Calcium channel blocker

• Calcium channel blockers (CCBs) are a class of medications that inhibit the entry of calcium ions into cells by blocking calcium channels.
• These medications primarily target calcium channels in cardiac and smooth muscle cells, leading to various therapeutic effects.
• Calcium channel blockers are commonly used to treat conditions such as hypertension (high blood pressure), angina (chest pain), and certain cardiac arrhythmias.

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Calciumkanal Förstermann

Dipines

Verapamil skeletal

Mechanism of Action

• Calcium channel blockers exert their effects by blocking L-type calcium channels in cell membranes.
• These channels are responsible for allowing calcium ions to enter cells, particularly cardiac and smooth muscle cells.
• By inhibiting the influx of calcium ions, calcium channel blockers reduce the intracellular calcium concentration, leading to the following effects:

1. Vasodilation: Calcium channel blockers cause relaxation of vascular smooth muscle, leading to dilation of arteries and arterioles. This reduces peripheral vascular resistance and lowers blood pressure.
2. Negative Inotropic Effect: By decreasing the entry of calcium ions into cardiac muscle cells, calcium channel blockers reduce myocardial contractility, resulting in a negative inotropic effect. This reduces the force of contraction of the heart, thereby decreasing oxygen demand and relieving angina symptoms.
3. Negative Chronotropic Effect: Calcium channel blockers also decrease the rate of spontaneous depolarization in the sinoatrial (SA) node of the heart, reducing heart rate. This negative chronotropic effect can be beneficial in certain cardiac arrhythmias.

Types of Calcium Channel Blockers

There are different types of calcium channel blockers, classified based on their predominant effects on calcium channels:

• Dihydropyridines (DHPs): DHPs predominantly act on peripheral arterioles and cause potent vasodilation. They have minimal effects on the heart. Examples of DHPs include amlodipine, nifedipine, and felodipine.
• Non-Dihydropyridines (Non-DHPs): Non-DHPs have effects on both peripheral arterioles and the heart. They not only cause vasodilation but also have negative inotropic and negative chronotropic effects. Examples of non-DHPs include verapamil, a phenylalkylamine, and diltiazem, a benzothiazepine.

Examples of Calcium Channel Blockers

• There are several calcium channel blockers available, including:

Dihydropyridines (DHPs):

• Amlodipine
• Nifedipine
• Felodipine
• Nicardipine
• Isradipine

Non-Dihydropyridines (Non-DHPs):

• verapamil, a phenylalkylamine, and diltiazem, a benzothiazepine

• These examples represent commonly prescribed calcium channel blockers, but there are other agents available as well. Each calcium channel blocker may have specific characteristics and indications, and the choice of medication depends on the individual patient's condition and needs.

Medical Uses

Calcium channel blockers are used to treat various cardiovascular conditions, including:

• Hypertension: Calcium channel blockers are effective in lowering blood pressure and are commonly used as first-line or second-line agents for the treatment of hypertension.
• Angina: Calcium channel blockers are used to relieve angina symptoms by reducing myocardial oxygen demand through their negative inotropic and vasodilatory effects.
• Cardiac Arrhythmias: Non-DHP calcium channel blockers, such as verapamil and diltiazem, are used in the treatment of certain cardiac arrhythmias, including supraventricular tachycardia and atrial fibrillation.
• Raynaud's Phenomenon: Calcium channel blockers, particularly DHPs, can be helpful in relieving symptoms of Raynaud's phenomenon by promoting peripheral vasodilation.

Adverse Effects

Common adverse effects associated with calcium channel blockers include:

• Hypotension: Due to their vasodilatory effects, calcium channel blockers can cause low blood pressure, resulting in dizziness, lightheadedness, and even fainting.
• Bradycardia: Non-DHP calcium channel blockers can reduce heart rate, leading to bradycardia (slow heart rate).
• Peripheral Edema: DHP calcium channel blockers, such as amlodipine, may cause peripheral edema (swelling of the feet and ankles) due to their vasodilatory effects.
• Constipation: Verapamil and diltiazem, non-DHP calcium channel blockers, can cause constipation.

• Individuals may experience other less common adverse effects, which can vary depending on the specific calcium channel blocker used.

Contraindications

• While calcium channel blockers are generally well-tolerated, there are certain contraindications to consider. Contraindications are specific circumstances or conditions in which the use of a particular medication is not recommended due to potential risks.

Here are some common contraindications for calcium channel blockers:

• Hypersensitivity or Allergy: Individuals who have a known hypersensitivity or allergy to a specific calcium channel blocker should avoid its use.
• Severe Hypotension: Calcium channel blockers can cause a decrease in blood pressure. Therefore, they should be used with caution or avoided in individuals with severe hypotension (low blood pressure).
• Cardiogenic Shock: Calcium channel blockers are contraindicated in individuals with cardiogenic shock, a condition characterized by a severe decrease in heart function that leads to insufficient blood flow to the body's organs.
• Sick Sinus Syndrome: Calcium channel blockers, especially non-DHPs, can further slow the heart rate in individuals with sick sinus syndrome, a condition characterized by abnormal functioning of the sinus node in the heart.
• Second- or Third-Degree Atrioventricular Block: Calcium channel blockers, particularly non-DHPs, can further impair the conduction of electrical impulses in individuals with advanced atrioventricular block.
• Acute Myocardial Infarction: Non-DHP calcium channel blockers, such as verapamil and diltiazem, are generally contraindicated during the acute phase of myocardial infarction (heart attack) due to their negative inotropic effects.

• It's important to note that contraindications may vary depending on the specific calcium channel blocker and individual patient factors. Therefore, it is crucial to consult with a healthcare professional for personalized advice regarding the use of calcium channel blockers and any contraindications that may apply.

Drug Interactions

Calcium channel blockers may interact with other medications, including:

• Beta Blockers: Concurrent use of calcium channel blockers and beta blockers can have an additive effect on reducing heart rate and blood pressure. Careful monitoring is necessary when these medications are used together.
• Grapefruit Juice: Grapefruit juice can inhibit the metabolism of certain calcium channel blockers, leading to increased blood levels of the medication and a higher risk of adverse effects. It's generally recommended to avoid consuming grapefruit juice when taking calcium channel blockers.
• CYP3A4 Inhibitors and Inducers: Some calcium channel blockers, such as verapamil and diltiazem, are metabolized by the CYP3A4 enzyme. Medications that inhibit or induce CYP3A4 can affect the metabolism and blood levels of these calcium channel blockers, potentially requiring dosage adjustments.

• It's essential to inform healthcare professionals about all medications, including prescription drugs, over-the-counter medications, and supplements, to minimize the risk of potential drug interactions when using calcium channel blockers.

See Also

• Antihypertensive Medications
• Angina
• Cardiac Arrhythmias
• Hypertension

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