A Pharmacology Review of Calcium Channel Blockers

• Calcium channel blockers, also known as calcium channel antagonists, are the drugs most commonly used in cardiovascular diseases. 
• We can classify calcium channel blockers into three classes based on their chemical structure. Each class has a different pharmacokinetic profile and clinical indications. 
• As a nurse, you play an essential role in getting the patient set on any therapy. 

Calcium Channel Blockers

Calcium channel blockers, also known as calcium channel antagonists, are the drugs most commonly used in cardiovascular diseases. They affect the movement of calcium through calcium channels.  

Here in this article, we will tell you the pharmacology of calcium channel blockers.  

Uses for Calcium Channel Blockers

Calcium channel blockers are used in the following scenarios: 

• To treat essential hypertension 
• To treat and prophylaxis of angina pectoris (vasospastic, chronic stable, unstable) or coronary artery spasm 
• For the prevention or control of supraventricular tachyarrhythmias 
• For the prevention of neurologic damage because of subarachnoid hemorrhage 
• In the management of hypertension (amlodipine, diltiazem, felodipine, isradipine, nicardipine, nifedipine, nisoldipine, verapamil) 
• Nimodipine- to prevent neurologic damage because of certain types of cerebral vasospasm.
  

You can also give calcium channel blockers in angina.  

These drugs are useful because you can administer them to patients having diabetes, asthma, or peripheral vascular disease as they do not worsen the pre-existing condition, unlike beta blockers.  

In atrial fibrillation, diltiazem and verapamil can be given. 

Classes of Calcium Channel Blockers

We can classify calcium channel blockers into three classes based on their chemical structure. Each class has a different pharmacokinetic profile and clinical indications.  

Diphenylaklamines

e.g.: verapamil that has significant effects on both cardiac and vascular smooth muscle cells.  

It is used to treat: 

• Angina  
• Supraventricular tachyarrhythmias 
• To prevent migraine and cluster headaches. 

Benzoithiazepines

e.g.: diltiazem. It has a less pronounced negative inotropic effect on the heart, compared to that of verapamil.  

They are used to treat 

• Hypertension  
• Arrhythmias 
• Angina  

Dihydropyridines

e.g.: nifedipine, amlodipine, felodipine, isradipine, nicardipine, and nisoldipine. They have a different pharmacokinetic profile, drug interactions, and approved uses compared to other calcium channel blockers.  

Moreover, they have a greater affinity for vascular calcium channels, compared to that of the heart. It makes them favourable to treat hypertension when a reduction in systemic vascular peripheral resistance is desired.  

Dihydropyridines interact less with other cardiovascular drugs, such as warfarin and digoxin. Often they are used concomitantly with calcium channel blockers.  

Mechanism 0f Action

The intracellular concentration of calcium plays an essential role in the maintenance of smooth muscle tone and myocardium contraction.  

Calcium channel blockers work by blocking the inward movement of calcium ions by binding to L- type calcium channels in the heart and the smooth muscles of the coronary and peripheral arteriolar vasculature.  

Due to this, vascular smooth muscles relax. Hence, the arteries dilate.  

Moreover, they also depress the rate of sinus node pacemaker, slow AV conduction, decrease heart rate, and produce negative inotropic effects. However, calcium channel blockers do not dilate veins.    

Calcium channel antagonists decrease coronary vascular resistance, increase coronary blood flow, and reduce myocardial oxygen demand. However, the degree of action varies with each drug in the class.

Adverse Reactions

The adverse reactions of calcium channel blockers are: 

• Orthostatic hypotension 
• Heart failure 
• HypotensionArrhythmias, such as bradycardia and AV block 
• Dizziness 
• Headache 
• Flushing 
• Weakness 
• Persistent peripheral edema 
• Nifedipine and other dihydropyridines might cause gingival hyperplasia. 
• Verapamil poses a risk of first-degree atrioventricular block and constipation. These both are dose-dependent side effects of Verapamil.  

Clinical Considerations

As a nurse, you need to keep the following things in mind with calcium channel blockers therapy: 

• Monitor the patient’s blood pressure frequently.  
• Keep an eye on the patient’s weight and assess them for any symptoms of heart failure, such as dyspnea, rales/crackles, weight gain, peripheral edema, and jugular venous distention. 
• In patients with angina, assess the severity and frequency of chest pain periodically with their intake.  
• In patients with arrhythmias, monitor ECG continuously with IV therapy and periodically with long-term diltiazem, and verapamil therapy is given orally.  
• With nimodipine for cerebral vasospasm, assess the patient’s neurological status, such as level of consciousness and movement before and during the therapy, and periodically.  

Patient Education

As a nurse, tell the patient and their family about various points to keep in mind with calcium channel blockers therapy.  

Ask them to: 

• Take the medication even if they feel well and have no symptoms of angina or other cardiovascular diseases. 
• Not to crush the sustained release tablet.  
• Move slowly, especially when standing up from lying down, to minimize orthostatic hypotension. 
• Maintain oral hygiene and visit the dentist often for oral cavity cleaning. The patients should report to the healthcare provider if they notice bleeding, tenderness, and gingival hyperplasia.  
• Emphasize attending follow-up visits so that you can monitor their progress.
  

The Bottom Line

As a nurse, you play an essential role in getting the patient set on any therapy. With calcium channel blockers, evaluate the patient for the following parameters:

• They maintain an adequate cardiac output.  
• The patient complains about no adverse reactions and complies with the therapy. 
  

You must tell them to report to you if they notice any adverse drug reaction, do not feel well, or if their blood pressure remains elevated. 

Read More