Common uses

Treating supraventricular tachycardia, a rhythm disturbance of the heart. It is also used for controlling heart rate response to other rhythm disturbances, specifically, atrial fibrillation and flutter. It may also be used for other conditions as determined by your doctor.
Diltiazem is a calcium channel blocker. It works by slowing the electrical conduction in the heart, slowing heart rate, and/or normalizing heart rhythm.


Before using

Check your blood pressure and pulse rate regularly; this is important while you are taking diltiazem. Ask your prescriber or health care professional what your blood pressure and pulse rate should be and when you should contact him or her.

You may feel dizzy or lightheaded. Do not drive, use machinery, or do anything that needs mental alertness until you know how diltiazem affects you. To reduce the risk of dizzy or fainting spells, do not sit or stand up quickly, especially if you are an older patient. Avoid alcoholic drinks; they can make you more dizzy or increase flushing and rapid heartbeats.

If you are going to have surgery, tell your prescriber or health care professional that you are taking diltiazem.

Do not suddenly stop taking diltiazem. Ask your prescriber or health care professional how to gradually reduce the dose.

Directions

This medication should be swallowed whole with a full glass of water unless your doctor directs you otherwise. May be taken with or without meals. This drug must be taken as directed if used to prevent chest pain. It is not effective if taken only when chest pain occurs. Do not stop taking this medication suddenly without your doctor's permission. Your dose may need to be gradually decreased.


Cautions

If you are taking Diltiazem for high blood pressure, remember that it does not cure the problem; it merely controls it. You may need to take a blood pressure medication for the rest of your life.
If you are taking Diltiazem for angina, do not stop suddenly. This can lead to an increase in your attacks.

If you have congestive heart failure or suffer from kidney or liver disease, use Diltiazem with caution.
This medication may cause your heart rate to become too slow. You should check your pulse regularly.

Possible side effects

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat. Call your doctor at once if you have any of these serious side effects:
• fast or slow heartbeats;
• feeling light-headed, fainting;
• fever, sore throat, and headache with a severe blistering, peeling, and red skin rash;
• feeling short of breath, even with mild exertion;
• swelling, rapid weight gain; or
• nausea, stomach pain, low fever, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).
Less serious side effects may include:
• stuffy nose;
• skin rash or itching;
• dizziness, headache, tired feeling;
• nausea; or
• warmth, itching, redness, or tingly feeling under your skin.


If you take too much

Seek emergency medical attention if you think you have used too much of this medicine.
Overdose symptoms may include slow heartbeat, weakness, chest pain, shortness of breath, feeling light-headed, or fainting.

Additional information

Diltiazem can cause side effects that may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be awake and alert. Avoid drinking alcohol while taking diltiazem.
Grapefruit and grapefruit juice may interact with diltiazem and lead to potentially dangerous effects. Discuss the use of grapefruit products with your doctor. Do not increase or decrease the amount of grapefruit products in your diet without first talking to your doctor.


Drug interactions

Do not take Diltiazem with any of the following: alfuzosin; astemizole; cisapride; grapefruit juice; pimozide; terfenadine.

Diltiazem may also interact with the following medications: alosetron; antiinflammatory drugs (NSAIDs, such as ibuprofen); aspirin; barbiturates such as phenobarbital; bosentan; certain antibiotics (clarithromycin, erythromycin, norfloxacin, telithromycin, troleandomycin); certain medicines used to treat cancer; certain medicines to treat migraine (ergotamine, dihydroergotamine, methysergide); cevimeline; cilostazol; cimetidine; clonidine; cyclosporine; fentanyl; galantamine; herbal or dietary supplements such as ginger, gingko biloba, ginseng, hawthorn, ma huang (ephedra), melatonin, St. John's wort, went yeast; lithium; local anesthetics or general anesthetics; medicines for anxiety or difficulty sleeping (examples: alprazolam, buspirone, midazolam, triazolam); medicines for depression or mental problems (imipramine, fluoxetine, fluvoxamine, nefazodone, ziprasidone); medicines for fungal infections (fluconazole, itraconazole, ketoconazole, voriconazole); medicines for heart-rhythm problems (amiodarone, digoxin, disopyramide, dofetilide, encainide, flecainide, moricizine, procainamide, quinidine); medicines for high cholesterol (atorvastatin, cerivastatin, colesevelam, lovastatin, simvastatin); medicines for high blood pressure or heart problems; medicines for HIV infection or AIDS; medicines for prostate problems; medicines for seizures (carbamazepine, clonazepam, ethosuximide, phenobarbital, phenytoin, primidone, zonisamide); methadone; quinine; rifampin, rifabutin, or rifapentine; sildenafil; sirolimus; tacrolimus; theophylline or aminophylline; water pills (diuretics); yohimbine; zafirlukast; zileuton.