From the Guidelines
Calcium channel blockers lower blood pressure by preventing calcium from entering the muscle cells of the heart and blood vessels, thereby relaxing and widening blood vessels and reducing resistance to blood flow. This mechanism of action is supported by the American Heart Association Council for High Blood Pressure Research, which states that calcium ions play a crucial role in vascular smooth muscle cell contraction and cardiac function 1. The dihydropyridine calcium channel blockers, such as amlodipine and nifedipine, are highly selective for arterial/arteriolar tissues and cause vasodilation, whereas the nondihydropyridine calcium channel blockers, such as verapamil and diltiazem, have negative chronotropic and dromotropic effects on the heart 1.
The benefits of calcium channel blockers in lowering blood pressure and reducing cardiovascular risk have been demonstrated in several studies. For example, the INVEST study found that verapamil and atenolol had similar effects on cardiovascular outcomes in patients with hypertension and coronary heart disease 1. Similarly, the ALLHAT study found that chlorthalidone, lisinopril, and amlodipine had similar effects on cardiovascular outcomes in patients with hypertension 1. The European Society of Hypertension and the European Society of Cardiology also recommend the use of calcium channel blockers in patients with hypertension and coronary heart disease, as they have been shown to reduce the incidence of cardiovascular events and improve outcomes 1.
Some key points to consider when using calcium channel blockers include:
- Typical starting doses are amlodipine 2.5-5 mg daily, nifedipine extended-release 30 mg daily, diltiazem extended-release 120-180 mg daily, and verapamil extended-release 120-180 mg daily
- Side effects may include headache, dizziness, flushing, ankle swelling, constipation, and gum overgrowth
- Calcium channel blockers are particularly effective for older adults, African Americans, and people with certain conditions like angina or Raynaud's phenomenon
- They can be taken with or without food, but grapefruit juice should be avoided as it can increase drug levels in the bloodstream
Overall, calcium channel blockers are a effective and safe treatment option for lowering blood pressure and reducing cardiovascular risk, and should be considered as part of a comprehensive treatment plan for patients with hypertension and coronary heart disease 1.
From the FDA Drug Label
Amlodipine is a peripheral arterial vasodilator that acts directly on vascular smooth muscle to cause a reduction in peripheral vascular resistance and reduction in blood pressure The contractile processes of cardiac muscle and vascular smooth muscle are dependent upon the movement of extracellular calcium ions into these cells through specific ion channels. Amlodipine inhibits calcium ion influx across cell membranes selectively, with a greater effect on vascular smooth muscle cells than on cardiac muscle cells Following administration of therapeutic doses to patients with hypertension, amlodipine produces vasodilation resulting in a reduction of supine and standing blood pressures.
Calcium Channel Blockers Lower Blood Pressure by:
- Inhibiting calcium ion influx across cell membranes selectively, with a greater effect on vascular smooth muscle cells than on cardiac muscle cells
- Acting directly on vascular smooth muscle to cause a reduction in peripheral vascular resistance
- Producing vasodilation resulting in a reduction of supine and standing blood pressures 2 2
From the Research
Mechanism of Action
- Calcium channel blockers (CCBs) lower blood pressure by blocking calcium influx through voltage-dependent L (long-acting) channels without affecting calcium release from the sarcoplasmic reticulum 3
- The effect of blocking these channels is a decrease in the intracellular calcium concentration, which reduces vascular smooth muscle tone 3
- The subsequent decrease in peripheral resistance causes a decrease in systemic blood pressure 3
Effects on the Cardiovascular System
- CCBs also decrease myocardial contractility, which decreases myocardial oxygen consumption 3
- Overall, the CCBs at therapeutic doses improve the efficiency of ventricular function 3
- CCBs reduce blood pressure across all patient groups, regardless of sex, race/ethnicity, age, and dietary sodium intake 4
Types of Calcium Channel Blockers
- There are two main types of CCBs: dihydopyridine and non-dihydropyridine; the first type is vascular selective 5
- Dihydropyrines are indicated for hypertension, chronic, stable and vasospastic angina 5
- Non-dihydropyridines have the same indications plus antiarrythmic effects in atrial fibrillation or flutter and paroxysmal supraventricular tachycardia 5
Additional Mechanisms
- CCBs may also reduce blood pressure by inhibiting vascular smooth muscle carbonic anhydrase I 6
- This inhibition ensures an adequate pH for calcium ions transport through the channels, resulting in vasodilation 6