina Pectoris: By reducing the heart's workload and improving blood supply, they can alleviate chest pain associated with angina.
What are the main non-dihydropyridine drugs?
The two main non-dihydropyridine calcium channel blockers are verapamil and diltiazem [1][2]. Both are effective, but they may have slightly different profiles regarding their effects on the heart and blood vessels, and their potential side effects.
What are the potential side effects?
Common side effects of non-dihydropyridines include constipation, dizziness, headache, fatigue, and slow heart rate (bradycardia) [2]. Due to their effects on the heart's electrical system, they can also cause AV block, a condition where the electrical signal between the heart's upper and lower chambers is slowed or interrupted. These medications should be used with caution in patients with heart failure or certain pre-existing heart conditions.
How do non-dihydropyridines differ from dihydropyridines?
The key difference lies in their primary site of action. Dihydropyridines (like amlodipine or nifedipine) mainly target calcium channels in blood vessel walls, leading to significant vasodilation and blood pressure reduction. Non-dihydropyridines (verapamil and diltiazem) have a more pronounced effect on the heart muscle and its electrical conduction system, influencing both heart rate and contractility in addition to vasodilation [1][2]. This distinction influences their therapeutic uses and contraindications.
Are there drug interactions to be aware of?
Yes, non-dihydropyridines can interact with other medications. For instance, they can increase the levels and effects of certain statins and may interact with beta-blockers, increasing the risk of bradycardia and heart block. It is crucial for patients to inform their healthcare provider about all medications, including over-the-counter drugs and supplements, they are taking.