Diltiazem belongs to a class of medications called calcium channel blockers. This medication is used to treat mild-to-moderate high blood pressure and chronic stable angina (chest pain). Diltiazem works by relaxing blood vessels and by reducing the workload of the heart. It may take up to 2 to 4 weeks to see the full effects of this medication.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

The usual recommended starting dose of diltiazem extended-release tablets ranges from 180 mg daily to 240 mg daily. The maximum daily dose is 360 mg.

This medication should be taken once daily, at bedtime. It may be taken with or without food, but you should take the medication in the same way every time (always with food or always without food). Swallow the tablet whole with a glass of water – do not crush or chew the tablet.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from moisture, and keep it out of the reach of children.

180 mg
Each white, capsule-shaped tablet, debossed with "180" on one side, and a symbol and code "691" on the other side, contains 180 mg of diltiazem hydrochloride. Nonmedicinal ingredients: candelilla wax, colloidal silicone dioxide, corn starch, ethylcellulose, microcrystalline cellulose, eudragit, hypromellose, lactose monohydrate, magnesium stearate, polysorbate, polyethylene oxide, povidone, sugar, talc, titanium dioxide, and triacetin.

240 mg
Each white, capsule-shaped tablet, debossed with "240" on one side, and a symbol and code "692" on the other side, contains 240 mg of diltiazem hydrochloride. Nonmedicinal ingredients: candelilla wax, colloidal silicone dioxide, corn starch, ethylcellulose, microcrystalline cellulose, eudragit, hypromellose, lactose monohydrate, magnesium stearate, polysorbate, polyethylene oxide, povidone, sugar, talc, titanium dioxide, and triacetin.

300 mg
Each white, capsule-shaped tablet, debossed with "300" on one side, and a symbol and code "693" on the other side, contains 300 mg of diltiazem hydrochloride. Nonmedicinal ingredients: candelilla wax, colloidal silicone dioxide, corn starch, ethylcellulose, microcrystalline cellulose, eudragit, hypromellose, lactose monohydrate, magnesium stearate, polysorbate, polyethylene oxide, povidone, sugar, talc, titanium dioxide, and triacetin.

360  mg
Each white, capsule-shaped tablet, debossed with "360" on one side, and a symbol and code "694" on the other side, contains 360 mg of diltiazem hydrochloride. Nonmedicinal ingredients: candelilla wax, colloidal silicone dioxide, corn starch, ethylcellulose, microcrystalline cellulose, eudragit, hypromellose, lactose monohydrate, magnesium stearate, polysorbate, polyethylene oxide, povidone, sugar, talc, titanium dioxide, and triacetin.

Do not take diltiazem extended-release tablets if you:

• are allergic to diltiazem or any ingredients of the medication
• are or may become pregnant
• have certain types of heart rhythm problems (sick sinus syndrome, or second or third-degree AV block) and do not use a pacemaker
• have fluid in the lungs due to severe heart failure
• have very low blood pressure
• have a very slow heart rate
• are taking the medication dantrolene
• are taking the medication ivabradine

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• dizziness or lightheadedness
• flushing
• general feeling of being unwell
• headache
• heartburn
• nausea
• sore, red eyes
• vision changes

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• chest pain
• irregular or fast, pounding heartbeat
• low blood pressure (dizziness or lightheadedness when rising from a sitting or lying position)
• signs of depression (feeling sad, losing interest in things you used to enjoy, weight changes, changes in sleep habits, feelings of guilt or worthlessness, thoughts of suicide)
• signs of heart failure (e.g., shortness of breath, leg swelling, fatigue or excessive difficulty breathing with exercise)
• signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
• slow heartbeat
• swelling of ankles, feet, or lower legs
• symptoms of ear, nose, or throat infection (e.g., fever, sore throat, cough inflammation of the nose or throat)
• symptoms of high blood sugar (e.g., frequent urination, increased thirst, excessive eating, unexplained weight loss, poor wound healing, infections, fruity breath odour)
• unusual tiredness or weakness

Stop taking the medication and seek immediate medical attention if any of the following occur:

• signs of heart block (interruption of the normal electrical function in the heart; lightheadedness, fainting, irregular heartbeat)
• signs of a severe skin reaction (e.g., blistering, peeling, a rash covering a large area of the body, a rash that spreads quickly, or a rash combined with fever or discomfort)
• symptoms of a serious allergic reaction (e.g., hives, difficulty breathing, swelling of the face and throat)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should take this medication.

Blood pressure: Occasionally, blood pressure drops too low after taking this medication. Diltiazem extended-release tablets may cause dizziness and a drop in blood pressure when you stand from a sitting or lying down position, especially if you are taking medications that lower blood pressure. Get up slowly from a sitting or lying down position while you are taking this medication. If you experience lightheadedness, weakness, or dizziness, talk to your doctor.

Congestive heart failure: Diltiazem extended-release tablets may make symptoms of congestive heart failure worse. People who have had recent heart attacks may also be at increased risk. If you have congestive heart failure or have had a recent heart attack, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Diabetes: Diltiazem extended-release tablets may cause an increase in blood glucose. People with diabetes may find it necessary to monitor their blood sugar more frequently while using this medication. If you have diabetes or are at risk for developing diabetes, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Heart rhythm problems: For people with certain types of heart rhythm problems (e.g., sick sinus syndrome, second- and third-degree atrioventricular block), diltiazem extended-release tablets may cause abnormally slow heart rates. If you have one of these heart rhythm problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

If you have heart rhythm problems, do not use this medication if you do not use a pacemaker.

Kidney function: If you have reduced kidney function or kidney disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. People taking diltiazem have reportd cases of kidney injury. Conditions such as low blood pressure, slow heartbeat, or heart failure may increase the risk of kidney problems.

Liver function: Liver disease or reduced liver function may cause this medication to build up in the body, causing side effects. If you have reduced liver function or liver disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Your doctor will monitor your liver function closely while you are taking this medication.

Diltiazem extended-release tablets may cause a decrease in liver function. If you experience symptoms of liver problems (itchy rash, yellowing of the eyes or skin, dark urine, vomiting, upper right abdominal pain), stop taking this medication and contact your doctor immediately.

Pregnancy: This medication should not be used during pregnancy. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication passes into breast milk. If you are breast-feeding and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children.

Seniors: People 65 years or older may experience more side effects than younger people. Your doctor will monitor you closely while you are taking this medication.

For a full list of interactions, use the Drug Interaction Checker available on the Drugs.com website.

If you are taking other medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications that you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.