Calcium Channel Blockers: Drugs, Side Effects & Overdose

Instructor: Justine Fritzel

Justine has been a Registered Nurse for 10 years and has a Bachelor's of Science in Nursing degree.

In this lesson we will learn about the class of prescription drugs called calcium channel blockers. We will look at how these work, what side effects can occur, and the risk of overdose.

What are Calcium Channel Blockers?

Calcium channel blockers are a class of prescription drugs that are used to treat various conditions such as high blood pressure and chest pain.

The blood vessels in your body contract or relax, causing your blood pressure to increase or decrease. You have calcium in your body that enters the cells of the blood vessels and allows those vessels to contract. But if you have high blood pressure, your doctor may prescribe a calcium channel blocker to block the calcium from entering the cells of the blood vessels, which in turn causes the blood vessels to relax. When the blood vessels are relaxed, blood pressure is lowered and blood flow is improved.

You can think of the calcium channel blockers being like a police officer directing traffic. He directs which way the cars should go to keep the roadways open and flowing freely. In the same way, the calcium channel blockers are diverting the calcium to prevent it from entering the cells. This allows for better blood flow and decreased blood pressure.

This same analogy may help you to understand why relaxation of the blood vessels results in decreased blood pressure. Think about that same traffic jam; if the cars are lined up tightly, they are moving slowly and pressure is building! Blood vessels function the same way. If the blood vessels are contracted, there is increased pressure that they are trying to push the blood through. If the traffic director blocks the 'calcium' from entering the cells, thereby resulting in relaxed blood vessels, the 'streets' become wider and allow cars to travel more easily.

A number of different medications are classified as calcium channel blockers. Several of these medications you can easily identify because they end in 'dipine'. Examples include nifedipine, amlodopine, and nicardipine. Unfortunately, this doesn't work for all calcium channel blockers. Other examples include verapamil and diltiazem.

Side Effects of Calcium Channel Blockers

Although there are benefits to taking calcium channel blockers, just like with any medication, side effects may also occur. We discussed how these medications work earlier. The actions that make these medications effective can also create side effects. These include having too low of blood pressure, slow heart rate, feeling lightheaded, and feeling drowsy.

Additional side effects can include increased appetite, swelling of the lower legs, constipation, bleeding of the gums, and reflux. Tell your doctor if you are having new symptoms since taking your calcium channel blocker.

What Happens if I Take Too Much?

Calcium channel blockers can be toxic if excessive amounts are taken. An overdose can be fatal. There are different forms of calcium channel blockers that range from immediate release pills to extended release pills. The type of pill determines the onset of complications from taking an excessive dose.

If you have taken an excessive dose, you will present with some of the side effects we discussed above, such as low blood pressure, swelling, and dizziness, but these will be more significant than just mild side effects. You will likely feel weak, may experience heart palpitations and chest pain, and you may pass out. You might become sweaty but flushed, confused, or short of breath and you may experience headaches, nausea, and vomiting.

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