Calcium-channel blockers -- sometimes called calcium antagonists -- work by reducing the uptake of calcium into the muscles of the heart and arteries. Because muscles require calcium to contract, reducing the availability of calcium relaxes arterial muscles and allows the arteries to open wider, which reduces blood pressure.
Felodipine is also available in combination with enalapril, an angiotensin-converting enzyme (ACE) inhibitor, as a treatment for high blood pressure. This combination therapy is marketed as Lexxel.
Felodipine has been studied for its use in heart failure by numerous researchers, and has been found to have no quality of life or survival benefit for that condition. Calcium-channel blockers like felodipine can also cause fluid retention, which is particularly dangerous in patients with heart failure. For patients with heart failure, most doctors prescribe other drugs like ACE inhibitors or beta blockers.
Although felodipine is generally well tolerated, side effects do occur in some patients. These may include swelling in the lower legs and feet, irregular heartbeat, headache, dizziness, upset stomach, swelling of the gums and flushing. It is not known if felodipine is safe for use by pregnant women or nursing mothers. Grapefruit and grapefruit products can interact with felodipine; therefore, patients taking felodipine are advised to avoid all grapefruit products.
There is some concern among medical experts about overdoses of calcium-channel blockers like felodipine. These overdoses are considered one of the leading causes of prescription drug deaths. Over 9,500 cases of calcium-channel blocker overdoses were reported to poison control centers in 2002. Toxic levels of calcium-channel blockers, whether brought about by intentional or accidental overdosing, can cause heart attacks, shock and sudden cardiac collapse.
Though felodipine and other calcium-channel blockers have been used to treat high blood pressure in patients with metabolic syndrome (a group of conditions associated with heart disease), research presented in 2008 finds that diuretics are less costly and more effective, especially among African-American patients.
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