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GENERIC NAME: verapamil
BRAND NAMES: Calan, Verelan, Verelan PM, Isoptin, Isoptin SR, Covera-HS
DRUG CLASS AND MECHANISM: Verapamil belongs to a class of medications called calcium channel blockers. These medications block the movement of calcium into the muscle cells of the coronary arteries (the arteries supplying the heart) as well as the other arteries of the body. Since calcium is what triggers contraction of muscles, blocking entry of calcium relaxes the arterial muscles. This relaxation allows the arteries to become larger so that more blood can flow through them. Thus, verapamil is useful in treating and preventing chest pain (angina) resulting from spasm (contraction) of the coronary arteries that reduces the flow of blood to the heart. Relaxing the muscles lining the arteries in the rest of the body lowers blood pressure and thereby reduces the pressure against which the heart must pump blood. As a result, the heart works less and requires less oxygen-carrying blood. This allows the heart to work with the reduced flow of blood caused by coronary artery disease and prevents angina (which occurs whenever the flow of blood to the heart is inadequate). For more detailed information related to coronary artery disease, please read the Chest Pain, Cholesterol, and Heart Attack articles. Verapamil also decreases the conduction of electrical impulses through the heart that control the coordination of contraction. As a result, the rate of contraction slows. Verapamil was approved by the FDA in March, 1982.
PREPARATIONS: Immediate release tablets: 40, 80, 120 mg; sustained release caplets: 120, 180, 240, 360 mg; extended release tablets: 100, 120, 180, 200, 240, 300 mg; Injection: 2.5 mg/mL
STORAGE: Store at room temperature 15° to 30°C (59° to 86°F) in tight, light- resistant container.
PRESCRIBED FOR: Chest pain (angina) occurs because insufficient oxygen-carrying blood is delivered to the muscles of the heart. Insufficient oxygen-carrying blood may be a result of blockage of blood flow in the coronary arteries due to coronary artery disease or spasm, or an increase in physical exertion that increases the workload of the heart and the demand by the heart for oxygen. Verapamil is used for the treatment and prevention of angina resulting from coronary artery disease and spasm as well as from exertion. Verapamil also is used in the treatment of high blood pressure. Verapamil slows electrical conduction of the electrical impulses through the heart and has been used to in treat 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.
DOSING: The usual oral dose is 180-480 mg/day. Verapamil may be given once, twice or three times daily depending on the formulation used. Verapamil can be taken with food.
DRUG INTERACTIONS: Concurrent use of verapamil with a beta blocker (another class of medications that slow heart rate) can occasionally cause profound and dangerous heart slowing.
Verapamil can raise the levels of some drugs in blood including digoxin (Lanoxin), theophylline (Slo-Bid), and carbamazepine (Tegretol). Therefore, monitoring of the levels of these drugs is important to avoid toxicity.
Verapamil may reduce blood levels of lithium in some patients. For unclear reasons some patients who took both verapamil and lithium have noticed increased side effects of lithium without increases in their blood levels of lithium.
PREGNANCY: Safety during pregnancy has not been established. Verapamil crosses the placenta and enters the fetus.
NURSING MOTHERS: Safety in nursing mothers has not been established. Verapamil is excreted in human milk.
SIDE EFFECTS: Side effects from verapamil generally are mild and transient. It can cause dizziness, weakness or fainting because of a slow heart rate or low blood pressure. Other side effects include swelling of the lower extremities, rash, headache, and constipation. Verapamil also can cause mildly abnormal liver tests that usually return to normal with discontinuation of the medication.
Verapamil may reduce the heart rate. Verapamil also can cause excessive lowering of blood pressure in rare instances. Verapamil can aggravate heart failure, especially in patients with poor function of their heart muscle. | |
