Diltiazem is used to prevent the symptoms of angina (chest pain). It belongs to a group of drugs known as calcium channel blockers. It is unclear exactly how it does so, but diltiazem dilates the blood vessels of the heart and increases the amount of oxygen that reaches the heart muscle. This drug is also prescribed to lower blood pressure in patients who have a history of hypertension.

Diltiazem Facts
Brand names (manufacturers): Cardizem (Biovail); Cardizem CD (Biovail); Cardizem SR (Biovail); Dilacor XR (Watson); diltiazem (various manufacturers); Tiazac (Forest); Tiazac ER (Forest)

Type of drug: Antianginal and antihypertensive

Ingredient: Diltiazem

Dosage forms: Extended-release capsules (120 mg, 180 mg, 240 mg, 300 mg, 360 mg, and 420 mg); tablets (30 mg, 60 mg, 90 mg, and 120 mg); sustained-release capsules (60 mg, 90 mg, and 120 mg)

Storage: Each of the various forms of this medication should be stored at room temperature in a tightly closed container.

Treatment

If stomach irritation occurs, diltiazem can be taken on an empty stomach or with meals, as directed by your doctor.

Swallow the sustained-release and extended-release capsules whole; chewing, crushing, or crumbling them destroys their controlled-release activity and possibly increases the side effects.

To become accustomed to taking this medication, try to take it at the same times each day. Although diltiazem does not relieve chest pain once the pain has begun, this medication can be used to prevent angina attacks.

If you miss a dose of diltiazem, take the missed dose as soon as possible, unless it is within four hours of the next scheduled dose. In that case, do not take the missed dose at all; just return to your regular dosing schedule. Do not double the next dose.

This medication does not cure angina or hypertension, but it will help to control the condition as long as you continue to take it.

Side Effects

Minor: Constipation, diarrhea, dizziness, drowsiness, headache, insomnia, light-headedness, nausea, nervousness, stomach upset, or vomiting. These side effects should disappear as your body adjusts to diltiazem.

 Diltiazem can increase your sensitivity to sunlight. Therefore, avoid prolonged exposure to sunlight and sunlamps. Wear protective clothing and sunglasses, and use an effective sunscreen.

If you feel dizzy or light-headed, sit or lie down for a while; get up slowly from a sitting or reclining position; and be careful on stairs. To avoid dizziness when you stand, relax and contract the muscles of your legs for a few moments before rising. Do this by pushing one foot against the floor while raising the other foot slightly, alternating feet so that you are "pumping" your legs in a pedaling motion.

To relieve constipation, increase the amount of fiber in your diet (fresh fruits and vegetables, salads, bran, and whole-grain breads), exercise, and drink more water (unless your doctor directs you to do otherwise).

Major: Tell your doctor about any side effects that are persistent or particularly bothersome. IT IS ESPECIALLY IMPORTANT TO TELL YOUR DOCTOR about confusion, depression, fainting, fatigue, flushing of the face, hallucinations, palpitations, skin rash, swelling of the hands and feet, tingling in the fingers or toes, unusual weakness, or yellowing of the eyes or skin.

Interactions

Diltiazem can interact with several other medications:
  • Diltiazem should be used cautiously with beta blockers (acebutolol, atenolol, betaxolol, carteolol, esmolol, labetalol, metoprolol, nadolol, penbutolol, propranolol, pindolol, and timolol), digitoxin, digoxin, or disopyramide. Side effects on the heart may be increased by the concurrent use of these medications.

  • Cimetidine can reduce the elimination of diltiazem from the body, increasing the risk of side effects.

  • Diltiazem can increase the blood concentrations of carbamazepine and cyclosporine, which can increase the risk of side effects.

  • Varying effects have been reported when this medication is taken concurrently with lithium; tell your doctor if you are taking both lithium and diltiazem.
BE SURE TO TELL YOUR DOCTOR about any medications you are currently taking, especially any listed above.

Warnings
  • Tell your doctor about unusual or allergic reactions you have had to any medications, especially to diltiazem.

  • Be sure to tell your doctor if you now have or ever had bradycardia (slow heartbeat), heart block, heart failure, kidney disease, liver disease, low blood pressure, or sick sinus syndrome.

  • If this medication makes you dizzy or drowsy, avoid taking part in any activity that requires alertness, such as driving an automobile or operating potentially dangerous equipment.

  • To prevent fainting while taking this drug, avoid drinking large amounts of alcohol. Also avoid prolonged standing and strenuous exercise in hot weather.

  • Be sure to tell your doctor if you are pregnant. Extensive studies in pregnant women have not been conducted, but birth defects have been reported in the offspring of animals that received large doses of diltiazem during pregnancy. It is also known that diltiazem passes into breast milk. If you are breast-feeding an infant while being treated with this medication, tell your doctor.