What is verapamil, and how does it work (mechanism of action)?
Verapamil belongs to a class of medications called calcium channel blockers (CCBs), which includes amlodipine (Norvasc), diltiazem (Cardizem, Dilacor), nifedipine (Adalat, Procardia) as well as others. These medications block the movement of calcium into the muscle cells of the coronary arteries (the arteries supplying the heart with blood) as well as the other arteries of the body. Since calcium triggers contraction of muscles, blocking entry of calcium relaxes the muscles that surround the arteries. This relaxation allows 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 muscles in the arteries of 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). 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.
What brand names are available for verapamil?
Calan, Verelan, Verelan PM,
Is verapamil available as a generic drug?
GENERIC AVAILABLE: Yes
Do I need a prescription for verapamil?
Yes
What are the uses for verapamil?
Verapamil is prescribed for the prevention and treatment of heart pain (angina), high blood pressure (hypertension), and abnormally fast heart rhythms such as atrial fibrillation. It is also used off-label for preventing migraine headaches.
What are the side effects of verapamil?
Common side effects of Verapamil are
- 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,
- nausea, and
- constipation.
Verapamil also can cause mildly abnormal liver tests that usually return to normal with discontinuation of the medication. Verapamil may reduce 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.
What is the dosage for verapamil?
Verapamil can be taken with food.
- Angina (immediate release formulations): 80-160 mg three times daily. Angina (extended release formulations): 180-540 mg at bedtime.
- Hypertension (immediate release): 80-320 mg twice daily. Hypertension (extended release): 120-480 mg once or twice daily depending on the brand.
- Migraine: 160-320 mg three to four times daily.
Which drugs or supplements interact with verapamil?
Concurrent use of verapamil with a beta blocker (another class of medications that slow heart rate) can cause profound and dangerous reductions in heart rate. Verapamil can raise the levels of some drugs in blood including digoxin (Lanoxin), theophylline (Slo-Bid), cyclosporin, and carbamazepine (Tegretol). Therefore, monitoring of the levels of these drugs is important to avoid toxicity.
Verapamil may reduce blood levels of lithium (Eskalith, Lithobid) 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.
The use of "statins" (for example, simvastatin or lovastain) in combination with verapamil has been associated with reports of myopathy/rhabdomyolysis because verapamil reduces the break down of these statins in the liver. The dose of simvastatin in patients on verapamil should not exceed 10 mg daily and the dose of lovastatin (Mevacor, Altoprev) should not exceed 40 mg daily. Lower starting and maintenance doses of other statins (for example, atorvastatin [Liptor]) may be required since verapamil also may increase the plasma concentration of these drugs also. Rifampin and phenobarbital increase the elimination of verapamil, potentially reducing the effect of verapamil.
Is verapamil safe to take if I’m pregnant or breastfeeding?
Safety of verapamil during pregnancy has not been established. Verapamil crosses the placenta and enters the fetus.
Safety in nursing mothers has not been established. Verapamil is excreted in human milk.
What else should I know about verapamil?
What preparations of verapamil are available?
Immediate release tablets: 40, 80, and 120 mg; sustained release caplets: 120, 180, 240,and 360 mg; extended release tablets: 100, 120, 180, 200, 240, and 300 mg; Injection: 2.5 mg/mL
How should I keep verapamil stored?
Verapamil should be stored at room temperature 15 C – 30 C (59 F – 86 F) in a tight, light- resistant container.