Verapamil belongs to a class of medications called calcium channel blockers. These medications block the transport of calcium into the smooth muscle cells lining the coronary arteries and other arteries of the body. Since calcium is important in muscle contraction blocking calcium transport relaxes artery muscles and dilates coronary arteries and other arteries of the body. By relaxing coronary arteries verapamil is useful in treating and preventing chest pain angina resulting from coronary artery spasm. Relaxing the muscles lining the arteries of the rest of the body lowers blood pressure which reduces the burden on the heart as it pumps blood to the body. Reducing heart burden lessens the heart muscles demand for oxygen and further helps to prevent angina in patients with coronary artery disease. For more detailed information related to coronary artery disease please read the Chest Pain Cholesterol and Heart Attack articles. Verapamil can decrease electrical conduction in the heart and slow heart rate.

Verapamil comes as a regular tablet and as an extended-release long-acting tablet and capsule to take by mouth. The regular tablet is usually taken three times a day. The extended-release tablet and capsule are usually taken one or two times a day and should be swallowed whole. Do not chew divide or crush the extended-release tablet or capsule. Follow the directions on your prescription label carefully and ask your doctor or pharmacist to explain any part you do not understand. Take verapamil exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Verapamil controls arrhythmias high blood pressure and chest pain angina but does not cure them. Continue to take verapamil even if you feel well. Do not stop taking verapamil without talking to your doctor

Side effects are generally mild and transient. Verapamil can cause difficulty breathing or wheezing as a result of worsening heart failure. It can cause dizziness weakness or fainting because of slow heart rate or low blood pressure. Other side effects include swelling of the lower extremities rash headache and constipation. Verapamil can also cause mildly abnormal liver tests that are generally reversible with discontinuation of the medication.

Verapamil may cause an upset stomach. Take verapamil with food or milk.

Talk to your doctor before using salt substitutes containing potassium. If your doctor prescribes a low-salt or low-sodium diet follow these directions carefully.

Chest pain angina occurs because insufficient oxygen is delivered to the heart muscles. Insufficient oxygen may be a result of a coronary artery blockage or spasm or because of physical exertion which increases heart oxygen demand in a patient with coronary artery narrowing. Verapamil is used for the treatment and prevention of angina resulting from coronary artery spasm as well as from exertion. Verapamil is also used in the treatment of high blood pressure. Verapamil slows electrical conduction in the heart. It has been used in treating abnormally fast heart rhythms such as atrial fibrillation and in the prevention of recurrent episodes of rapid heart rhythm originating from the atria. For further information about abnormal heart rhythms please read the Atrial Fibrillation and Palpitation articles.

Verapamil can be taken with food. Since verapamil is excreted by the kidney and metabolized by the liver dosages may need to be reduced in patients with liver or kidney dysfunction. Otherwise excess accumulation of verapamil in the body can cause profoundly slow heart rate and low blood pressure.

Store at room temperature in tight light- resistant container.

Verapamil slows heart electrical conduction and can cause a dangerously slow heart rate in patients with existing electrical conduction disease of the heart. Concurrent use of verapamil with a beta blocker another class of medications that slow heart rate can occasionally cause profound heart slowing. A small group of patients with irregular heart rhythms has a condition called Wolff-Parkinson-White WPW syndrome. Verapamil can cause a dangerously rapid heart rate in these individuals. Verapamil can aggravate heart failure especially in patients with poor ventricle muscle function. Verapamil can also cause excessive lowering of blood pressure in rare instances.

Concurrent administration of verapamil with digoxin Lanoxin theophylline Slo-Bid and carbamazepine Tegretol can increase blood drug levels of these other medications. Therefore monitoring of drug levels is important to avoid toxicity. Digoxin is commonly used in treating heart failure and fast heart rhythms. Theophylline is used in treating asthma. Carbamazepine is an anti-seizure medication. Safety in children has not been established.