Cardizem is a calcium channel blocker that has been proven to effectively control blood pressure over a 24-hour period and to maintain the tolerability of other diltiazem formulations. Calcium channel blocking agents modulate the transport of calcium into the cells of the heart and blood vessels. These drugs are helpful in alleviating angina pectoris due to coronary artery spasms and are also useful in chronic angina. Side effects include arrhythmia, coughing, skin rash, and slow heartbeat.