Verapamil
A non-dihydropyridine calcium channel blocker that slows the AV node, used for angina, fast heart rhythms and high blood pressure.
Drug card
- How it works
- Blocking calcium channels in heart and arteries, so the heart slows
- Used for
- Angina, including vasospastic and unstable angina
- Rate control in atrial fibrillation or flutter
- Preventing repeated supraventricular tachycardia
- High blood pressure
- Known for
- Constipation, its most common side effect
- 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 verapamil work?
Verapamil, a phenylalkylamine, blocks slow calcium channels in the AV node, lengthening its refractory period and slowing conduction; it also weakens heart muscle contraction and widens arterioles. Heavy first-pass metabolism leaves 20 to 35% bioavailable, and its metabolite norverapamil has about a fifth of its activity.
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 verapamil used for?
- Angina, including vasospastic and unstable angina
- Rate control in atrial fibrillation or flutter
- Preventing repeated supraventricular tachycardia
- High blood pressure
Side effects
Side effects of verapamil
- Constipation, its most common side effectKnown for
- Slow heart rate (bradycardia)Known for
- AV block (heart block)Known forSerious
- Heart failure or pulmonary edemaSerious
- Low blood pressure
- Dizziness
- Headache
- Nausea
- Ankle swelling (edema)
- Flushing
- Liver injury, from raised enzymes to hepatitisSerious
- Gum overgrowth (gingival hyperplasia), rare
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Never with atrial fibrillation or flutter plus an accessory pathway (WPW): risk of very fast ventricular rates or ventricular fibrillation.
- With a beta blocker: risk of severe bradycardia, heart block and heart failure.
- It raises digoxin levels by 50 to 75% and simvastatin exposure about 2.5-fold, and can increase lithium neurotoxicity.
- Liver disease slows its metabolism and stretches its half-life to 14 to 16 hours.
Good to know: Constipation is its best-known side effect; the NHS notes that specialists also use it to prevent cluster headaches.
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:
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
Verapamil 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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