Are there any differences among calcium channel blockers?
Calcium channel blockers differ in their duration of action, the process by which they are eliminated from the body, and, most importantly, in their ability to affect heart rate and contraction. Some calcium channel blockers (for example, amlodipine [Norvasc]) have very little effect on heart rate and contraction so they are safer to use in individuals who have heart failure or bradycardia (a slow heart rate). Verapamil (Calan, Isoptin) and diltiazem (Cardizem) have the greatest effects on the heart and reduce the strength and rate of contraction. Therefore, they are used in reducing heart rate when the heart is beating too fast.
With which drugs do calcium channel blockers interact?
Most of the interactions of calcium channel blockers occur with verapamil (Calan, Isoptin) or diltiazem (Cardizem). The interaction occurs because verapamil and diltiazem decrease the elimination of a number of drugs by the liver. Through this mechanism, verapamil and diltiazem may reduce the elimination and increase the blood levels of carbamazepine (Tegretol), simvastatin (Zocor), atorvastatin (Lipitor), and lovastatin (Mevacor). This can lead to toxicity from these drugs.
Grapefruit juice (approximately 200 ml) may elevate blood concentrations of felodipine (Plendil), verapamil (Calan, Isoptin), nisoldipine (Sular), nifedipine (Adalat, Procardia), nicardipine (Cardene), and possibly amlodipine (Norvasc). Grapefruit juice should not be consumed within 2 hours before or 4 hours after administration of affected calcium channel blockers.
Reference: FDA Prescribing Information
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