Knowledge of calcium channel blockers.📓📓📓

Calcium channel blockers are one of the most commonly used
antihypertensive drugs in clinical practice. It has been used for many years. Its efficacy and safety have been proven. It plays an important role in the clinical treatment of cardiovascular disease. Therefore, for calcium channel blockers, you should have the following knowledge.

Mechanism of action of calcium channel blockers.

There are two types of calcium channel blockers: dihydropyridines and non-dihydropyridines. The pharmacological effects of both of them are to inhibit the influx of calcium ions into vascular smooth muscle cells by selectively blocking voltage-dependent calcium ion channels. This relaxes the smooth muscle of the blood vessels, which dilates the blood vessels. Peripheral vascular resistance will therefore decrease, to achieve a blood pressure lowering effect. They mainly dilate the arteries, especially the coronary arteries.

• Dihydropyridine calcium channel blockers have better vascular selectivity. It generally does not affect atrioventricular conduction, sinoatrial node function, and myocardial contractility at therapeutic doses.
• Non-dihydropyridine calcium channel blockers have poor vascular selectivity. It has a negative inotropic effect and negative conduction on the heart. Therefore, it not only lowers blood pressure but also lowers heart rate.

Calcium channel blockers commonly used in clinical practice.

Dihydropyridine calcium channel blockers:

Drug	Drug standard (mg)	Dosage (initial dose to full dose, mg/d)	Times of taking medicine (times/d)
Amlodipine	5、10	5 to 10	1
Barnidipine	5、10、15	5 to 15	1
Benidipine	2	4 to 8	1
Cilnidipine	5、10	5 to 10	1
Felodipine	2.5、5	2.5 to 10	2
Lacidipine	4	4 to 8	1
Lercanidipine	10	10 to 20	1
Levamlodipine	2.5、5	2.5 to 5	1
Manidipine	5	5 to 20	1
Nicardipine	20	40 to 80	2 to 3
Nifedipine	5、10	10 to 30	2 to 3
Nifedipine (Sustained Release)	20、30	10 to 80	2
Nifedipine (Controlled Release)	30	30 to 60	1
Nitrendipine	10	20 to 60	2 to 3

Non-dihydropyridine calcium channel blockers:

Drug	Drug standard (mg)	Dosage (initial dose to full dose, mg/d)	Times of taking medicine (times/d)
Diltiazem	30	90 to 360	1 to 2
Diltiazem (Sustained release)	200	200	1
Verapamil	40	80 to 480	2 to 3
Verapamil (Sustained release)	240	120 to 480	1 to 2

Characteristics of calcium channel blockers.

Their pharmacodynamics are dose-dependent and have a good antihypertensive effect. Single-agent therapy generally achieves the desired effect. Mild to moderate hypertension can generally be controlled by it. They are the first-line treatment in many national hypertension guidelines.

Stroke risk in hypertensive patients is significantly reduced by calcium channel blockers.

Many clinical studies have shown that calcium channel blockers can change the physiological activities related to calcium ions to affect atherosclerosis. They can slow the progression of atherosclerosis

Calcium channel blockers do not alter sugar and lipid metabolism. Therefore, it can be used by patients with diabetes and metabolic syndrome. In addition, levamlodipine besylate can dilate the bulbar arterioles and afferent arterioles. It reduces the resistance of the renal blood vessels without increasing the intra-glomerular pressure. These factors make it beneficial for hypertensive patients with diabetes mellitus and patients with parenchymal renal disease.

Calcium channel blockers have the effect of increasing sodium excretion. If the patient has salt-sensitive hypertension, its antihypertensive effect will be better. Its antihypertensive effect is not affected by a high-salt diet, so it is also suitable for people on a high-salt diet.

Calcium channel blockers have a good effect on volume hypertension such as isolated systolic hypertension and elderly hypertension.

Medium- and long-acting calcium channel blockers have a good safety profile, fewer side effects, and a lower incidence of hypotension. Their effects are gentle and long-lasting. Most only need to take 1 or 2 pills a day. This can improve patient compliance with medication and the efficacy of treatment.

Calcium channel blockers dilate the coronary arteries, thereby reducing coronary resistance and improving the ability of the heart muscle to supply blood. It can treat coronary heart disease, angina pectoris, hypertrophic cardiomyopathy and peripheral vascular disease, especially for variant angina pectoris caused by coronary spasm.

Non-dihydropyridine calcium channel blockers can also slow the heart rate and improve blood supply to the coronary arteries. It can prevent and treat coronary heart disease, arrhythmias such as premature atrial beats, and supraventricular tachycardia.

Indications for calcium channel blockers.

Calcium channel blockers are used for various types of high blood pressure. It is the first-line treatment for high blood pressure.

Dihydropyridine calcium channel blockers:

• Hypertension with atherosclerosis: Peripheral vascular disease, coronary atherosclerosis, carotid atherosclerosis or stable angina with hypertension.
• Volumetric hypertension: Hypertension with low sympathetic or low renin activity, isolated systolic hypertension and elderly hypertension.

Non-dihydropyridine calcium channel blockers:

• Angina pectoris, supraventricular tachycardia, carotid atherosclerosis with hypertension.

Combination medication.

Diuretics: The risk of stroke in hypertensive patients can be reduced by combining calcium channel blockers with diuretics. However, the hypotensive effect of calcium channel blockers reflexively activates sympathetic nerves. Diuretics also activate sympathetic nerves after reducing blood volume. Their side effects may be aggravated by this.

Angiotensin-converting enzyme inhibitors or angiotensin II receptor antagonists: They dilate arteries and veins. Calcium channel blockers can directly dilate the arteries. Therefore, their combined use will have a synergistic effect. Angiotensin-converting enzyme inhibitors or angiotensin II receptor antagonists can partially inhibit the side effects of increased heart rate and increased reflex sympathetic tone caused by calcium channel blockers. Ankle edema is a common side effect of dihydropyridine calcium channel blockers, which can be eliminated or alleviated by angiotensin-converting enzyme inhibitors or angiotensin II receptor antagonists.

β-blockers: It can inhibit the blood volume mechanism and sympathetic nerve, and achieve a significant antihypertensive effect. The reflex sympathetic excitation caused by vasodilation by calcium channel blockers is inhibited by β-blockers. The increase in peripheral arterial resistance caused by long-term use of β-blockers is also inhibited by calcium channel blockers. They are suitable for patients with angina pectoris, heart failure, tachycardia, myocardial infarction with hypertension.

Side effects of calcium channel blockers.

Edema: It is a common side effect of calcium channel blockers. Edema of the face, lower extremity pretibial, lower extremity pretibial edema may occur. It will improve after stopping the drug. Alternatively, it may try to replace the patient with other calcium channel blockers. The incidence of side effects with levamlodipine is relatively low.

Gingival hyperplasia: It may occur in patients taking calcium channel blockers for a long time. Among them, nifedipine caused the highest incidence of gingival hyperplasia.

Hypotension: Some calcium channel blockers, especially short-acting calcium channel blockers, may lower blood pressure too quickly and cause hypotension. Therefore, it recommends the use of long-acting calcium channel blockers (eg, amlodipine) to lower blood pressure. The patient's blood pressure should also be monitored after taking the drug.

Atrioventricular block: Non-dihydropyridine calcium channel blockers have negative effects on the heart. It inhibits sinus node and myocardial contraction. The main clinical manifestation is atrioventricular block. Therefore, patients with sick sinus syndrome and 2nd degree or higher atrioventricular block are contraindicated.

Heart failure: Calcium channel blockers dilate systemic blood vessels, reduce cardiac load and protect ischemic myocardium. However, the degree of heart failure can be aggravated, so it should be used with caution in patients with heart failure.

Tachycardia: Calcium channel blockers reflexively activate the sympathetic nervous system. It increases the heart rate. When necessary, calcium channel blockers should be combined with β-blockers to alleviate this adverse effect.

Headache and flushing: The dilation of blood vessels caused by calcium channel blockers may cause headaches and flushing. If the patient cannot tolerate it, other antihypertensive drugs should be used.

Constipation: Intestinal smooth muscle calcium transport may also be affected, resulting in constipation. If the constipation is more severe, it may consider changing the dressing or adding a laxative.

Caution with calcium channel blockers.

Short-acting nifedipine: It may drop blood pressure too quickly and cause low blood pressure. It will also increase the heart rate reflex reflex, blood pressure fluctuations and other problems. Therefore, it is mainly used in the clinical treatment of coronary heart disease and angina pectoris, and it can be sucked in the first aid.

Pay attention to the method of administration: Sustained-release or controlled-release tablets should be swallowed whole.

Avoid grapefruit or grapefruit juice: The activity of the CYP3A4 enzyme can be inhibited by grapefruit. In addition to no obvious effect on amlodipine, other metabolic rates will be reduced, thereby enhancing drug efficacy and the occurrence of adverse reactions.