Cardizem CDDiltiazemSanofi Aventis. Rx quality 90(3 x 30) Tablets 240mg . Cardizem CD capsules contain an active ingredient called diltiazem hydrochloride. They are designed to release the active ingredient slowly so that it works over 24 hours and can be taken once a day (CD stands for "controlled delivery"). Cardizem CD capsules belong to a group of medicines called calcium channel blockers or calcium antagonists. They work by opening up blood vessels, which lowers blood pressure and lets more blood and oxygen reach the heart. They do not change the amount of calciu .