Diltiazem

What is diltiazem?

Diltiazem is a prescription-only calcium channel blocker used to treat various heart and blood vessel conditions. It works by relaxing the muscles of your heart and blood vessels, making it easier for your heart to pump and improving blood flow. It’s available under several brand names, including Adizem, Angitil, Tildiem, Viazem, and Zemtard[1]. 

What is diltiazem used for?

Doctors may prescribe diltiazem to treat the following conditions[1]: 

• High blood pressure (hypertension) 

• Angina (chest pain) 

• Certain irregular heart rhythms, such as atrial fibrillation (off-label indication) 

• Reduce the frequency of attacks in Raynaud’s phenomenon 

• Anal fissures (as a cream)  

How does diltiazem work?

Diltiazem works by blocking calcium from entering the muscle cells of the heart and blood vessels. It relaxes blood vessels, lowering blood pressure, it reduces the heart’s workload, which helps relieve angina and it slows the heart rate, which is useful in treating arrhythmias[1]. 

Who can take diltiazem?

Most adults and children over 12 years old can take diltiazem, but it may not be suitable for everyone. Avoid or use with caution if you[1]: 

• Are allergic to diltiazem or any of the ingredients listed as part of your medicine 

• Are pregnant, trying to get pregnant, or breastfeeding 

• Have liver or kidney disease 

• Have heart failure or a slow or irregular heartbeat 

• Have low blood pressure 

• Have digestive motility disorders or porphyria 

Please tell your doctor or pharmacist about any conditions you may have or medication you take before you start treatment, and always follow the instructions in the Patient Information Leaflet[2].  

How do you take diltiazem?

For the tablets or capsules, take diltiazem with or without food, at the same times every day. You should swallow both whole, usually with a glass of water, and never crush or chew them. If you find swallowing tablets or capsules difficult, speak to your doctor who can look into other forms for you[1]. 

For the cream or ointment, apply the 2.5cm length of diltiazem to the broken skin on the anus after bowel movements, twice a day for 6-8 weeks and following instructions on the packaging[1]. 

What is the typical dosage of diltiazem?

Diltiazem comes as tablets or capsules to treat high blood pressure, angina or Raynaud's. It's also available as a cream or ointment to treat anal fissures. The dosage depends on the condition being treated and the form of diltiazem you take. You should always take the same brand of diltiazem once you’ve started[1]: 

• Standard tablets: 60mg, taken 3 to 4 times daily, maximum 360 mg per day 

• Slow-release capsules/tablets: Dependent on the brand and condition treating, can range from 60mg to 180mg twice daily or 120mg to 500mg once daily 

• Cream or ointment for anal fissures: Apply a 2.5cm strip twice daily for 6 to 8 weeks 

Always follow your doctor or pharmacist’s instructions and stick to the same brand when possible. 

Can you stop taking diltiazem?

You should not stop taking diltiazem suddenly without consulting your doctor or pharmacist. Doing so may cause your blood pressure to rise or worsen angina symptoms, increasing the risk of heart attack or stroke[1]. 

What do you do if you take too much diltiazem?

Taking too much diltiazem can cause serious symptoms such as dizziness, fainting, slow or irregular heartbeat. Contact 111 for advice if you take more than your prescribed dose, if you need to go to A&E, do not drive, ask someone else to drive or call 999 [1]. 

What do you do if you forget to take diltiazem?

If you forget a dose, take it as soon as you remember unless it is close to your next scheduled dose[1]. 

• For once-daily dosing: Take as soon as you remember unlessits less than 12 hours before the next one, in which case skip the missed dose 

• For twice-daily dosing:Take as soon as you remember unless its less than 4 hours before the next dose, in which case skip the missed dose 

• For three times a day dosing: skip the missed dose and take the next dose at the usual time 

• Never double up on doses 

What medicines can’t you take with diltiazem?

Diltiazem may interact with the following substances[1]: 

• Beta-blockers (e.g. atenolol) 

• Statins (e.g. simvastatin) 

• Digoxin 

• Amiodarone 

• Antifungals (e.g. itraconazole, ketoconazole) 

• HIV or hepatitis C medication 

• Immunosuppressants (e.g. ciclosporin, tacrolimus) 

• Antibiotics (e.g. rifampicin, clarithromycin, erythromycin) 

• Epilepsy medication (e.g. carbamazepine, phenytoin) 

• Herbal supplements such as St John’s wort 

• Medicines for erectile dysfunction such as tadalafil 

Please note this is not a complete list, always inform your doctor or pharmacist about all medications and supplements you take before you start a new medicine, and follow the instructions in the Patient Information Leaflet[2]. 

What are the side effects of diltiazem?

Common side effects may include headache, dizziness, swollen ankles, flushing, tiredness, constipation. Serious side effects requiring medical help include slow heartbeat, fainting, severe stomach pain and yellowing of eyes or skin[1]. 

You should contact your GP if you experience any of these symptoms. In rare cases, the medicine may cause a serious allergic reaction (anaphylaxis). You should call 999 or visit A&E immediately if you believe this is happening[1]. 

Symptoms of anaphylaxis include[1]:  

• Difficulty breathing  

• Tightness in throat and chest  

• Swelling of the tongue or throat  

• Feeling faint or dizzy  

• Blue/grey skin or lips  

• Loss of consciousness 

If you experience any side effects, including those not listed, you are encouraged to report them via the Yellow Card Scheme or contact your doctor, pharmacist, or nurse. This information is intended as a summary for general awareness and does not replace professional medical advice. 

The information provided in the side effects section is not a comprehensive list of all possible side effects associated with this medication. For a complete list of side effects, please refer to the Patient Information Leaflet (PIL) provided with your medication or consult your healthcare professional[2]. 

Frequently asked questions about diltiazem

Can I drink alcohol with diltiazem? 
Yes, but only in moderation – alcohol can increase side effects like dizziness[1]. 

Can I drive while taking diltiazem? 
Yes, unless you feel dizzy or tired[1]. 

Is it safe in pregnancy or breastfeeding? 
It is not usually recommended – consult your doctor or pharmacist[1]. 

What if I see a whole tablet in my stool? 
This can happen with some slow-release forms – do not worry, it’s just the empty shell[1]. 

Will I need to take it forever? 
Possibly, especially for conditions like high blood pressure or angina[1]. 

For the official NHS guide to diltiazem, visit their website.