Diltiazem
A non-dihydropyridine calcium channel blocker used for high blood pressure, angina and, by injection, fast atrial fibrillation.
Drug card
- How it works
- Blocking calcium channels in heart and arteries, so the heart slows
- Used for
- High blood pressure
- Angina
- Fast atrial fibrillation or flutter, given IV
- Ending supraventricular tachycardia, given IV
- Known for
- Slow heart rate (bradycardia)
- AV block (heart block)
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does diltiazem work?
Diltiazem, a benzothiazepine, blocks slow calcium channels in heart and vascular muscle. It lengthens the AV node's refractory period, lowers the resting heart rate slightly, and dilates coronary and peripheral arteries, stopping coronary spasm. It is a CYP3A4 inhibitor with heavy first-pass metabolism; desacetyldiltiazem is its main metabolite.
Like other non-dihydropyridine calcium channel blockers: They block L-type (slow) calcium channels in the heart as well as in arterioles. The SA and AV nodes depend on calcium entry for their electrical activity, so the heart rate and AV conduction slow; heart muscle contracts less forcefully; and widened arterioles lower blood pressure and the heart's workload.
Uses
What is diltiazem used for?
- High blood pressure
- Angina
- Fast atrial fibrillation or flutter, given IV
- Ending supraventricular tachycardia, given IV
- Raynaud's phenomenon
Side effects
Side effects of diltiazem
- Slow heart rate (bradycardia)Known for
- AV block (heart block)Known forSerious
- Swollen hands, ankles or feet
- Headache
- Dizziness
- Constipation
- Flushing
- Palpitations
- Low blood pressure, most often with the injection
- Worsening heart failureSerious
- Acute liver injury (rare)Serious
- Stevens-Johnson syndrome or exfoliative dermatitis (rare)Serious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Contraindicated in sick sinus syndrome and 2nd- or 3rd-degree AV block unless paced, in hypotension, and in heart attack with lung congestion.
- With beta blockers or digoxin, the slowing of conduction adds up; IV diltiazem and IV beta blockers are not given close together.
- As a CYP3A4 inhibitor it raises simvastatin and lovastatin (myopathy risk), carbamazepine and ciclosporin levels.
Good to know: The NHS also lists it for Raynaud's phenomenon and, as a cream or ointment, for healing anal fissures.
Remember it
A way to remember it
Verapamil and diltiazem put the brakes on the heart.
Unlike the dihydropyridines, which mostly widen arteries, these two slow the SA and AV nodes and weaken contraction. That is why they control fast rhythms, and why bradycardia, heart block and heart failure are their dangers, above all with a beta blocker.
Written for biofideX
Its class
Non-dihydropyridine calcium channel blockers
Other non-dihydropyridine calcium channel blockers with a card:
Easily mixed up with dihydropyridine calcium channel blockers and beta blockers.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Diltiazem hydrochloride extended-release capsules: label (DailyMed)
- Diltiazem hydrochloride injection: label (DailyMed)
- Diltiazem (NCI Thesaurus)
- Diltiazem (NHS)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Blood pressure
Diltiazem is one of 27 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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