Verapamil (Calan): Uses, Side Effects, and Warnings

ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.

Overview

It's also used off-label to prevent cluster headaches.

What it's used for

High blood pressure
Chest pain (angina)
Some fast heart rhythms like SVT and AFib
Off-label: cluster headache prevention

How to take it

Take extended-release forms with food. Swallow them whole unless the label says they can be opened.
Don't switch between forms without asking.

Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.

Side effects

Common side effects

Constipation
Dizziness
Headache
Swollen ankles
Slow heartbeat

Call 911Fainting or a very slow heartbeat

Call your provider todayShortness of breath or fast weight gain

Call your provider todayYellow skin or eyes

Warnings

Not used with some types of heart failure or heart block.

Other medicines, foods, and alcohol

Beta blockers, digoxin, and amiodarone can slow the heart too much.
It raises levels of some statins, colchicine, dabigatran, and many others.
Grapefruit juice raises its level.
Alcohol effects may be stronger.

Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.

Pregnancy and breastfeeding

Talk with your provider.

Missed doses, overdose, and storage

If you miss a dose

Take it as soon as you remember, unless it's almost time for your next dose. Then skip the missed dose. Don't take two doses at once.

If someone takes too much

Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.

Storing it

Store at room temperature, away from heat and moisture (not in the bathroom), and out of reach of children and pets.

Conditions it's used for

Sources

Last updated 2026-11-13.

Verapamil