Many patients may hear that the medication that their doctor is prescribing them is a sodium channel blocker, Beta-blocker, potassium channel blocker, or a calcium channel blocker without being told what the difference is or why or how they work so well. Patients may be wondering...is Beta the letter of my fraternity that has come back to haunt me after all these years? As shown in the previous blog and will be further represented in this blog, sodium, "Beta", potassium and calcium are not some evil little molecules out to get your heart. They are very vital aspects of your bodily functions but can sometimes become overstimulated, cause arrhythmias and those funky channel blockers become just what the doctor orders. In the previous blog, I reviewed Sodium and Beta channel blockers. Here I will discuss Potassium and Calcium Channel blockers.
Class III: Potassium Channel Blockers
Action Potentials and the Role Potassium Plays in Action Potentials
Remember the action potentials discussed with the sodium channels? The beginning of the action potential starts with the depolarization of the cell membrane when sodium rushes in. The cell begins to repolarize when potassium leaves the cell, although not as quickly as the sodium rushes in. This repolarization brings the cell membrane back down to a more negative resting potential.
What a Potassium Channel Blocker Blocks and What They are Used for Treating
Potassium Channel Blockers bind to and block the potassium channels that are responsible for the cell membrane repolarization. Blocking these channels slows (delays) repolarization, which leads to an increase in action potential duration and an increase in the effective refractory period. An increase in the refractory period means the period of time that the cell is unexcitable and therefore cannot receive another action potential is prolonged. On an electrocardiogram, this delay of the depolarization increases the QT interval.
By making the cell less excitable, Potassium Channel Blockers are very effective in treating tachycardias. They are also known to treat supraventricular and ventricular arrythmias, atrial fibrillation, and atrial flutter.
Examples of Potassium Channel Blockers and Their Side Effects
Amiodarone, Dronedarone, Bretylium, Ibutilide, Dofetilide
The side effects of Potassium Channel Blockers are to produce a type of ventricular tachycardia, bradycardia and atrioventricular block or SA node dysfunction. Talk with your doctor and your pharmacist to find out what the right drug is for you. And don't forget to rate the drug on www.RateaDrug.com to let others know what experiences you had with a specific medication!
Class IV: Calcium Channel Blockers
What are Calcium Channels and Where are They Found
Calcium channels are cells known as "excitable cells" that are sensitive to electrical impulses. Like the sodium and potassium channels, when the proteins receive the correct signal, the channel opens, allowing calcium to flow across the channel. The small charge that the calcium ion carries can stimulate muscle contractions, hormone release or firing of a neurotransmitter. Therefore, calcium channels are found in muscles, glial cells and neurons.
What a Calcium Channel Blocker Blocks and What They are Used for Treating
Calcium Channel Blockers dilate the arteries in the heart, reducing blood pressure in the arteries which leads to the heart being able to pump blood more easily. Essentially the heart's need for oxygen to pump the heart is lowered because it does not need to pump as often.
Calcium channel blockers are often used for high blood pressure, chest pain (due to lack of oxygen in the heart), and arrhythmias such as atrial fibrillation, and supraventricular tachycardia. They can be used after a heart attack for a patient that is not a good candidate for beta-blockers. Unfortunately, calcium channel blockers have not been shown to prevent future heart attacks.
Examples of Calcium Channel Blockers and Their Side Effects
Amlodipine, Diltiazem (Brand=Cardizem), Felodipine, Nifedipine, Nicardipine, Nimodipine, Nisoldipine, Verapamil
The most common side effects of Calcium Channel Blockers are constipation, nausea, headache, rash, swelling, low blood pressure, drowsiness and dizziness. In addition, liver dysfunction, sexual dysfunction and overgrowth of gums may occur. Talk with your doctor and your pharmacist to find out what the right drug is for you. And don't forget to rate the drug on www.RateaDrug.com to let others know what experiences you had with a specific medication!
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