A Closer Look at Heart Medication Verapamil

Verapamil is a medication used to treat heart disease. It works by relaxing the blood vessels of the heart, as well as the blood vessels throughout the body. If you are prescribed verapamil, it's a good idea for you to familiarize yourself with the condition that you are being treated for, as well as the side effects of this medication.

Mechanism of Action

Verapamil is a calcium channel antagonist (blocker). Calcium promotes vascular muscle contraction, which narrows the blood vessels and increases pressure in the heart.

Verapamil relaxes muscles that are located in the blood vessels by decreasing the entry of calcium ions through the L-type calcium channels that are located in these muscles.

Verapamil has several effects:

• Vasodilation (widening) of coronary arteries (arteries that supply the heart muscle) and widening of arteries throughout the body
• Decreases intensity of heart contraction (heart pumping)
• Slows heart rate

All of the different uses for verapamil are related to these effects.

Metabolism

Verapamil is absorbed in the intestines and approximately half of it is used or eliminated from the body in about eight hours.

Clinical Uses

Verapamil is indicated for the treatment of:

• Hypertension (high blood pressure), including malignant or refractory hypertension
• Arrhythmias (irregular heart rates) such as atrial flutter, atrial fibrillation, and supraventricular tachycardia
• Angina (chest pain), including stable angina, unstable angina, and Prinzmetal's

Verapamil is also used off-label for treating certain conditions that are associated with muscle contraction of the blood vessels.

A few of the off-label uses:

• Raynaud's phenomenon
• Migraine prophylaxis
• Cluster headache prophylaxis

Adverse Effects and Drug Interactions

The most frequent adverse effect of verapamil is constipation. For some people, verapamil can cause dizziness, light-headedness, and hypotension (low blood pressure).

In cases of overdose, verapamil may interfere with heart rhythm, which can be fatal.

Verapamil can interact with a wide variety of other drugs, including:

• Verapamil used with beta-blockers, nitrates, or diuretics can cause your blood pressure to fall dangerously low.
• Verapamil can interact with statins, which are used to treat high cholesterol. Verapamil can cause an increase in the concentration of statins in the body; thus, if you are already taking a statin, be sure to let your doctor know so your statin dose can be adjusted if needed.
• Verapamil is metabolized by the cytochrome P450 enzymes and the use of certain prescription medications like amiodarone (another antiarrhythmic) can interfere with P450, leading to verapamil toxicity.

Grapefruit juice affects the P450 system and may increase verapamil blood concentrations.

If you or a loved one is taking verapamil, it's important to be closely monitored by your prescribing cardiologist. Make appointments for regular check-ups with your cardiologist and be sure to inform them of any changes in your medication regimen—including any use of herbal medications.

If you are feeling any adverse effects, like fainting, call for emergency help.